Do you want to subscribe?
Subscribe today.Cancel Subscribe
Title: An Agricultural Testament (1943)Author: Sir Albert Howard
SIR ALBERT HOWARD, C.I.E., M.A.Formerly Director of the Institute of Plant Industry Indore,and Agricultural Adviser to States in Central India and Rajputana
TOGABRIELLEWHO IS NO MORE
The Earth, that's Nature's Mother, is her tomb; What is her burying grave, that is her womb.
Romeo and Juliet.
And Nature, the old nurse, took The child upon her knee, Saying: 'Here is a story-book Thy Father has written for thee.'
'Come, wander with me,' she said, 'Into regions yet untrod; And read what is still unread In the manuscripts of God.'
LONGFELLOWThe Fiftieth Birthday of Agassiz.
Since the Industrial Revolution the processes of growth have beenspeeded up to produce the food and raw materials needed by thepopulation and the factory. Nothing effective has been done to replacethe loss of fertility involved in this vast increase in crop and animalproduction. The consequences have been disastrous. Agriculture hasbecome unbalanced: the land is in revolt: diseases of all kinds are onthe increase: in many parts of the world Nature is removing the worn-outsoil by means of erosion.
The purpose of this book is to draw attention to the destruction of theearth's capital--the soil; to indicate some of the consequences of this;and to suggest methods by which the lost fertility can be restored andmaintained. This ambitious project is founded on the work and experienceof forty years, mainly devoted to agricultural research in the WestIndies, India, and Great Britain. It is the continuation of an earlierbook--The Waste Products of Agriculture, published in 1931--in which theIndore method for maintaining soil fertility by the manufacture of humusfrom vegetable and animal wastes was described.
During the last nine years the Indore Process has been taken up at manycentres all over the world. Much additional information on the role ofhumus in agriculture has been obtained. I have also had the leisure tobring under review the existing systems of farming as well as theorganization and purpose of agricultural research. Some attention hasalso been paid to the bio-dynamic methods of agriculture in Holland andin Great Britain, but I remain unconvinced that the disciples of RudolphSteiner can offer any real explanation of natural laws or have yetprovided any practical examples which demonstrate the value of theirtheories.
The general results of all this are set out in this my AgriculturalTestament. No attempt has been made to disguise the conclusions reachedor to express them in the language of diplomacy. On the contrary, theyhave been stated with the utmost frankness. It is hoped that they will bediscussed with the same freedom and that they will open up new lines ofthought and eventually lead to effective action.
It would not have been possible to have written this book without thehelp and encouragement of a former colleague in India, Mr. George Clarke,C.I.E., who held the post of Director of Agriculture in the UnitedProvinces for ten years (1921-31). He very generously placed at mydisposal his private notes on the agriculture of the Provinces covering aperiod of over twenty years, and has discussed with me during the lastthree years practically everything in this book. He read many of theChapters when they were first drafted, and made a number of suggestionswhich have been incorporated in the text.
Many who are engaged in practical agriculture all over the world and whohave adopted the Indore Process have contributed to this book. In a fewcases mention of this assistance has been made in the text. It isimpossible to refer to all the correspondents who have furnished progressreports and have so freely reported their results. These provided aninvaluable collection of facts and observations which has amply confirmedmy own experience.
Great stress has been laid on a hitherto undiscovered factor innutrition--the mycorrhizal association--the living fungous bridge betweenhumus in the soil and the sap of plants. The existence of such asymbiosis was first suggested to me on reading an account of theremarkable results with conifers, obtained by Dr. M. C. Rayner at Warehamin Dorset in connexion with the operations of the Forestry Commission. Ifmycorrhiza occurs generally in the plantation industries and also in ourcrops, an explanation of such things as the development of quality,disease resistance, and the running out of the variety, as well as theslow deterioration of the soil which follows the use of artificialmanures, would be provided. I accordingly took steps to collect a widerange of specimens likely to contain mycorrhiza, extending over the wholeof tropical and temperate agriculture. I am indebted to Dr. Rayner and toDr. Ida Levisohn for the detailed examination of this material. They havefurnished me with many valuable and suggestive technical reports. For theinterpretation of these laboratory results, as set out in the followingpages, I am myself solely responsible.
I am indebted to a number of Societies for permission to reproduceinformation and illustrations which have already been published. Twoother organizations have allowed me to incorporate results which mightwell have been regarded as confidential. The Royal Society of London haspermitted me to reprint, in the Chapter on Soil Aeration, a precis of anillustrated paper which appeared in their Proceedings. The Royal Societyof Arts has provided the blocks for the section on sisal waste. The RoyalSanitary Institute has agreed to the reproduction in full of a paper readat the Health Congress, held at Portsmouth in July 1938. The BritishMedical Journal has placed at my disposal the information contained in anarticle by Dr. Lionel J. Picton, O.B.E. The publishers of Dr. Waksman'smonograph on Humus have allowed me to reprint two long extracts relatingto the properties of humus. Messrs. Arthur Guinness, Sons & Co., Limited,have agreed to the publication of the details of the composting of townwastes in their hop garden at Bodiam. Messrs. Walter Duncan & Co. haveallowed the Manager of the Gandrapara Tea Garden to contribute anillustrated article on the composting of wastes on this fine estate.Captain J. M. Moubray has sent me a very interesting summary of the workhe is doing at Chipoli in Southern Rhodesia, which is given in AppendixB.
In making the Indore Process widely known, a number of journals haverendered yeoman service. In Great Britain The Times and the Journal ofthe Royal Society of Arts have published a regular series of letters andarticles. In South Africa the Farmer's Weekly has from the beginningurged the agricultural community to increase the humus content of thesoil. In Latin America the planters owe much to the Revista del Institutode Defensa del Cafe de Costa Rica.
Certain of the largest tea companies in London, Messrs. James Finlay &Co., Walter Duncan & Co., the Ceylon Tea Plantations Company, Messrs.Octavius Steel & Co., and others, most generously made themselvesresponsible over a period of two years for a large part of the officeexpenses connected with the working out and application to the plantationindustries of the Indore Process. They also defrayed the expenses of atour to the tea estates of India and Ceylon in 1937. These arrangementswere very kindly made on my behalf by Mr. G. H. Masefield, Chairman ofthe Ceylon Tea Plantations Company.
In the work of reducing to order the vast mass of correspondence andnotes on soil fertility' which have accumulated, and in getting the bookinto its final shape, I owe much to the ability and devotion of myprivate secretary, Mrs. V. M. Hamilton.
A. H. BLACKHEATH,1 January 1940
In deciding to issue a fifth reprint of my late husband's book,An Agricultural Testament, I have abstained from introducing any additionsor corrections. To do so would necessitate an almost complete rewritingof this, the first and perhaps the most trenchant, statement of his views.Nevertheless, it would be incorrect to deny that the subject matterstreated progressed rapidly even in the course of his own life time; hehimself added to what he said here, and many gallant writers have followedhis lead. A survey of literature presents difficulties, partly owing toSir Albert Howard's practice of scattering articles in journals all overthe world. Following on the creation of an Albert Howard Foundation ofOrganic Husbandry, the declared aim of which is to continue and makeknown the Albert Howard principles, inquiries may be addressed tothe Headquarters of the Foundation at Sharnden Manor, Mayfield, Sussex,England.
LOUISE E. HOWARD1949
PART I THE PART PLAYED BY SOIL FERTILITY IN AGRICULTURE
II. THE NATURE OF SOIL FERTILITY.III. THE RESTORATION OF FERTILITY.
PART II THE INDORE PROCESS
IV. THE INDORE PROCESSV. PRACTICAL APPLICATIONS OF THE INDORE PROCESSVI. DEVELOPMENTS OF THE INDORE PROCESSVII. DEVELOPMENTS OF THE INDORE PROCESS, GRASS-LAND MANAGEMENTVIII. DEVELOPMENTS OF THE INDORE PROCESS, THE UTILIZATION OF TOWN WASTES
PART III HEALTH, INDISPOSITION, AND DISEASE IN AGRICULTURE
IX. SOIL AERATIONX. SOME DISEASES OF THE SOILXI. THE RETREAT OF THE CROP AND THE ANIMAL BEFORE THE PARASITEXII. SOIL FERTILITY AND NATIONAL HEALTH.
PART IV AGRICULTURAL RESEARCH
XIII. A CRITICISM OF PRESENT-DAY AGRICULTURAL RESEARCHXIV. A SUCCESSFUL EXAMPLE OF AGRICULTURAL RESEARCH
PART V CONCLUSIONS AND SUGGESTIONS
XV. A FINAL SURVEY
A. COMPOST MANUFACTURE ON A TEA ESTATE IN BENGALB. COMPOST MAKING AT CHIPOLI, SOUTHERN RHODESIAC. THE MANUFACTURE OF HUMUS FROM THE WASTES OF THE TOWN AND THE VILLAGE
The maintenance of the fertility of the soil is the first condition ofany permanent system of agriculture. In the ordinary processes of cropproduction fertility is steadily lost: its continuous restoration bymeans of manuring and soil management is therefore imperative.
In the study of soil fertility the first step is to bring under reviewthe various systems of agriculture which so far have been evolved. Thesefall into four main groups: (1) the methods of Nature--the supremefarmer--as seen in the primeval forest, in the prairie, and in the ocean;(2) the agriculture of the nations which have passed away; (3) thepractices of the Orient, which have been almost unaffected by Westernscience; and (4) the methods in vogue in regions like Europe and NorthAmerica to which a large amount of scientific attention has been paidduring the last hundred years.
NATURE'S METHODS OF SOIL MANAGEMENT
Little or no consideration is paid in the literature of agriculture tothe means by which Nature manages land and conducts her water culture.Nevertheless, these natural methods of soil management must form thebasis of all our studies of soil fertility.
What are the main principles underlying Nature's agriculture? These canmost easily be seen in operation in our woods and forests.
Mixed farming is the rule: plants are always found with animals: manyspecies of plants and of animals all live together. In the forest everyform of animal life, from mammals to the simplest invertebrates, occurs.The vegetable kingdom exhibits a similar range: there is never anyattempt at monoculture: mixed crops and mixed farming are the rule.
The soil is always protected from the direct action of sun, rain, andwind. In this care of the soil strict economy is the watchword: nothingis lost. The whole of the energy of sunlight is made use of by thefoliage of the forest canopy and of the undergrowth. The leaves alsobreak up the rainfall into fine spray so that it can the more easily bedealt with by the litter of plant and animal remains which provide thelast line of defence of the precious soil. These methods of protection,so effective in dealing with sun and rain, also reduce the power of thestrongest winds to a gentle air current.
The rainfall in particular is carefully conserved. A large portion isretained in the surface soil: the excess is gently transferred to thesubsoil and in due course to the streams and rivers. The fine spraycreated by the foliage is transformed by the protective ground litterinto thin films of water which move slowly downwards, first into thehumus layer and then into the soil and subsoil. These latter have beenmade porous in two ways: by the creation of a well-marked crumb structureand by a network of drainage and aeration channels made by earthworms andother burrowing animals. The pore space of the forest soil is at itsmaximum so that there is a large internal soil surface over which thethin films of water can creep. There is also ample humus for the directabsorption of moisture. The excess drains away slowly by way of thesubsoil. There is remarkably little run-off, even from the primeval rainforest. When this occurs it is practically clear water. Hardly any soilis removed. Nothing in the nature of soil erosion occurs. The streams andrivers in forest areas are always perennial because of the vast quantityof water in slow transit between the rainstorms and the sea. There istherefore little or no drought in forest areas because so much of therainfall is retained exactly where it is needed. There is no wasteanywhere.
The forest manures itself. It makes its own humus and supplies itselfwith minerals. If we watch a piece of woodland we find that a gentleaccumulation of mixed vegetable and animal residues is constantly takingplace on the ground and that these wastes are being converted by fungiand bacteria into humus. The processes involved in the early stages ofthis transformation depend throughout on oxidation: afterwards they takeplace in the absence of air. They are sanitary. There is no nuisance ofany kind--no smell, no flies, no dustbins, no incinerators, no artificialsewage system, no water-borne diseases, no town councils, and no rates.On the contrary, the forest affords a place for the ideal summer holiday:sufficient shade and an abundance of pure fresh air. Nevertheless, allover the surface of the woods the conversion of vegetable and animalwastes into humus is never so rapid and so intense as during the holidaymonths--July to September.
The mineral matter needed by the trees and the undergrowth is obtainedfrom the subsoil. This is collected in dilute solution in water by thedeeper roots, which also help in anchoring the trees. The details of rootdistribution and the manner in which the subsoil is thoroughly combed forminerals are referred to in a future chapter. Even in soils markedlydeficient in phosphorus trees have no difficulty in obtaining amplesupplies of this element. Potash, phosphate, and other minerals arealways collected in situ and carried by the transpiration current for usein the green leaves. Afterwards they are either used in growth ordeposited on the floor of the forest in the form of vegetable waste--oneof the constituents needed in the synthesis of humus. This humus is againutilized by the roots of the trees. Nature's farming, as seen in theforest, is characterized by two things: (1) a constant circulation of themineral matter absorbed by the trees; (2) a constant addition of newmineral matter from the vast reserves held in the subsoil. There istherefore no need to add phosphates: there is no necessity for morepotash salts. No mineral deficiencies of any kind occur. The supply ofall the manure needed is automatic and is provided either by humus or bythe soil. There is a natural division of the subject into organic andinorganic. Humus provides the organic manure: the soil the mineralmatter.
The soil always carries a large fertility reserve. There is no hand tomouth existence about Nature's farming. The reserves are carried in theupper layers of the soil in the form of humus. Yet any uselessaccumulation of humus is avoided because it is automatically mingled withthe upper soil by the activities of burrowing animals such as earthwormsand insects. The extent of this enormous reserve is only realized whenthe trees are cut down and the virgin land is used for agriculture. Whenplants like tea, coffee, rubber, and bananas are grown on recentlycleared land, good crops can be raised without manure for ten years ormore. Like all good administrators, therefore, Nature carries strongliquid reserves effectively invested. There is no squandering of thesereserves to be seen anywhere.
The crops and live stock look after themselves. Nature has never found itnecessary to design the equivalent of the spraying machine and the poisonspray for the control of insect and fungous pests. There is nothing inthe nature of vaccines and serums for the protection of the live stock.It is true that all kinds of diseases are to be found here and thereamong the plants and animals of the forest, but these never assume largeproportions. The principle followed is that the plants and animals canvery well protect themselves even when such things as parasites are to befound in their midst. Nature's rule in these matters is to live and letlive.
If we study the prairie and the ocean we find that similar principles arefollowed. The grass carpet deals with the rainfall very much as theforest does. There is little or no soil erosion: the run-off ispractically clear water. Humus is again stored in the upper soil. Thebest of the grassland areas of North America carried a mixed herbagewhich maintained vast herds of bison. No veterinary service was inexistence for keeping these animals alive. When brought into cultivationby the early settlers, so great was the store of fertility that theseprairie soils yielded heavy crops of wheat for many years without livestock and without manure.
In lakes, rivers, and the sea mixed farming is again the rule: a greatvariety of plants and animals are found living together: nowhere does onefind monoculture. The vegetable and animal wastes are again dealt with byeffective methods. Nothing is wasted. Humus again plays an important partand is found everywhere in solution, in suspension, and in the depositsof mud. The sea, like the forest and the prairie, manures itself.
The main characteristic of Nature's farming can therefore be summed up ina few words. Mother earth never attempts to farm without live stock; shealways raises mixed crops; great pains are taken to preserve the soil andto prevent erosion; the mixed vegetable and animal wastes are convertedinto humus; there is no waste; the processes of growth and the processesof decay balance one another; ample provision is made to maintain largereserves of fertility; the greatest care is taken to store the rainfall;both plants and animals are left to protect themselves against disease
In considering the various man-made systems of agriculture, which so farhave been devised, it will be interesting to see how far Nature'sprinciples have been adopted, whether they have ever been improved upon,and what happens when they are disregarded.
THE AGRICULTURE OF THE NATIONS WHICH HAVE PASSED AWAY
The difficulties inherent in the study of the agriculture of the nationswhich are no more are obvious. Unlike their buildings, where it ispossible from a critical study of the buried remains of cities toreproduce a picture of bygone civilizations, the fields of the ancientshave seldom been maintained. The land has either gone back to forest orhas been used for one system of farming after another.
In one case, however, the actual fields of a bygone people have beenpreserved together with the irrigation methods by which these lands weremade productive. No written records, alas, have come down to us of thestaircase cultivation of the ancient Peruvians, perhaps one of the oldestforms of Stone Age agriculture. This arose either in mountains or in theupland areas under grass because of the difficulty, before the discoveryof iron, of removing the dense forest growth. In Peru irrigated staircasefarming seems to have reached its highest known development. More thantwenty years ago the National Geographical Society of the United Statessent an expedition to study the relics of this ancient method ofagriculture, an account of which was published by O. F. Cook in theSociety's Magazine of May 1916, under the title: 'Staircase Farms of theAncients.' The system of the megalithic people of old Peru was toconstruct a stairway of terraced fields up the slopes of the mountains,tier upon tier, sometimes as many as fifty in number. The outer retainingwalls of these terraces were made of large stones which fit into oneanother with such accuracy that even at the present day, like those ofthe Egyptian pyramids, a knife blade cannot be inserted between them.After the retaining wall was built, the foundation of the future fieldwas prepared by means of coarse stones covered with clay. On this basislayers of soil, several feet thick, originally imported from beyond thegreat mountains, were super-imposed and then levelled for irrigation. Thefinal result was a small flat field with only just sufficient slope forartificial watering. In other words, a series of huge flower pots, eachprovided with ample drainage below, was prepared with incredible labourby this ancient people for their crops. Such were the megalithicachievements in agriculture, beside which 'our undertakings sink intoinsignificance in face of what this vanished race accomplished. Thenarrow floors and steep walls of rocky valleys that would appear utterlyworthless and hopeless to our engineers were transformed, literally madeover, into fertile lands and were the homes of teeming populations inpre-historic days' (O. F. Cook). The engineers of old Peru did what theydid through necessity because iron, steel, reinforced concrete, and themodern power units had not been invented. The plunder of the forest soilwas beyond their reach.
These terraced fields had to be irrigated. Water had to be led to themover immense distances by means of aqueducts. Prescott states that onewhich traversed the district of Condesuyu measured between four and fivehundred miles. Cook gives a photograph of one of these channels as a thindark line traversing a steep mountain wall many hundreds of feet abovethe valley.
These ancient methods of agriculture are represented at the present dayby the terraced cultivation of the Himalayas, of the mountainous areas ofChina and Japan, and of the irrigated rice fields so common in the hillsof South India, Ceylon, and the Malayan Archipelago. Conway'sdescription, published in 1894, of the terraces of Hunza on theNorth-West Frontier of India and of the canal, carried for long distancesacross the face of precipices to the one available supply of perennialwater--the torrent from the Ultor glacier--tallies almost completely withwhat he found in 1901 in the Bolivian Andes. This distinguished scholarand mountaineer considered that the native population of Hunza of thepresent day is living in a stage of civilization that must bear no littlelikeness to that of the Peruvians under Inca government. An example ofthis ancient method of farming has thus been preserved through the ages.In a future chapter the relation which exists between the nutritionalvalue of the food grown on these irrigated terraces and the health of thepeople will be discussed. This relic of the past is interesting from thepoint of view of quality in food as well as from its historical value.
Some other systems of agriculture of the past have come down to us in theform of written records which have furnished ample material forconstructive research. In the case of Rome in particular a fairlycomplete account of the position of agriculture, from the period of themonarchy to the fall of the Roman Empire, is available; the facts can beconveniently followed in the writings of Mommsen, Heitland, and otherscholars. In the case of Rome the Servian Reform (Servius Tullius,578-534 B.C.) shows very clearly not only that the agricultural classoriginally preponderated in the State but also that an effort was made tomaintain the collective body of freeholders as the pith and marrow of thecommunity. The conception that the constitution itself rested on thefreehold system permeated the whole policy of Roman war and conquest. Theaim of war was to increase the number of its freehold members.
'The vanquished community was either compelled to merge entirely intothe yeomanry of Rome, or, if not reduced to this extremity, it wasrequired, not to pay a war contribution or a fixed tribute, but to cedea portion, usually a third part, of its domain, which was thereuponregularly occupied by Roman farms. Many nations have gained victoriesand made conquests as the Romans did; but none has equalled the Roman inthus making the ground he had won his own by the sweat of his brow, andin securing by the ploughshare what had been gained by the lance. Thatwhich is gained by war may be wrested from the grasp by war again, butit is not so with the conquests made by the plough; whilst the Romanslost many battles, they scarcely ever on making peace ceded Roman soil,and for this result they were indebted to the tenacity with which thefarmers clung to their fields and homesteads. The strength of man and ofthe State lies in their dominion over the soil; the strength of Rome wasbuilt on the most extensive and immediate mastery of her citizens overthe soil, and on the compact unity of the body which thus acquired sofirm a hold.' (Mommsen.)
These splendid ideals did not persist. During the period which elapsedbetween the union of Italy and the subjugation of Carthage, a gradualdecay of the farmers set in; the small-holdings ceased to yield anysubstantial clear return; the cultivators one by one faced ruin; themoral tone and frugal habits of the earlier ages of the Republic werelost; the land of the Italian farmers became merged into the largerestates. The landlord capitalist became the centre of the subject. Henot only produced at a cheaper rate than the farmer because he had moreland, but he began to use slaves. The same space which in the oldentime, when small-holdings prevailed, had supported from a hundred to ahundred and fifty families was now occupied by one family of freepersons and about fifty, for the most part unmarried, slaves. 'If thiswas the remedy by which the decaying national economy was to be restoredto vigour, it bore, unhappily, an aspect of extreme resemblance todisease' (Mommsen). The main causes of this decline appear to have beenfourfold: the constant drain on the manhood of the country-side by thelegions, which culminated in the two long wars with Carthage; theoperations of the Roman capitalist landlords which 'contributed quite asmuch as Hamilcar and Hannibal to the decline in the vigour and thenumber of the Italian people' (Mommsen); failure to work out a balancedagriculture between crops and live stock and to maintain the fertilityof the soil; the employment of slaves instead of free labourers. Duringthis period the wholesale commerce of Latium passed into the hands ofthe large landed proprietors who at the same time were the speculatorsand capitalists. The natural consequence was the destruction of themiddle classes, particularly of the small-holders, and the developmentof landed and moneyed lords on the one hand and of an agriculturalproletariat on the other. The power of capital was greatly enhanced bythe growth of the class of tax-farmers and contractors to whom the Statefarmed out its indirect revenues for a fixed sum. Subsequent politicaland social conflicts did not give real relief to the agriculturalcommunity. Colonies founded to secure Roman sovereignty over Italyprovided farms for the agricultural proletariat, but the root causes ofthe decline in agriculture were not removed in spite of the efforts ofCato and other reformers. A capitalist system of which the apparentinterests were fundamentally opposed to a sound agriculture remainedsupreme. The last half of the second century saw degradation and moreand more decadence. Then came Tiberius Gracchus and the Agrarian Lawwith the appointment of an official commission to counteract thediminution of the farmer class by the comprehensive establishment of newsmall-holdings from the whole Italian landed property at the disposal ofthe State: eighty thousand new Italian farmers were provided with land.These efforts to restore agriculture to its rightful place in the Statewere accompanied by many improvements in Roman agriculture which,unfortunately, were most suitable for large estates. Land no longer ableto produce corn became pasture; cattle now roamed over large ranches;the vine and the olive were cultivated with commercial success. Thesesystems of agriculture, however, had to be carried on with slave labour,the supply of which had to be maintained by constant importation. Suchextensive methods of farming naturally failed to supply sufficient foodfor the population of Italy. Other countries were called upon to furnishessential foodstuffs; province after province was conquered to feed thegrowing proletariat with corn. These areas in turn slowly yielded to thesame decline which had taken place in Italy. Finally the wealthy classesabandoned the depopulated remnants of the mother country and builtthemselves a new capital at Constantinople. The situation had to besaved by a migration to fresh lands. In their new capital the Romansrelied on the unexhausted fertility of Egypt as well as on that of AsiaMinor and the Balkan and Danubian provinces.
Judged by the ordinary standards of achievement the agricultural historyof the Roman Empire ended in failure due to inability to realize thefundamental principle that the maintenance of soil fertility coupled withthe legitimate claims of the agricultural population should never havebeen allowed to come in conflict with the operations of the capitalist.The most important possession of a country is its population. If this ismaintained in health and vigour everything else will follow; if this isallowed to decline nothing, not even great riches, can save the countryfrom eventual ruin. It follows, therefore, that the strongest possiblesupport of capital must always be a prosperous and contentedcountry-side. A working compromise between agriculture and finance shouldtherefore have been evolved. Failure to achieve this naturally ended inthe ruin of both.
THE PRACTICES OF THE ORIENT
In the agriculture of Asia we find ourselves confronted with a system ofpeasant farming which in essentials soon became stabilized. What ishappening to-day in the small fields of India and China took place manycenturies ago. There is here no need to study historical records or topay a visit to the remains of the megalithic farming of the Andes. Theagricultural practices of the Orient have passed the supreme test--theyare almost as permanent as those of the primeval forest, of the prairieor of the ocean. The small-holdings of China, for example, are stillmaintaining a steady output and there is no loss of fertility after fortycenturies of management. What are the chief characteristics of thisEastern farming?
The holdings are minute. Taking India as an example, the relation betweenman power and cultivated area is referred to in the Census Report of 1931as follows: 'For every agriculturalist there is 2.9 acres of cropped landof which 0.65 of an acre is irrigated. The corresponding figures of 1921are 2.7 and 0.61.' These figures illustrate how intense is the strugglefor existence in this portion of the tropics. These small-holdings areoften cultivated by extensive methods (those suitable for large areas)which utilize neither the full energies of man or beast nor the potentialfertility of the soil.
If we turn to the Far East, to China and Japan, a similar system ofsmall-holdings is accompanied by an even more intense pressure ofpopulation both human and bovine. In the introduction to FARMERS OF FORTYCENTURIES, King states that the three main islands of Japan had in 1907 apopulation of 46,977,000, maintained on 20,000 square miles of cultivatedfields. This is at the rate of 2,349 to the square mile or more thanthree people to each acre. In addition, Japan fed on each square mile ofcultivation a very large animal population--69 horses and 56 cattle,nearly all employed in labour; 825 poultry; 13 swine, goats, and sheep.Though no accurate statistics are available in China, the examples quotedby King reveal a condition of affairs not unlike that in Japan. In theShantung Province a farmer with a family of twelve kept one donkey, onecow, and two pigs on 2.5 acres of cultivated land--a density ofpopulation at the rate of 3,072 people, 256 donkeys, 256 cattle, and 512pigs per square mile. The average of seven Chinese holdings visited gavea maintenance capacity of 1,783 people, 212 cattle or donkeys, and 399pigs--nearly 2,000 consumers and 400 rough food transformers per squaremile of farmed land. In comparison with these remarkable figures, thecorresponding statistics for 1900 in the case of the United States persquare mile were: population 61, horses and mules 30.
Food and forage crops are predominant. The primary function of Easternagriculture is to supply the cultivators and their cattle with food. Thisautomatically follows because of the pressure of the population on theland: the main hunger the soil has to appease is that of the stomach. Asubsidiary hunger is that of the machine which needs raw materials formanufacture. This extra hunger is new but has developed considerablysince the opening of the Suez Canal in 1869 (by which the small fields ofthe cultivator have been brought into effective contact with the marketsof the West) and the establishment of local industries like cotton andjute. To both these hungers soil fertility has to respond. We know fromlong experience that the fields of India can respond to the hunger of thestomach. Whether they can fulfil the added demands of the machine remainsto be seen. The Suez Canal has only been in operation for seventy years.The first cotton mill in India was opened in 1818 at Fort Gloster, nearCalcutta. The jute industry of Bengal has grown up within a century. Jutewas first exported in 1838. The first jute mill on the Hoogly beganoperations in 1855. These local industries as well as the export trade inraw products for the use of the factories of the West are an extra drainon soil fertility. Their future well-being and indeed their veryexistence is only possible provided adequate steps are taken to maintainthis fertility. There is obviously no point in establishing cotton andjute mills in India, in founding trading agencies like those of Calcuttaand in building ships for the conveyance of raw products unless suchenterprises are stable and permanent. It would be folly and an obviouswaste of capital to pursue such activities if they are founded only onthe existing store of soil fertility. All concerned in the hunger of themachine--government, financiers, manufacturers, and distributors--mustsee to it that the fields of India are equal to the new burden which hasbeen thrust upon her during the last fifty years or so. The demands ofcommerce and industry on the one hand and the fertility of the soil onthe other must be maintained in correct relation the one to the other.
The response of India to the two hungers--the stomach and themachine--will be evident from a study of Table I, in which the area inacres under food and fodder crops is compared with that under moneycrops.
The chief food crops in order of importance are rice, pulses millets,wheat, and fodder crops. The money crops are more varied; cotton and oilseeds are the most important, followed by jute and other fibres, tobacco,tea, coffee, and opium. It will be seen that food and fodder cropscomprise 86 per cent. of the total area under crops and that money crops,as far as extent is concerned, are less important, and constitute onlyone-seventh of the total cultivated area.
Agricultural Statistics of British India, 1935-6Area, in acres, under food and fodder crops
Rice 79,888,000Millets 38,144,000Wheat 25,150,000Gram 14,897,000Pulses and other food grains 29,792,000Fodder crops 10,791,000Condiments, spices, fruits, vegetablesand miscellaneous food crops 8,308,000Barley 6,178,000Maize 6,211,000Sugar 4,038,000
Total food and fodder crops 223,397,000
Area, in acres, under money crops
Cotton 15,761,000Oil seeds, chiefly ground-nuts,sesamum, rape, mustard and linseed 15,662,000Jute and other fibres 2,706,000Dyes, tanning materials, drugs,narcotics, and miscellaneous 1,458,000Tobacco 1,230,000Tea 787,000Coffee 97,000Indigo 40,000Opium 10,000
Total money crops 37,751,000
One interesting change in the production of Indian food crops has takenplace during the last twenty-five years. The output of sugar used to beinsufficient for the towns, and large quantities were imported from Java,Mauritius, and the continent of Europe. To-day, thanks to the work atShahjahanpur in the United Provinces, the new varieties of cane bred atCoimbatore and the protection now enjoyed by the sugar industry, India isalmost self-supporting as far as sugar is concerned. The pre-war averageamount of sugar imported was 634,000 tons; in 1937-8 the total had fallento 14,000 tons.
Mixed crops are the rule. In this respect the cultivators of the Orienthave followed Nature's method as seen in the primeval forest. Mixedcropping is perhaps most universal when the cereal crop is the mainconstituent. Crops like millets, wheat, barley, and maize are mixed withan appropriate subsidiary pulse, sometimes a species that ripens muchlater than the cereal. The pigeon pea (Cajanus indicus Spreng.), perhapsthe most important leguminous crop of the Gangetic alluvium, is growneither with millets or with maize. The mixing of cereals and pulsesappears to help both crops. When the two grow together the character ofthe growth improves. Do the roots of these crops excrete materials usefulto each other? Is the mycorrhizal association found in the roots of thesetropical legumes and cereals the agent involved in this excretion?Science at the moment is unable to answer these questions: she is onlynow beginning to investigate them Here we have another instance where thepeasants of the East have anticipated and acted upon the solution of oneof the problems which Western science is only just beginning torecognize. Whatever may be the reason why crops thrive best whenassociated in suitable combinations, the fact remains that mixturesgenerally give better results than monoculture. This is seen in GreatBritain in the growth of dredge corn, in mixed crops of wheat and beans,vetches and rye, clover and rye-grass, and in intensive vegetable growingunder glass. The produce raised under Dutch lights has noticeablyincreased since the mixed cropping of the Chinese vegetable growers ofAustralia has been copied. (Mr. F. A. Secrett was, I believe, the firstto introduce this system on a large scale into Great Britain. He informedme that he saw it for the first time at Melbourne.)
A balance between live stock and crops is always maintained. Althoughcrops are generally more important than animals in Eastern agriculture,we seldom or never find crops without animals. This is because oxen arerequired for cultivation and buffaloes for milk. (The buffalo is themilch cow of the Orient and is capable not only of useful labour in thecultivation of rice, but also of living and producing large quantities ofrich milk on a diet on which the best dairy cows of Europe and Americawould starve. The acclimatization of the Indian buffalo in the villagesof the Tropics--Africa, Central America, the West Indies inparticular--would do much to improve the fertility of the soil and thenutrition of the people.)
Nevertheless, the waste products of the animal, as is often the case inother parts of the world, are not always fully utilized for the land. TheChinese have for ages past recognized the importance of the urine ofanimals and the great value of animal wastes in the preparation ofcomposts. In India far less attention is paid to these wastes and a largeportion of the cattle dung available is burnt for fuel. On the otherhand, in most Oriental countries human wastes find their way back to theland. In China these are collected for manuring the crops direct. InIndia they are concentrated on the zone of highly manured landimmediately round each village. If the population or a portion of itcould be persuaded to use a more distant zone for a few years, the areaof village lands under intensive agriculture could at least be doubled.Here is an opportunity for the new system of government in India to raiseproduction without the expenditure of a single rupee. In India there are500,000 villages each of which is surrounded by a zone of very fertileland which is constantly being over-manured by the habits of the people.If we examine the crops grown on this land we find that the yields arehigh and the plants are remarkably free from disease. Although half amillion examples of the connexion between a fertile soil and a healthyplant exist in India alone, and these natural experiments have been inoperation for centuries before experiment stations like Rothamsted wereever thought of, modern agricultural science takes no notice of theresults and resolutely refuses to accept them as evidence, largelybecause they lack the support furnished by the higher mathematics. Theyalso dispose of one of the ideas of the disciples of Rudolph Steiner, whoargue that the use of human wastes in agriculture is harmful.
Leguminous plants are common. Although it was not till 1888, after aprotracted controversy lasting thirty years, that Western science finallyaccepted as proved the important part played by pulse crops in enrichingthe soil, centuries of experience had taught the peasants of the East thesame lesson. The leguminous crop in the rotation is everywhere one oftheir old fixed practices. In some areas, such as the Indo-Gangeticplain, one of these pulses--the pigeon pea--is also made use of as asubsoil cultivator. The deep spreading root system is used to promote theaeration of the closely packed silt soils, which so closely resemblethose of the Holland Division of Lincolnshire in Great Britain.
Cultivation is generally superficial and is carried out by wooden ploughsfurnished with an iron point. Soil-inverting ploughs, as used in the Westfor the destruction of weeds, have never been designed by Easternpeoples. The reasons for this appear to be two: (1) soil inversion forthe destruction of weeds is not necessary in a hot climate where the samework is done by the sun for nothing; (2) the preservation of the level ofthe fields is essential for surface drainage, for preventing localwaterlogging, and for irrigation. Another reason for this surfacecultivation has recently been pointed out. The store of nitrogen in thesoil in the form of organic matter has to be carefully conserved: it ispart of the cultivator's working capital. Too much cultivation and deepploughing would oxidize this reserve and the balance of soil fertilitywould soon be destroyed.
Rice is grown whenever possible. By far the most important crop in theEast is rice. In India, as has already been pointed out, the productionof rice exceeds that of any two food crops put together. Whenever thesoil and water supply permit, rice is invariably grown. A study of thiscrop is illuminating. At first sight rice appears to contradict one ofthe great principles of the agricultural science of the Occident, namely,the dependence of cereals on nitrogenous manures. Large crops of rice areproduced in many parts of India on the same land year after year withoutthe addition of any manure whatever. The rice fields of the countryexport paddy in large quantities to the centres of population or abroad,but there is no corresponding import of combined nitrogen.
Taking Burma as an example of an area exporting rice beyond seas, duringthe twenty years ending 1924, about 25,000,000 tons of paddy have beenexported from a tract roughly 10,000,000 acres in area. As unhusked ricecontains about 1.2 per cent. of nitrogen the amount of this element,shipped overseas during twenty years or destroyed in the burning of thehusk, is in the neighbourhood of 300,000 tons. As this constant drain ofnitrogen is not made up for by the import of manure, we should expect tofind a gradual loss of fertility. Nevertheless, this does not take placeeither in Burma or in Bengal, where rice has been grown on the same landyear after year for centuries. Clearly the soil must obtain freshsupplies of nitrogen from somewhere, otherwise the crop would cease togrow. The only likely source is fixation from the atmosphere, probably inthe submerged algal film on the surface of the mud. This is one of theproblems of tropical agriculture which is now being investigated.
Where does the rice crop obtain its nitrogen? One source in allprobability is fixation from the atmosphere in the submerged algal filmon the surface of the mud. Another is the rice nursery itself, where theseedlings are raised on land heavily manured with cattle dung. Largequantities of nitrogen and other nutrients are stored in the seedlingitself; this at transplanting time contains a veritable arsenal ofreserves of all kinds which carry the plant successfully through thisprocess and probably also furnish some of the nitrogen needed duringsubsequent growth. The manuring of the rice seedling illustrates a verygeneral principle in agriculture, namely, the importance of starting acrop in a really fertile soil and so arranging matters that the plant canabsorb a great deal of what it needs as early as possible in itsdevelopment.
There is an adequate supply of labour. Labour is everywhere abundant, aswould naturally follow from the great density of the rural population.Indeed, in India it is so great that if the leisure time of thecultivators and their cattle for a single year could be calculated asmoney at the local rates a perfectly colossal figure would be obtained.This leisure, however, is not altogether wasted. It enables thecultivators and their oxen to recover from the periods of intensive workwhich precede the sowing of the crops and which are needed at harvesttime. At these periods time is everything: everybody works from sunriseto sunset. The preparation of the land and the sowing of the crops needthe greatest care and skill; the work must be completed in a very shorttime so that a large labour force is essential.
It will be observed that in this peasant agriculture the great pressureof population on the soil results in poverty, most marked where, as inIndia, extensive methods are used on small-holdings which really needintensive farming. It is amazing that in spite of this unfavourablefactor soil fertility should have been preserved for centuries: this isbecause natural means have been used and not artificial manures. Thecrops are able to withstand the inroads of insects and fungi without athin film of protective poison.
THE AGRICULTURAL METHODS OF THE OCCIDENT
If we take a wide survey of the contribution which is being made by thefields of the West, we find that they are engaged in trying to satisfy noless than three hungers: (1) the local hunger of the rural population,including the live stock; (2) the hunger of the growing urban areas, thepopulation of which is unproductive from the point of view of soilfertility; and (3) the hunger of the machine avid for a constant streamof the raw materials required for manufacture. The urban populationduring the last century has grown out of all knowledge; the needs of themachine increase as it becomes more and more efficient; falling profitsare met by increasing the output of manufactured articles. All this addsto the burden on the land and to the calls on its fertility. It will notbe without interest to analyse critically the agriculture of the West andsee how it is fitting itself for its growing task. This can be done byexamining its main characteristics. These are as follows:
The holding tends to increase in size. There is a great variation in thesize of the agricultural holdings of the West from the small family unitsof France and Switzerland to the immense collective farms of Russia andthe spacious ranches of the United States and Argentina. Side by sidewith this growth in the size of the farm is the diminution of the numberof men per square mile. In Canada, for example, the number of workers per1,000 acres of cropped land fell from 26 in 1911 to 16 in 1926. Sincethese data were published the size of the working population has shrunkstill further. This state of things has arisen from the scarcity anddearness of labour which has naturally led to the study of labour-savingdevices.
Monoculture is the rule. Almost everywhere crops are grown in pureculture. Except in temporary leys, mixed crops are rare. On the richprairie lands of North America even rotations are unknown: crops of wheatfollow one another and no attempt is made to convert the straw into humusby means of the urine and dung of cattle. The straw is a tiresomeencumbrance and is burnt off annually.
The machine is rapidly replacing the animal. Increasing mechanization isone of the main features of Western agriculture. Whenever a machine canbe invented which saves human or animal labour its spread is rapid.Engines and motors of various kinds are the rule everywhere. Theelectrification of agriculture is beginning. The inevitable march of thecombine harvester in all the wheat-producing areas of the world is one ofthe latest examples of the mechanization of the agriculture of the West.Cultivation tends to be quicker and deeper. There is a growing feelingthat the more and the deeper the soil is stirred the better will be thecrop. The invention of the gyrotiller, a heavy and expensive soil churn,is one of the answers to this demand. The slaves of the Roman Empire havebeen replaced by mechanical slaves. The replacement of the horse and theox by the internal combustion engine and the electric motor is, however,attended by one great disadvantage. These machines do not void urine anddung and so contribute nothing to the maintenance of soil fertility. Inthis sense the slaves of Western agriculture are less efficient thanthose of ancient Rome.
Artificial manures are widely used. The feature of the manuring of theWest is the use of artificial manures. The factories engaged during theGreat War in the fixation of atmospheric nitrogen for the manufacture ofexplosives had to find other markets, the use of nitrogenous fertilizersin agriculture increased, until to-day the majority of farmers and marketgardeners base their manurial programme on the cheapest forms of nitrogen(N), phosphorus (P), and potassium (K) on the market. What may beconveniently described as the NPK mentality dominates farming alike inthe experimental stations and the country-side. Vested interests,entrenched in time of national emergency, have gained a stranglehold.
Artificial manures involve less labour and less trouble than farm-yardmanure. The tractor is superior to the horse in power and in speed ofwork: it needs no food and no expensive care during its long hours ofrest. These two agencies have made it easier to run a farm. Asatisfactory profit and loss account has been obtained. For the momentfarming has been made to pay. But there is another side to this picture.These chemicals and these machines can do nothing to keep the soil ingood heart. By their use the processes of growth can never be balanced bythe processes of decay. All that they can accomplish is the transfer ofthe soil's capital to current account. That this is so will be muchclearer when the attempts now being made to farm without any animals atall march to their inevitable failure.
Diseases are on the increase. With the spread of artificials and theexhaustion of the original supplies of humus, carried by every fertilesoil, there has been a corresponding increase in the diseases of cropsand of the animals which feed on them. If the spread of foot-and-mouthdisease in Europe and its comparative insignificance among well fedanimals in the East are compared, or if the comparison is made betweencertain areas in Europe, the conclusion is inevitable that there must bean intimate connexion between faulty methods of agriculture and animaldisease. In crops like potatoes and fruit, the use of the poison sprayhas closely followed the reduction in the supplies of farm-yard manureand the diminution of fertility.
Food preservation processes are also on the increase. A feature of theagriculture of the West is the development of food preservation processesby which the journey of products like meat, milk, vegetables, and fruitbetween the soil and the stomach is prolonged. This is done by freezing,by the use of carbon dioxide, by drying, and by canning. Although food ispreserved for a time in this way, what is the effect of these processeson the health of the community during a period of, say, twenty-fiveyears? Is it possible to preserve the first freshness of food? If so thenscience will have made a very real contribution.
Science has been called in to help production. Another of the features ofthe agriculture of the West is the development of agricultural science.Efforts have been made to enlist the help of a number of separatesciences in studying the problems of agriculture and in increasing theproduction of the soil. This has entailed the foundation of numerousexperiment stations which every year pour out a large volume of advice inthe shape of printed matter.
These mushroom ideas of agriculture are failing; mother earth deprived ofher manurial rights is in revolt; the land is going on strike; thefertility of the soil is declining. An examination of the areas whichfeed the population and the machines of a country like Great Britainleaves no doubt that the soil is no longer able to stand the strain. Soilfertility is rapidly diminishing, particularly in the United States,Canada, Africa, Australia, and New Zealand. In Great Britain itself realfarming has already been given up except on the best lands. The loss offertility all over the world is indicated by the growing menace of soilerosion. The seriousness of the situation is proved by the attention nowbeing paid to this matter in the press and by the variousAdministrations. In the United States, for example, the whole resourcesof government are being mobilized to save what is left of the good earth.
The agricultural record has been briefly reviewed from the standpoint ofsoil fertility. The main characteristics of the various methods ofagriculture have been summarized. The most significant of these are theoperations of Nature as seen in the forest. There the fullest use is madeof sunlight and rainfall in raising heavy crops of produce and at thesame time not only maintaining fertility but actually building up largereserves of humus. The peasants of China, who pay great attention to thereturn of all wastes to the land, come nearest to the ideal set byNature. They have maintained a large population on the land without anyfalling off in fertility. The agriculture of ancient Rome failed becauseit was unable to maintain the soil in a fertile condition. The farmers ofthe West are repeating the mistakes made by Imperial Rome. The soils ofthe Roman Empire, however, were only called upon to assuage the hunger ofa relatively small population. The demands of the machine were thenalmost non-existent. In the West there are relatively more stomachs tofill while the growing hunger of the machine is an additional burden onthe soil. The Roman Empire lasted for eleven centuries. How long will thesupremacy of the West endure? The answer depends on the wisdom andcourage of the population in dealing with the things that matter. Canmankind regulate its affairs so that its chief possession--the fertilityof the soil--is preserved? On the answer to this question the future ofcivilization depends.
Agricultural Statistics of India, 1, Delhi, 1938.
HOWARD, A., and HOWARD, G. L. C. The Development of IndianAgriculture, Oxford University Press, 1929.
KING, F. H. Farmers of Forty Centuries or Permanent Agriculturein China, Korea, and Japan, London, 1916.
LYMINGTON, VISCOUNT. Famine in England, London, 1938.
MOMMSEN, THEODOR. The History of Rome, transl. Dickson, London, 1894.
WRENCH, G. T. The Wheel of Health, London, 1938.
PART I THE PART PLAYED BY SOIL FERTILITY IN AGRICULTURE
THE NATURE OF SOIL FERTILITY
What is this soil fertility? What exactly does it mean? How does itaffect the soil, the crop, and the animal? How can we best investigateit? An attempt will be made in this chapter to answer these questions andto show why soil fertility must be the basis of any permanent system ofagriculture.
The nature of soil fertility can only be understood if it is consideredin relation to Nature's round. In this study we must at the outsetemancipate ourselves from the conventional approach to agriculturalproblems by means of the separate sciences and above all from thestatistical consideration of the evidence afforded by the ordinary fieldexperiment. Instead of breaking up the subject into fragments andstudying agriculture in piecemeal fashion by the analytical methods ofscience, appropriate only to the discovery of new facts, we must adopt asynthetic approach and look at the wheel of life as one great subject andnot as if it were a patchwork of unrelated things.
All the phases of the life cycle are closely connected; all are integralto Nature's activity; all are equally important; none can be omitted. Wehave therefore to study soil fertility in relation to a natural workingsystem and to adopt methods of investigation in strict relation to such asubject. We need not strive after quantitative results: the qualitativewill often serve. We must look at soil fertility as we would study abusiness where the profit and loss account must be taken along with thebalance-sheet, the standing of the concern, and the method of management.It is the 'altogetherness' which matters in business, not some particulartransaction or the profit or loss of the current year. So it is with soilfertility. We have to consider the wood, not the individual trees.
The wheel of life is made up of two processes--growth and decay. The oneis the counterpart of the other.
Let us first consider growth. The soil yields crops; these form the foodof animals: crops and animals are taken up into the human body and aredigested there. The perfectly grown, normal, vigorous human being is thehighest natural development known to us. There is no break in the chainfrom soil to man; this section of the wheel of life is uninterruptedthroughout; it is also an integration; each step depends on the last. Itmust therefore be studied as a working whole.
The energy for the machinery of growth is derived from the sun; thechlorophyll in the green leaf is the mechanism by which this energy isintercepted; the plant is thereby enabled to manufacture food--tosynthesize carbohydrates and proteins from the water and other substancestaken up by the roots and the carbon dioxide of the atmosphere. Theefficiency of the green leaf is therefore of supreme importance; on itdepends the food supply of this planet, our well-being, and ouractivities. There is no alternative source of nutriment. Without sunlightand the green leaf our industries, our trade, and our possessions wouldsoon be useless.
The chief factors on which the work of the green leaf depends are thecondition of the soil and its relation to the roots of the plant. Theplant and the soil come into gear by means of the root system in twoways--by the root hairs and by the mycorrhizal association. The firstcondition for this gearing is that the internal surface of the soil--thepore space--shall be as large as possible throughout the life of thecrop. It is on the walls of this pore space, which are covered with thinwater films, that the essential activities of the soil take place. Thesoil population, consisting mainly of bacteria, fungi and protozoa, carryon their life histories in these water films.
The contact between the soil and the plant which is best understood takesplace by means of the root hairs. These are prolongations of the outerlayer of cells of the young root. Their duty is to absorb from the thinfilms of moisture on the walls of the pore space the water and dissolvedsalts needed for the work of the green leaves: no actual food can reachthe plant in this way, only simple things which are needed by the greenleaf to synthesize food. The activities of the pore space depend onrespiration for which adequate quantities of oxygen are essential. Acorresponding amount of carbon dioxide is the natural by-product. Tomaintain the oxygen supply and to reduce the amount of carbon dioxide,the pore spaces must be kept in contact with the atmosphere. The soilmust be ventilated. Hence the importance of cultivation.
As most of the soil organisms possess no chlorophyll, and, moreover, haveto work in the dark, they must be supplied with energy. This is obtainedby the oxidation of humus--the name given to a complex residue of partlyoxidized vegetable and animal matter together with the substancessynthesized by the fungi and bacteria which break down these wastes. Thishumus also helps to provide the cement which enables the minute mineralsoil particles to aggregate into larger compound particles and somaintain the pore space. If the soil is deficient in humus, the volume ofthe pore space is reduced; the aeration of the soil is impeded; there isinsufficient organic matter for the soil population; the machinery of thesoil runs down; the supply of oxygen, water, and dissolved salts neededby the root hairs is reduced; the synthesis of carbohydrates and proteinsin the green leaf proceeds at a lower tempo; growth is affected. Humus istherefore an essential material for the soil if the first phase of thelife cycle is to function.
There is another reason why humus is important. Its presence in the soilis an essential condition for the proper functioning of the secondcontact between soil and plant--the mycorrhizal relationship. By means ofthis connexion certain soil fungi, which live on humus, are able toinvade the living cells of the young roots and establish an intimaterelation with the plant, the details of which symbiosis are still beinginvestigated and discussed. Soil fungus and plant cells live together incloser partnership than the algal and fungous constituents of the lichendo. How the fungus benefits has yet to be determined. How the plantprofits is easier to understand. If a suitable preparation of such rootsis examined under the microscope, all stages in the digestion of thefungous mycelium can be seen. At the end of the partnership the rootconsumes the fungus and in this manner is able to absorb thecarbohydrates and proteins which the fungus obtains partly from the humusin the soil. The mycorrhizal association therefore is the living bridgeby which a fertile soil (one rich in humus) and the crop are directlyconnected and by which food materials ready for immediate use can betransferred from soil to plant. How this association influences the workof the green leaf is one of the most interesting problems science has nowto investigate. Is the effective synthesis of carbohydrates and proteinsin the green leaf dependent on the digestion products of these soilfungi? It is more than probable that this must prove to be the case. Arethese digestion products at the root of disease resistance and quality?It would appear so. If this is the case it would follow that on theefficiency of this mycorrhizal association the health and well-being ofmankind must depend.
In a fertile soil the soil and the plant come into gear in two wayssimultaneously. In establishing and maintaining these contacts humus isessential. It is therefore a key material in the life cycle. Without thissubstance the wheel of life cannot function effectively.
The processes of decay which round off and complete the wheel of life canbe seen in operation on the floor of any woodland. This has already beendiscussed. It has been shown how the mixed animal and vegetable wastesare converted into humus and how the forest manures itself.
Such are the essential facts in the wheel of life. Growth on the oneside: decay on the other. In Nature's farming a balance is struck andmaintained between these two complementary processes. The only man-madesystems of agriculture--those to be found in the East--which have stoodthe test of time have faithfully copied this rule in Nature. It followstherefore that the correct relation between the processes of growth andthe processes of decay is the first principle of successful farming.Agriculture must always be balanced. If we speed up growth we mustaccelerate decay. If, on the other hand, the soil's reserves aresquandered, crop production ceases to be good farming: it becomessomething very different. The farmer is transformed into a bandit.
It is now possible to define more clearly the meaning of soil fertility.It is the condition of a soil rich in humus in which the growth processesproceed rapidly, smoothly, and efficiently. The term therefore connotessuch things as abundance, high quality, and resistance to disease. A soilwhich grows to perfection a wheat crop--the food of man--is describedfertile. A pasture on which meat and milk of the first class are producedfalls into the same category. An area under market-garden crops on whichvegetables of the highest quality are raised has reached the peak asregards fertility.
Why does soil fertility so markedly influence the soil, the plant, andthe animal? By virtue of the humus it contains. The nature and propertiesof this substance as well as the products of its decomposition aretherefore important. These matters must now be considered.
What is humus? A reply to this question has been rendered easier by theappearance in 1938 of the second edition of Waksman's admirable monographon humus in which the results of no less than 1311 original papers havebeen reduced to order. Waksman defines humus as
'a complex aggregate of brown to dark-coloured amorphous substances whichhave originated during the decomposition of plant and animal residues bymicro-organisms, under aerobic and anaerobic conditions, usually insoils, composts, peat bogs, and water basins. Chemically, humus consistsof various constituents of the original plant material resistant tofurther decomposition; of substances undergoing decomposition; ofcomplexes resulting from decomposition either by processes of hydrolysisor by oxidation and reduction; and of various compounds synthesized bymicro-organisms. Humus is a natural body; it is a composite entity, justas are plant, animal, and microbial substances; it is even much morecomplex chemically, since all these materials contribute to itsformation. Humus possesses certain specific physical, chemical, andbiological properties which make it distinct from other natural organicbodies. Humus, in itself or by interaction with certain inorganicconstituents of the soil, forms a complex colloidal system, the differentconstituents of which are held together by surface forces; this system isadaptable to changing conditions of reaction, moisture, and action byelectrolytes. The numerous activities of the soil micro-organisms takeplace in this system to a large extent.'
Viewed from the standpoint of chemistry and physics humus is thereforenot a simple substance: it is made up from a group of very complexorganic compounds depending on the nature of the residues from which itis formed, on the conditions under which decomposition takes place, andon the extent to which the processes of decay have proceeded. Humus,therefore, cannot be exactly the same thing everywhere. It is bound to bea creature of circumstance. Moreover it is alive and teems with a vastrange of micro-organisms which derive most of their nutriment from thissubstratum. Humus in the natural state is dynamic, not static. From thepoint of view of agriculture, therefore, we are dealing not with simpledead matter like a sack of sulphate of ammonia, which can be analysed andvalued according to its chemical composition, but with a vast organiccomplex in which an important section of the farmer's invisible labourforce--the organisms which carry on the work of the soil--is temporarilyhoused. Humus, therefore, involves the element of labour; in this respectalso it is one of the most important factors on the farm.
It is essential at this point to pay some attention to the manysidedproperties of humus and to realize how profoundly it differs from achemical manure. At the moment all over the world field trials--based onmere nitrogen content--are in progress for comparing, on the currentcrop, dressings of humus and various artificial manures. A mere glance atthe properties of humus will show that such field trials are based on afundamental misconception of what soil fertility implies and aremisleading and therefore useless.
The properties of humus have been summed up by Waksman as follows:
1. Humus possesses a dark brown to black colour.
2. Humus is practically insoluble in water, although a part of it may gointo colloidal solution in pure water. Humus dissolves to a large extentin dilute alkali solutions, especially on boiling, giving a dark colouredextract; a large part of this extract precipitates when the alkalisolution is neutralized by mineral acids.
3. Humus contains a somewhat larger amount of carbon than do plant,animal, and microbial bodies; the carbon content of humus is usuallyabout 55 to 56 per cent., and frequently reaches 58 per cent.
'4. Humus contains considerable nitrogen, usually about 3 to 6 per cent.The nitrogen concentration may be frequently less than this figure; inthe case of certain high-moor peats, for example, it may be only 0.5-0.8per cent. It may also be higher, especially in sub-soils, frequentlyreaching 10 to 12 per cent.
'5. Humus contains the elements carbon and nitrogen in proportions whichare close to 10:1; this is true of many soils and of humus in seabottoms. This ratio varies considerably with the nature of the humus, thestage of its decomposition, the nature and depth of soil from which it isobtained, the climatic and other environmental conditions under which itis formed.
6. Humus is not in a static, but rather in a dynamic, condition, since itis constantly formed from plant and animal residues and is continuouslydecomposed further by micro-organisms.
7. Humus serves as a source of energy for the development of variousgroups of micro-organisms, and during decomposition gives off acontinuous stream of carbon dioxide and ammonia.
8. Humus is characterized by a high capacity of base-exchange, ofcombining with various other soil constituents, of absorbing water, andof swelling, and by other physical and physico-chemical properties whichmake it a highly valuable constituent of substrates which support plantand animal life.'
To this list of properties must be added the role of humus as a cement increating and maintaining the compound soil particles so important in themaintenance of tilth.
The effect of humus on the crop is nothing short of profound. The farmersand peasants who live in close touch with Nature can tell by a glance atthe crop whether or not the soil is rich in humus. The habit of the plantthen develops something approaching personality; the foliage assumes acharacteristic set; the leaves acquire the glow of health; the flowersdevelop depth of colour; the minute morphological characters of the wholeof the plant organs become clearer and sharper. Root development isprofuse: the active roots exhibit not only turgidity but bloom.
The influence of humus on the plant is not confined to the outwardappearance of the various organs. The quality of the produce is alsoaffected. Seeds are better developed, and so yield better crops and alsoprovide live stock with a satisfaction not conferred by the produce ofworn-out land. The animals need less food if it comes from fertile soil.Vegetables and fruit grown on land rich in humus are always superior inquality, taste, and keeping power to those raised by other means. Thequality of wines, other things being equal, follows the same rule. Almostevery villager in countries like France appreciates these points and willtalk of them freely without the slightest prompting.
In the case of fodder a very interesting example of the relation betweensoil fertility and quality has recently been investigated. This wasnoticed in the meadows of La Crau between Salon and Aries in Provence.Here the fields are irrigated with muddy water, containing finely dividedlimestone drawn from the Durance, and manured mostly with farm-yardmanure. The soils are open and permeable, the land is well drainednaturally. All the factors on which soil fertility depends are presenttogether--an open soil with ample organic matter, ample moisture, and theideal climate for growth. Any grazier who saw these meadows for the firsttime would at once be impressed by them: a walk through the fields athay-making would prepare him for the news that it pays the owners ofhigh-quality animals to obtain their roughage from this distant source.Several cuts of hay are produced every year, which enjoy such areputation for quality that the bales are sent long distances by motorlorry to the various racing stables of France and are even exported toNewmarket. The small stomach of the racehorse needs the very best foodpossible. This the meadows of La Crau help to produce.
The origin of these irrigated meadows would provide an interesting story.Did they arise as the result of a set of permanent manurial experimentson the Broadbalk model or through the work of some observant localpioneer? I suspect the second alternative will be found to be nearer thetruth. A definite answer to this question is desirable because in arecent discussion at Rothamsted, on the relation between a fertile soiland high-quality produce, it was stated that no evidence of such aconnexion could be discovered in the literature. The farmers of Provence,however, have supplied it and also a measure of quality in the shape of asatisfactory price. For the present the only way of measuring qualityseems to be by selling it. It cannot be weighed and measured by themethods of the laboratory. Nevertheless it exists: moreover itconstitutes a very important factor in agriculture. Apparently some ofthe experiment stations have not yet come to grips with this factor: thefarmers have. The sooner therefore that effective liaison is establishedbetween these two agencies the better.
The effect of soil fertility on live stock can be observed in the field.As animals live on crops we should naturally expect the character of theplant as regards nutrition to be passed on to stock. This is so. Theeffect of a fertile soil can at once be seen in the condition of theanimals. This is perhaps most easily observed in the bullocks fattened onsome of the notable pastures in Great Britain. The animals show awell-developed bloom, the coat and skin look and feel right, the eyes areclear, bright, and lively. The posture of the animal betokens health andwell-being. It is not necessary to weigh or measure them. A glance on thepart of a successful grazier, or of a butcher accustomed to deal withhigh-class animals, is sufficient to tell them whether all is well orwhether there is something wrong with the soil or the management of theanimals or both. The results of a fertile soil and proper methods ofmanagement are measured by the prices these animals fetch in the marketand the standing of the farmer in these markets. It should be acompulsory item in the training of agricultural investigators toaccompany some of the best of our English cattle from the pasture to themarket and watch what happens there. They would at once discover that themost fertile pastures produce the best animals, that auctioneers andbuyers detect quality instantly, and that such animals find a ready saleand command the best prices. The reputation of the pastures is finallypassed on to the butcher and to his clients.
Resistance to insect and fungous disease is also conferred by humus.Perhaps the best examples of this are to be seen in the East. In India,the crops grown on the highly fertile soils round the 500,000 villagessuffer remarkably little from pests. This subject is developed at lengthin a future chapter when the retreat of the crop and of the animal beforethe parasite is discussed.
Soil fertility not only influences crops and live stock but also thefauna of the locality. This is perhaps most easily seen in the fish ofstreams which flow through areas of widely differing degrees offertility. An example of such difference is referred to at the end ofChapter V of Isaac Walton's COMPLEAT ANGLER the following words:
'And so I shall proceed next to tell you, it is certain, that certainfields near Leominster, a town in Herefordshire, are observed to makesheep that graze upon them more fat than the next, and also to bear finerwool; that is to say, that in that year in which they feed in such aparticular pasture, they shall yield finer wool than they did that yearbefore they came to feed in it, and coarser again if they shall return totheir former pasture; and again return to a finer wool, being fed in thefine wool ground. Which I tell you, that you may the better believe thatI am certain, if I catch a trout in one meadow he shall be white andfaint, and very likely to be lousy; and as certainly if I catch a troutin the next meadow, he shall be strong and red and lusty and much bettermeat: trust me, scholar. I have caught many a trout in a particularmeadow, that the very shape and enamelled colour of him hath been such ashath joyed me to look on him: and I have then with much pleasureconcluded with Solomon, "Everything is beautiful in his season".'
Soil fertility is the condition which results from the operation ofNature's round, from the orderly revolution of the wheel of life, fromthe adoption and faithful execution of the first principle ofagriculture--there must always be a perfect balance between the processesof growth and the processes of decay. The consequences of this conditionare a living soil, abundant crops of good quality, and live stock whichpossess the bloom of health. The key to a fertile soil and a prosperousagriculture is humus.
RAYNER, M. C. Mycorrhiza: an Account of Non-pathogenic Infectionby Fungi in Vascular Plants and Bryophytes, London, 1927.
---------'Mycorrhiza in relation to Forestry', Forestry, viii,1934, p. 96; x, 1936, p. 1; and xiii, 1939, p. 19.
WAKSMAN, S. A. Humus: Origin, Chemical Composition, and Importancein Nature, London, 1938.
THE RESTORATION OF FERTILITY
The moment mankind undertook the business of raising crops and breedinganimals, the processes of Nature were subjected to interference. Soilfertility was exploited for the growing of food and the production of theraw materials--such as wool, skins, and vegetable fibres--needed forclothing. Up to the dawn of the Industrial Revolution in the West, thelosses of humus involved in these agricultural operations were made upeither by the return of waste material to the soil or by taking up virginland.
Where the return of wastes balanced the losses of humus involved inproduction, systems of agriculture became stabilized and there was noloss of fertility. The example of China has already been quoted. The oldmixed farming of a large part of Europe, including GreatBritain--characterized by a correct balance between arable and livestock, the conversion of wastes into farmyard manure, methods of sheepfolding, and the copious use of the temporary ley--is another instance ofthe same thing.
The constant exploitation of new areas to replace worn-out land has alsogone on for centuries and is still taking place. Sometimes this hasinvolved wars and conquests: at other times nothing more than taking upfresh prairie or forest land wherever this was to be found. A specialmethod is adopted by some primitive tribes. The forest growth is burntdown, the store of humus is converted into crops, the exhausted land isgiven back to Nature for reafforestation and the building up of a newreserve of humus. In a rough and ready way fertility is maintained. Suchshifting cultivation still exists all over the world, but like the takingup of new land is only possible when the population is small and suitableland abundant. This burning process has even been incorporated intopermanent systems of agriculture and has proved of great value in ricecultivation in western India. Here the intractable soils of the ricenurseries have to be prepared during the last part of the hot season sothat the seedlings are ready for transplanting by the break of themonsoon. This is achieved by covering the nurseries with branchescollected from the forest and setting fire to the mass. The heat destroysthe colloids, restores the tilth, and makes the manuring and cultivationof the rice nurseries possible.
It is an easy matter to destroy a balanced agriculture. Once the demandfor food and raw materials increases and good prices are obtained for theproduce of the soil, the pressure on soil fertility becomes intense. Thetemptation to convert this fertility into money becomes irresistible.Western agriculture was subjected to this strain by the very rapiddevelopments which followed the invention of the steam-engine, theinternal combustion engine, electrically driven motors, and improvementsin communications and transport. Factory after factory arose; a demandfor labour followed; the urban population increased. All thesedevelopments provided new and expanding markets for food and rawmaterials. These were supplied in three ways--by cashing-in the existingfertility of the whole world, by the use of a temporary substitute forsoil fertility in the shape of artificial manures, and by a combinationof both methods. The net result has been that agriculture has becomeunbalanced and therefore unstable.
Let us review briefly the operations of Western agriculture from thepoint of view of the utilization of wastes in order to discover whetherthe gap between the losses and gains of humus, now bridged byartificials, can be reduced or abolished altogether. If this is possible,something can be done to restore the balance of agriculture and to makeit more stable and therefore more permanent.
Many sources of soil organic matter exist, namely: (1) the roots ofcrops, weeds, and crop residues which are turned under in the course ofcultivation; (2) the algae met with in the surface soil; (3) temporaryleys, the turf of worn-out grass land, catch crops, and green-manures;(4) the urine of animals; (5) farmyard manure; (6) the contents of thedustbins of our cities and towns; (7) certain factory wastes which resultfrom the processing of agricultural produce; (8) the wastes of the urbanpopulation; (9) water-weeds, including seaweed. These must now be verybriefly considered. In later chapters most of these matters will bereferred to again and discussed in greater detail.
THE RESIDUES TURNED UNDER IN THE COURSE OF CULTIVATION. It is not alwaysrealized that about half of every crop--the root system--remains in theground at harvest time and thus provides a continuous return of organicmatter to the soil. The weeds and their roots ploughed in during theordinary course of cultivation add to this supply. When these residues,supplemented by the fixation of nitrogen from the atmosphere, areaccompanied by skilful soil management, which safeguards the preciousstore of humus, crop production can be maintained at a low level withoutthe addition of any manure whatsoever beyond the occasional droppings oflive stock and birds. A good example of such a system of farming withoutmanure is to be found in the alluvial soils of the United Provinces inIndia where the field records of ten centuries prove that the landproduces small crops year after year without any falling off infertility. A perfect balance has been reached between the manurialrequirements of the crops harvested and the natural processes whichrecuperate fertility. The greatest care, however, is taken not toover-cultivate, not to cultivate at the wrong time, or to stimulate thesoil processes by chemical manures. Systems of farming such as thesesupply as it were the base-line for agricultural development. A similarthough not so convincing result is provided by the permanent wheat plotat Rothamsted, where this crop has been grown on the same land withoutmanure since 1844. This plot, which has been without manure of any kindsince 1839, showed a slow decline in production for the first eighteenyears, after which the yield has been practically constant. The reservesof humus in this case left over from the days of mixed farming evidentlylasted for nearly twenty years. There are, however, two obviousweaknesses in this experiment. This plot does not represent any system ofagriculture, it only speaks for itself. Nothing has been done to preventearthworms and other animals from bringing in a constant supply ofmanure, in the shape of their wastes, from the surrounding land. It ismuch too small to yield a significant result.
Soil algae are a much more important factor in the tropics than intemperate regions. Nevertheless they occur in all soils and often play apart in the maintenance of soil fertility. Towards the end of the rainyseason in countries like India a thick algal film occurs on the surfaceof the soil which immobilizes a large amount of combined nitrogenotherwise likely to be lost by leaching. While this film is formingcultivation is suspended and weeds are allowed to grow. Just before thesowing of the cold weather crops in October the land is thoroughlycultivated, when this easily decomposable and finely divided organicmatter, which is rich in nitrogen, is transformed into humus and theninto nitrates. How far a similar method can be utilized in coldercountries is a matter for investigation. In the East cultivation alwaysfits in with the life-cycle in a remarkable way. In the West cultivationis regarded as an end in itself and not, as it should be, as a factor inthe wheel of life. Europe has much to learn from Asia in the cultivationof the soil.
TEMPORARY LEYS, CATCH-CROPS, GREEN-MANURES, AND THE TURF OF WORN-OUTGRASS LAND are perhaps the most important source of humus in Westernagriculture. All these crops develop a large root system; the permanentand temporary leys give rise to ample residues of organic matter whichaccumulate in the surface soil. Green-manures and catch-crops develop acertain amount of soft and easily decomposable tissue. Provided thesecrops are properly utilized a large addition of new humus can be added tothe soil. The efficiency of these methods of maintaining soil fertilitycould, however, be very greatly increased.
THE URINE OF ANIMALS. The key substance in the manufacture of humus fromvegetable wastes is urine--the drainage of the active cells and glands ofthe animal. It contains in a soluble and balanced form all the nitrogenand minerals, and in all probability the accessory growth-substances aswell, needed for the work of the fungi and bacteria which break down thevarious forms of cellulose--the first step in the synthesis of humus. Itcarries in all probability every raw material, known and unknown,discovered and undiscovered, needed in the building up of a fertile soil.Much of this vital substance for restoring soil fertility is eitherwasted or only imperfectly utilized. This fact alone would explain thedisintegration of the agriculture of the West.
Although FARM-YARD MANURE has always been one of the principal means ofreplenishing soil losses, even now the methods by which this substance isprepared are nothing short of deplorable. The making of farm-yard manureis the weakest link in the agriculture of Western countries. Forcenturies this weakness has been the fundamental fault of Westernfarming, one completely overlooked by many observers and the greatmajority of investigators.
DUSTBIN REFUSE. Practically no agricultural use is now being made of theimpure cellulose and kitchen wastes which find their way into the urbandustbin. These are mostly buried in controlled tips or burnt.
ANIMAL RESIDUES. A number of wastes connected with the processing of foodand some of the raw materials needed in industry are utilized on the landand find a ready market. The animal residues include such materials asdried blood, feathers, greaves, hair waste, hoof and horn, rabbit waste,slaughter-house refuse, and fish waste. There is a brisk demand for mostof these substances, as they give good results on the land. The onlydrawback is the limited supplies available. The organic residues frommanufacture consist of damaged oil-cakes, shoddy and tannery waste, ofwhich shoddy, a by-product of the wool industry, is the most important.These two classes of wastes, animal and industrial, are applied to thesoil direct and, generally speaking, command much higher prices thanwould be expected from their content of nitrogen, phosphorus, and potash.This is because the soil is in such urgent need of humus and because thesupply falls so far short of the demand. It is probable that a better usefor these wastes will be found as raw materials for the compost heaps ofthe future, where they will act as substitutes for urine in the breakingdown of dustbin refuse in localities where the supply of farm-yard manureis restricted.
WATER WEEDS. Little use is made of water weeds in maintaining soilfertility. Perhaps the most useful of these is seaweed, which is thrownup on the beaches in large quantities at certain times of the year andwhich contains iodine and includes the animal residues needed forconverting vegetable wastes into humus. Many of our sea-side resortscould easily manufacture from seaweed and dustbin refuse the vastquantities of humus needed for the farms and market gardens in theirneighbourhood and so balance the local agriculture. Little or nothing,however, is being done in this direction. In some cases the seaweedcollection on pleasure beaches is taken up by the farmers with goodresults, but the systematic utilization of seaweed in the compost heap isstill a matter for the future. The streams and rivers which carry off thesurplus rainfall also contain appreciable quantities of combined nitrogenand minerals in solution. Much of this could be intercepted by thecultivation of suitable plants on the borders of these streams whichwould furnish large quantities of easily decomposable material for humusmanufacture.
THE NIGHT SOIL AND URINE of the population is at present almostcompletely lost to the land. In urban areas the concentration of thepopulation is the main reason why water-borne sewage systems havedeveloped. The greatest difficulty in the path of the reformer is theabsence of sufficient land for dealing with these wastes. In countrydistricts, however, there are no insurmountable obstacles to theutilization of human wastes.
It will be evident that in almost every case the vegetable and animalresidues of Western agriculture are either being completely wasted orelse imperfectly utilized. A wide gap between the humus used up in cropproduction and the humus added as manure has naturally developed. Thishas been filled by chemical manures. The principle followed, based on theLiebig tradition, is that any deficiencies in the soil solution can bemade up by the addition of suitable chemicals. This is based on acomplete misconception of plant nutrition. It is superficial andfundamentally unsound. It takes no account of the life of the soil,including the mycorrhizal association--the living fungous bridge whichconnects soil and sap. Artificial manures lead inevitably to artificialnutrition, artificial food, artificial animals, and finally to artificialmen and women.
The ease with which crops can be grown with chemicals has made thecorrect utilization of wastes much more difficult. If a cheap substitutefor humus exists why not use it? The answer is twofold. In the firstplace, chemicals can never be a substitute for humus because Nature hasordained that the soil must live and the mycorrhizal association must bean essential link in plant nutrition. In the second place, the use ofsuch a substitute cannot be cheap because soil fertility--one of the mostimportant assets of any country--is lost; because artificial plants,artificial animals, and artificial men are unhealthy and can only beprotected from the parasites, whose duty it is to remove them, by meansof poison sprays, vaccines and serums and an expensive system of patentmedicines, panel doctors, hospitals, and so forth. When the finance ofcrop production is considered together with that of the various socialservices which are needed to repair the consequences of an unsoundagriculture, and when it is borne in mind that our greatest possession isa healthy, virile population, the cheapness of artificial manuresdisappears altogether. In the years to come chemical manures will beconsidered as one of the greatest follies of the industrial epoch. Theteachings of the agricultural economists of this period will be dismissedas superficial.
In the next section of this book the methods by which the agriculture ofthe West can be reformed and balanced and the use of artificial manuresgiven up will be discussed.
CLARKE, G. 'Some Aspects of Soil Improvement in relation to CropProduction' Proc. of the Seventeenth Indian Science Congress,Asiatic Society of Bengal, Calcutta, 1930, p. 23
HALL, SIR A. DANIEL. The Improvement of Native Agriculture in relation toPopulation and Public Health, Oxford University Press, 1936.
HOWARD, A., and WAD, Y. D. The Waste Products of Agriculture:Their Utilization as Humus, Oxford University Press, 1931
MANN, H. H., JOSHI, N. V., and KANITICAR, N. V. 'The Rab System of RiceCultivation in Western India', Mem. of the Dept. of Agriculture in India(Chemical Series), ii 1912, p. 141.
Manures and Manuring, Bulletin 36 of the Ministry of Agricultureand Fisheries, H.M. Stationery Office, 1937.
PART II THE INDORE PROCESS
THE INDORE PROCESS
The Indore Process for the manufacture of humus from vegetable and animalwastes was devised at the Institute of Plant Industry, Indore, CentralIndia, between the years 1924 and 1931. It was named after the IndianState in which it originated, in grateful remembrance of all the IndoreDarbar did to make my task in Central India easier and more pleasant.
Although the working out of the actual process only took seven years, thefoundations on which it is based occupied me for more than a quarter of acentury. Two independent lines of thought and study led up to the finalresult. One of these concerns the nature of disease and is discussed morefully in Chapter XI under the heading--'The Retreat of the Crop and theAnimal before the Parasite'. It was observed in the course of thesestudies that the maintenance of soil fertility is the real basis ofhealth and of resistance to disease. The various parasites were found tobe only secondary matters: their activities resulted from the breakdownof a complex biological system--the soil in its relation to the plant andto the animal--due to improper methods of agriculture, an impoverishedsoil, or to a combination of both.
The second line of thought arose in the course of nineteen years(1905-24) spent in plant-breeding at Pusa, when it was gradually realizedthat the full possibilities of the improvement of the variety can only beachieved when the soil in which the new types are grown is provided withan adequate supply of humus. Improved varieties by themselves could berelied upon to give an increased yield in the neighbourhood of 10 percent.: improved varieties plus better soil conditions were found toproduce an increment up to 100 per cent. or even more. As an addition ofeven 10 per cent. to the yield would ultimately impose a severe strain onthe frail fertility reserves of the soils of India and would graduallylead to their impoverishment, plant-breeding to achieve any permanentsuccess would have to include a continuous addition to the humus contentof the small fields of the Indian cultivators. The real problem was notthe improvement of the variety but how simultaneously to make the varietyand the soil more efficient.
By about the year 1918 these two hitherto independent approaches to theproblems of crop production--by way of pathology and by way ofplant-breeding--began to coalesce. It became clearer and clearer thatagricultural research itself was involved in the problem; that theorganization was responsible for the failure to recognize the things thatmatter in agriculture and would therefore have to be reformed; theseparation of work on crops into such compartments as plant-breeding,mycology, entomology, and so forth, would have to be given up; the plantwould have to be studied in relation to the soil on the one hand and tothe agricultural practices of the locality on the other. An approach tothe problems of crop production on such a wide front was obviouslyimpossible in a research institute like Pusa in which the work on cropswas divided into no less than six separate sections. The working out of amethod of manufacturing humus from waste products and a study of thereaction of the crop to improved soil conditions would encroach on thework of practically every section of the Institute. As no progress hasever been made in science without complete freedom, the only way ofstudying soil fertility as one subject appeared to be to found a newinstitute in which the plant would be the centre of the subject and wherescience and practice could be brought to bear on the problem without anyconsideration of the existing organization of agricultural research.Thanks to the support of a group of Central Indian States and a largegrant from the Indian Central Cotton Committee, the Institute of PlantIndustry was founded at Indore in 1924. Central India was selected as thehome of this new research centre for two reasons: (1) the offer on a 99years' lease of an area of 300 acres of suitable land by the IndoreDarbar, and (2) the absence in the Central India Agency of any organizedsystem of agricultural research such as had been established throughoutBritish India. This tract therefore provided the land on the one hand andfreedom from interference on the other for the working out of a newapproach, based on the humus content of the soil, to the problemsunderlying crop production. (An account of the organization of theInstitute of Plant Industry was published as THE APPLICATION OF SCIENCETO CROP-PRODUCTION by the Oxford University Press in 1929.)
The work at Indore accomplished two things: (1) the obsolete character ofthe present-day organization of agricultural research was demonstrated;(2) a practical method of manufacturing humus was devised.
The Indore Process was first described in detail in 1931 in Chapter IV ofTHE WASTE PRODUCTS OF AGRICULTURE. Since that date the method has beentaken up by most of the plantation industries and also on many farms andgardens all over the world. In the course of this work nothing has beenadded to the two main principles underlying the process, namely, (1) theadmixture of vegetable and animal wastes with a base for neutralizingacidity, and (2) the management of the mass so that the micro-organismswhich do the work can function in the most effective manner. A number ofminor changes in working have, however, been suggested. Some of thesehave proved advantageous in increasing the output. In the followingaccount the original description has been followed, but all usefulimprovements have been incorporated: the technique has been brought up todate.
THE RAW MATERIALS NEEDED
1. VEGETABLE WASTES. In temperate countries like Great Britain theseinclude--straw, chaff, damaged hay and clover, hedge and bank trimmings,weeds including sea-and water-weeds, prunings, hop-vine and hop-string,potato haulm, market-garden residues including those of the greenhouse,bracken, fallen leaves, sawdust, and wood shavings. A limited amount ofother vegetable material like the husks of cotton seed, cacao, and groundnuts as well as banana stalks are also available near some of the largecities.
In the tropics and sub-tropics the vegetable wastes consist of verysimilar materials including the vegetation of waste areas, grass, plantsgrown for shade and green-manure, sugar-cane leaves and stumps, all cropresidues not consumed by live stock, cotton stalks, weeds, sawdust andwood shavings, and plants grown for providing compostable material on theborders of fields, roadsides, and any vacant corners available.
A continuous supply of mixed dry vegetable wastes throughout the year, ina proper state of division, is the chief factor in the process. The idealchemical composition of these materials should be such that, after beingused as bedding for live stock, the carbon: nitrogen ratio is in theneighbourhood of 33:1. The material should also be in such a physicalcondition that the fungi and bacteria can obtain ready access to andbreak down the tissues without delay. The bark, which is the naturalprotection of the celluloses and lignins against the inroads of fungi,must first be destroyed. This is the reason why all woody materials--suchas cotton and pigeon-pea stalks--were always laid on the roads at Indoreand crushed by the traffic into a fine state of division beforecomposting.
All over the world one of the first objections to the adoption of theIndore Process is that there is nothing worth composting or only smallsupplies of such material. In practically all such cases any shortage ofwastes has soon been met by a more effective use of the land and byactually growing plants for composting on every possible square foot ofsoil. If Nature's way of using sunlight to the full in the virgin forestis compared with that on the average farm or on the average tea andrubber estate, it will be seen what leeway can be made up in growingsuitable material for making humus. Sometimes the objection is heard thatall this will cost too much. The answer is provided by the dust-bowls ofNorth America. The soil must have its manurial rights or farming dies.
2. ANIMAL RESIDUES. The animal residues ordinarily available all over theworld are much the same--the urine and dung of live stock, the droppingsof poultry, kitchen waste including bones. Where no live stock is keptand animal residues are not available, substitutes such as dried blood,slaughter-house refuse, powdered hoof and horn, fish manure, and so forthcan be employed. The waste products of the animal in some form or anotherare essential if real humus is to be made for the two following reasons.
(a) The verdict given by mother earth between humus made with animalresidues and humus made with chemical activators like calcium cyanamideand the various salts of ammonia has always been in favour of the former.One has only to feel and smell a handful of compost made by these twomethods to understand the plant's preference for humus made with animalresidues. The one is soft to the feel with the smell of rich woodlandearth: the other is often harsh to the touch with a sour odour. Sometimeswhen the two samples of humus made from similar vegetable wastes areanalysed, the better report is obtained by the compost made with chemicalactivators. When, however, they are applied to the soil the plantspeedily reverses the verdict of the laboratory. Dr. Rayner refers tothis conflict between mother earth and the analyst, in the case of somecomposts suitable for forestry nurseries, in the following words:
'Full chemical analyses are now available for a number of these composts,and it is not without interest to recall that in the initial stages ofthe work a competent critic reported on one of them--since proved to beamong the most effective a basis of comparative analysis, as "an organicmanure of comparatively little value"; while another--since proved leastsuccessful of all those tested--was approved as a "first-class organicmanure".'
The activator used in the first case was dried blood, in the second casean ammonium salt.
(b) No permanent or effective system of agriculture has ever been devisedwithout the animal. Many attempts have been made, but sooner or laterthey break down. The replacement of live stock by artificials is alwaysfollowed by disease the moment the original store of soil fertility isexhausted.
Where live stock is maintained the collection of their wasteproducts--urine and dung--in the most effective manner is important.
At Indore the work-cattle were kept in well-ventilated sheds with earthenfloors and were bedded down daily with mixed vegetable wastes includingabout 5 per cent. by volume of hard resistant material such as woodshavings and sawdust. The cattle slept on this bedding during the nightwhen it was still further broken up and impregnated with urine. Nextmorning the soiled bedding and cattle dung were removed to the pits forcomposting; the earthen floor was then swept clean and all wet placeswere covered with new earth, after scraping out the very wet patches. Inthis way all the urine of the animals was absorbed; all smell in thecattle sheds was avoided, and the breeding of flies in the earthunderneath the animals was entirely prevented. A new layer of bedding forthe next day was then laid.
Every three months the earth under the cattle was changed, theurine-impregnated soil was broken up in a mortar mill and stored undercover near the compost pits. This urine earth, mixed with any wood ashesavailable, served as a combined activator and base in composting.
In the tropics, where there is abundance of labour, no difficulty will beexperienced in copying the Indore plan. All the urine can be absorbed:all the soiled bedding can be used in the compost pits every morning.
In countries like Great Britain and North America, where labour is bothscarce and dear, objection will at once be raised to the Indore plan.Concrete or pitched floors are here the rule. The valuable urine and dungare often removed to the drains by a water spray. In such cases, however,the indispensable urine could either be absorbed on the floors themselvesby the addition to the bedding of substances like peat and sawdust mixedwith a little earth, or the urine could be directed into small brickedpits just outside the building, filled with any suitable absorbent whichis periodically removed and renewed. In this way liquid manure tanks canbe avoided. At all costs the urine must be used for composting.
3. BASES FOR NEUTRALIZING EXCESSIVE ACIDITY. In the manufacture of humusthe fermenting mixture soon becomes acid in reaction. This acidity mustbe neutralized, otherwise the work of the microorganisms cannot proceedat the requisite speed. A base is therefore necessary. Where thecarbonates of calcium or potassium are available in the form of powderedchalk or limestone, or wood ashes, these materials either alone,together, or mixed with earth, provide a convenient base for maintainingthe general reaction within the optimum range (pH 7.0 to 8.0) needed bythe microorganisms which break down cellulose. Where wood ashes,limestone, or chalk are not available, earth can be used by itself.Slaked lime can also be employed, but it is not so suitable as thecarbonate. Quicklime is much too fierce a base.
4. WATER AND AIR. Water is needed during the whole of the period duringwhich humus is being made. Abundant aeration is also essential during theearly stages. If too much water is used the aeration of the mass isimpeded, the fermentation stops and may soon become anaerobic too soon.If too little water is employed the activities of the micro-organismsslow down and then cease. The ideal condition is for the moisture contentof the mass to be maintained at about half saturation during the earlystages, as near as possible to the condition of a pressed-out sponge.Simple as all this sounds, it is by no means easy in practicesimultaneously to maintain the moisture content and the aeration of acompost heap so that the micro-organisms can carry out their workeffectively. The tendency almost everywhere is to get the mass toosodden.
The simplest and most effective method of providing water and oxygentogether is whenever possible to use the rainfall--which is a saturatedsolution of oxygen--and always to keep the fermenting mass open at thebeginning so that atmospheric air can enter and the carbon dioxideproduced can escape.
After the preliminary fungous stage is completed and the vegetable wasteshave broken down sufficiently to be dealt with by bacteria, the synthesisof humus proceeds under anaerobic conditions when no special measures forthe aeration of the dense mass are either possible or necessary.
PITS VERSUS HEAPS
Two methods of converting the above wastes into humus are in common use.Pits or heaps can be employed.
Where the fermenting mass is liable to dry out or to cool very rapidly,the manufacture should take place in shallow pits. A considerable savingof water then results. The temperature of the mass tends to remain highand uniform. Sometimes, however, composting in pits is disadvantageous onaccount of water-logging by storm water, by heavy rain, and by the riseof the ground-water from below. All these result in a wet sodden mass inwhich an adequate supply of air is out of the question. To obviate suchwater-logging the composting pits are: (1) surrounded by a catch-drain tocut off surface water; (2) protected by a thatched roof where therainfall is high and heavy bursts of monsoon rain are the rule; or (3)provided with soakaways at suitable points combined with a slight slopeof the floors of the pit towards the drainage corner. Where there is apronounced rise in the water-table during the rainy season, care must betaken, in siting the pits, that they are so placed that there is noinvasion of water from below.
To save the expense of digging pits and to use up sites where excavationis out of the question, composting in heaps is practiced. A great dealcan be done to increase the efficiency of the heap by protecting thecomposting area from storm water by means of catch-drains and by suitableshelter from wind, which often prevents all fermentation on the moreexposed sides of the heap. In temperate climates heaps should always facethe south, and wherever possible should be made in front of a south walland be protected from wind on the east and west. The effect of heavy rainin slowing down fermentation can be reduced by increasing the size of theheap as much as possible. Large heaps always do better than small ones.
In localities of high monsoon rainfall like Assam and Ceylon, there is adefinite tendency to provide the heap or the pit with a grass roof sothat the fermentation can proceed at an even rate and so that the annualoutput is not interfered with by temporary water-logging. After a year ortwo of service the roof itself is composted. In Great Britain thatchedhurdles can be used.
CHARGING THE HEAPS OR PITS
A convenient size for the compost pits (where the annual output is in theneighbourhood of 1,000 tons) is 30 feet by 14 feet and 3 feet deep withsloping sides. The depth is the most important dimension on account ofthe aeration factor. Air percolates the fermenting mass to a depth ofabout 18 to 24 inches only, so for a height of 36 inches extra aerationmust be provided. This is arranged by means of vertical vents, every 4feet, made by a light crowbar as each section of the pit is charged.
Charging a pit 30 feet long takes place in six sections each 5 feet wide.The first section, however, is left vacant to allow of the contents beingturned. The second section is first charged. A layer of vegetable wastesabout 6 inches deep is laid across the pit to a width of 5 feet. This isfollowed by a layer of soiled bedding or farm-yard manure 2 inches inthickness. The layer of manure is then well sprinkled with a mixture ofurine earth and wood ashes or with earth alone, care being taken not toadd more than a thin film of about one-eighth of an inch in thickness. Iftoo much is added aeration will be impeded. The sandwich is then wateredwhere necessary with a hose fitted with a rose for breaking up the spray.The charging and watering process is then continued as before until thetotal height of the section reaches 5 feet. Three vertical aerationvents, about 4 inches in diameter, are then made in the mass by working acrowbar from side to side. The first vent is in the centre, the other twomidway between the centre and the sides. As the pit is 14 feet wide andthere are three vents, these will be 3 feet 6 inches apart. The nextsection of the pit (5 feet wide) is then built up close to the first andwatered as before. When five sections are completed the pit is filled.The advantages of filling a pit or making a heap in sections to the fullheight of 5 feet are: (1) fermentation begins at once in each section andno time is lost; (2) no trampling of the mass takes place; (3) aerationvents can be made in each completed section without standing on themixture.
In dry climates each day's contribution to the pit should again belightly watered in the evening and the watering repeated the nextmorning. In this way the first watering at the time of charge is added inthree portions--one at the actual time of charging, in the evening aftercharging is completed and again the next morning after an interval oftwelve hours. The object of this procedure is to give the mass thenecessary time to absorb the water.
The total amount of water that should be added at the beginning offermentation depends on the nature of the material, on the climate and onthe rainfall. Watering as a rule is unnecessary in Great Britain. If thematerial contains about a quarter by volume of fresh greenstuff theamount of water needed can be considerably reduced. In rainy weather wheneverything is on the damp side no water at all is needed. Correctwatering is a matter of local circumstances and of individual judgement.At no period should the mass be wet: at no period should the pit beallowed to dry out completely. At the Iceni Nurseries in SouthLincolnshire in Great Britain, where the annual rainfall is about 24inches and a good deal of fresh green market-garden refuse is composted,watering the heaps at all stages is unnecessary. At Indore in CentralIndia where the rainfall was about 50 inches, which fell in about fourmonths, watering was always essential except during the actual rainyseason. These two examples prove that no general rule can ever be laiddown as to the amount of water to be added in composting. The amountdepends on circumstances. The water needed at Indore was from 200 to 300gallons for each cubic yard of finished humus.
As each section of the pit is completed, everything is ready for thedevelopment of an active fungous growth, the first stage in themanufacture of humus. It is essential to initiate this growth as quicklyas possible and then to maintain it. As a rule it is well established bythe second or third day after charging. Soon after the first appearanceof fungous growth the mass begins to shrink and in a few days will justfill the pit, the depth being reduced to about 36 inches.
Two things must be carefully watched for and prevented during the firstphase: (1) the establishment of anaerobic conditions caused generally byover-watering or by want of attention to the details of charging; it isat once indicated by smell and by the appearance of flies attempting tobreed in the mass; when this occurs the pit should be turned at once; (2)fermentation may slow down for want of water. In such cases the massshould be watered. Experience will soon teach what amount of water isneeded at the time of charge.
TURNING THE COMPOST
To ensure uniform mixture and decay and to provide the necessary amountof water and air for the completion of the aerobic phase it is necessaryto turn the material twice.
FIRST TURN. The first turn should take place between 2 and 3 weeks aftercharging. The vacant space, about 5 feet wide, at the end of the pitallows the mass to be conveniently turned from one end by means of apitchfork. The fermenting material is piled up loosely against the vacantend of the pit, care being taken to turn the unaltered layer in contactwith the air into the middle of the new heap. As the turning takes place,the mass is watered, if necessary, as at the time of charging, care beingtaken to make the material moist but not sodden with water. The aimshould be to provide the mass with sufficient moisture to carry on thefermentation to the second turn. To achieve this sufficient time must begiven for the absorption of water. The best way is to proceed as at thetime of charging and add any water needed in two stages--as the turningis being done and again next morning. Another series of vertical airvents 3 feet 6 inches apart should be made with a crowbar as the new heapis being made.
SECOND TURN. About five weeks after charge the material is turned asecond time but in the reverse direction. By this time the fungous stagewill be almost over, the mass will be darkening in colour and thematerial will be showing marked signs of breaking down. From now onwardsbacteria take an increasing share in humus manufacture and the processbecomes anaerobic. The second turn is a convenient opportunity forsupplying sufficient water for completing the fermentation. This shouldbe added during the actual turning and again the next morning to bringthe moisture content to the ideal condition--that of a pressed-outsponge. It will be observed as manufacture proceeds that the masscrumbles and that less and less difficulty occurs in keeping the materialmoist. This is due to two things: (1) less water is needed in thefermentation; (2) the absorptive and water-holding power of the massrapidly increase as the stage of finished humus is approached.
Soon after the second turn the ripening process begins. It is during thisperiod that the fixation of atmospheric nitrogen takes place. Underfavourable circumstances as much as 25 per cent. Of additional freenitrogen may be secured from the atmosphere.
The activity of the various micro-organisms which synthesize humus canmost easily be followed from the temperature records. A very hightemperature, about 65 degrees C. (149 degrees F.), is established at theoutset, which continues with a moderate downward gradient to 30 degreesC. (86 degrees F.) at the end of ninety days. This range fits in wellwith the optimum temperature conditions required for the micro-organismswhich break down cellulose. The aerobic thermophyllic bacteria thrive bestbetween 40 degrees C. (104 degrees F.) and 55 degrees C.(131 degrees F.). Before each turn, a definite slowing down in thefermentation takes place: this is accompanied by a fall in temperature.
As soon as the mass is re-made, when more thorough admixture with copiousaeration occurs, there is a renewal of activity during which theundecomposed portion of the vegetable matter from the outside of the heapor pit is attacked. This activity is followed by a distinct rise intemperature.
THE STORAGE OF HUMUS
Three months after charge the micro-organisms will have fulfilled theirtask and humus will have been completely synthesized. It is now ready forthe land. If kept in heaps after ripening is completed, a loss inefficiency must be faced. The oxidation processes will continue.Nitrification will begin, resulting in the formation of soluble nitrates.These may be lost either by leaching during heavy rain or they willfurnish the anaerobic organisms with just the material they need fortheir oxygen supply. Such losses do not occur to anything like the sameextent when the humus is banked by adding it to the soil. Freshlyprepared humus is perhaps the farmer's chief asset and must therefore belooked after as if it were actual money. It is also an important sectionof the live stock of the farm. Although this live stock can only be seenunder the microscope, it requires just as much thought and care as thepigs which can be seen with the naked eye. If humus must be stored itshould be kept under cover and turned from time to time.
The output of compost per annum obviously depends on circumstances. Atthe Institute of Plant Industry, Indore, where the supply of urine anddung was always greater than that of vegetable waste, fifty cartloads(each 27 c. ft.) of ripe compost, i.e. 1,350 cubic feet or 50 cubicyards, could be prepared from one pair of oxen. Had sufficient vegetablewastes been available the quantity could have been at least doubled. Thework-cattle at Indore were of the Malvi breed, about three-quarters thesize of the average milking-cow of countries like Great Britain. Theurine and dung of an average English cow or bullock, therefore, ifproperly composted with ample wastes would produce about sixty cartloadsof humus a year, equivalent to about 1,600 cubic feet or 60 cubic yards.
As the moisture content of humus varies from 30 to 60 per cent. duringthe year, it is impossible to record the output in tons unless thepercentage of water is determined. The difficulty can be overcome byexpressing the output in cubic feet or cubic yards. The rate ofapplication per acre should also be stated as so many cubic feet or cubicyards.
In devising the Indore Process the fullest use was made of agriculturalexperience including that of the past. After the methods of Nature, asseen in the forest, the practices which throw most light on thepreparation of humus are those of the Orient, which have been describedby King in FARMERS OF FORTY CENTURIES. In China a nation of observantpeasants has worked out for itself simple methods of returning to thesoil all the vegetable, animal, and human wastes that are available: adense population has been maintained without any falling off infertility.
Coming to the more purely laboratory investigations on the production ofhumus, two proved of great value in perfecting the Indore Process: (1)the papers of Waksman in which the supreme importance of micro-organismsin the formation of humus was consistently stressed, and (2) the work ofH. B. Hutchinson and E. H. Richards on artificial farm-yard manure.Waksman's insistence on the role of micro-organisms in the formation ofhumus as well as on the paramount importance of the correct compositionof the wastes to be converted has done much to lift the subject from amorass of chemical detail and empiricism on to the broad plane of biologyto which it rightly belongs. Once it was realized that compostingdepended on the work of fungi and bacteria, the reform of the variouscomposting systems which are to be found all over the world could betaken in hand. The essence of humus manufacture is first to provide theorganisms with the correct raw material and then to ensure that they havesuitable working conditions. Hutchinson and Richards come nearest to theIndore Process but two fatal mistakes were made: (1) the use of chemicalsinstead of urine as an activator in breaking down vegetable wastes, and(2) the patenting of the ADCO process. Urine consists of the drainage ofevery cell and every gland of the animal body and contains not only thenitrogen and minerals needed by the fungi and bacteria which break downcellulose, but all the accessory growth substances as well. The ADCOpowders merely supply factory-made chemicals as well as lime--a farinferior base to the wood ashes and soil used in the Indore Process. Itfocuses attention on yield rather than on quality. It introduces intocomposting the same fundamental mistake that is being made in farming,namely, the use of chemicals instead of natural manure. Further, thepatenting of a process (even when, as in this case, the patentees deriveno personal profit) always places the investigator in bondage; he becomesthe slave to his own scheme; rigidity takes the place of flexibility;progress then becomes difficult, or even impossible. The ADCO process waspatented in 1916: in 1940 the method to all intents and purposes remainsunchanged.
The test of any process for converting the waste products of agricultureinto humus is flexibility and adaptability to every possible set ofconditions. It should also develop and be capable of absorbing newknowledge and fresh points of view as they arise. Finally, it should besuggestive and indicate new and promising lines of research. If theIndore Process can pass these severe tests it will soon become woven intothe fabric of agricultural practice. It will then have achievedpermanence and will have furfilled its purpose--the restitution of theirmanurial rights to the soils of this planet. In the next four chaptersthe progress made during the last eight years towards this ideal will bedescribed.
HOWARD, A., and HOWARD, G. L. C. The Application of Science toCrop-Production, Oxford University Press, 1929.
HOWARD, A., and WAD, Y. D. The Waste Products of Agriculture:Their Utilization as Humus, Oxford University Press, 1931.
PRACTICAL APPLICATIONS OF THE INDORE PROCESS
After the first complete account of the Indore Process was published in1931, the adoption of the method at a number of centres followed veryquickly. The first results were summarized in a lecture which appeared inthe issue of the Journal of the Royal Society of Arts of December 8th,1933. About 2,000 extra copies of this lecture were printed anddistributed during the next two years. By the end of 1935 it becameevident that the method was making very rapid headway all over the world:an increasing stream of interesting results were reported. These weredescribed in a second lecture on November 13th, 1935, which was printedin the Journal of the Society of November 22nd, 1935. This lecture wasthen re-published in pamphlet form. In all 6,425 extra copies of thissecond lecture have been distributed. During 1936 still further progresswas made, a brief account of which appeared in the Journal of the RoyalSociety of Arts of December 18th, 1936; 7,500 copies being printed. Twotranslations of the 1935 lecture have been published. The first in Germanin Der Iropenpflanzer of February 1936, the second in Spanish in theRevista del Instituto de Defensa del Cafe de Costa Rica of March 1937.
These papers did much to make the Indore Process known all over the worldand to start a number of new and active composting centres. The position,as reached by July 1938, was briefly sketched in a paper which waspublished in the Journal of the Ministry of Agriculture of Great Britainof August 1938.
In this and succeeding chapters an attempt will be made to sum upprogress to the time of going to press. It will be convenient in thefirst place to arrange this information under crops.
The first centre in Africa to take up the process was the KingatoriEstate near Kyambu, a few miles from Nairobi, where work began inFebruary 1933. By the purest accident I saw the first beginnings ofcomposting at this estate. This occurred in the course of a tour roundAfrica which included a visit to the Great Rift Valley. As I was about tostart from Nairobi on this expedition, Major Belcher, the Manager ofKingatori, called upon me and said that he had just been instructed byMajor Grogan, the proprietor of the Estate, to start the Indore Processand to convert all possible wastes into humus. He asked me to help himand to discuss various practical details on the spot. I gave up the tourto the Great Rift Valley and spent the day on the Kingatori Estateinstead, where it was obvious from the general condition of the bushesand the texture of the soil that a continuous supply of freshly madehumus would transforn this estate, which I was told was representative ofthe coffee industry near Nairobi. In a letter dated September 19th, 1933,Major Belcher reported his first results as follows:
'I have 30 pits in regular use now, and am averaging 5 tons of ripecompost from each pit. This will give me a dressing of 3-1/2 tons peracre per annum and should, I think, gradually bring the soil into reallygood condition.
'I have already dressed 30 acres, but it is a little early to see anyresult. It is 30 acres of young 4-year old coffee bearing a heavy crop.At the moment it is looking splendid, and if it keeps it up until thecrop is picked in December and enables the trees to bear heavily againnext year there will be no doubt in my mind that the compost isresponsible. Young trees with a big crop are very apt to suffer fromdie-back of the primaries and light beans and no crop in the followingyear. There is no sign of this at present.
'I have had many interested visitors, and the Nairobi bookseller has tokeep sending for more copies of The Waste Products of Agriculture.
'The District Commissioner at Embu has taken up the process extensivelywith the double purpose of improving village sanitation and the fertilityof the soil. In fact, he started it some time before we did.
'I understand that it will shortly be made illegal to export goat andcattle manure from the native reserves, in which case your process willbe taken up by most of the European farmers in the Colony. One veryinfluential member of the coffee industry remarked to me that he thoughtyour process would revolutionize coffee-growing and another said that heconsidered it was the biggest step forward made in the last ten years.'
Two years later he sent me a second report in which he stated that duringthe last 28 months 1,660 tons of compost, containing, about 1.5 per cent.of nitrogen, had been manufactured on this estate and applied to theland. The cost per ton was 4s. 4d.--chiefly the expense involved incollecting raw material. The work in progress had been shown to aconstant stream of visitors from other parts of Kenya, the Rhodesias,Uganda, Tanganyika, and the Belgian Congo. Major Belcher has lost countof the actual numbers.
This pioneering work has done much more than weld the Indore Process intothe routine work of the estate. It has served the purpose of anexperiment station and a demonstration area for the coffee industrythroughout the world. Many new centres followed Kingatori. The rapidspread of the method is summed up by Major Grogan in a letter datedNairobi, May 15th, 1935, as follows:
'You will be glad to know that your process is spreading rapidly in theseparts and has now become recognized routine practice on most of the wellconducted coffee plantations. The cumulative effect of two years on myplantation is wonderful. I have now established all round my pits a largearea of elephant grass for the purpose of providing bulk, and we havemade quite a lot of pocket-money by selling elephant grass cuttings tothe country-side. I am now searching for the best indigenous legumes togrow in conjunction with the elephant grass and am getting very hopefulresults from the various Crotaleries and Tephrosies which I have broughtup from the desert areas of Taveta. They get away quickly and so holdtheir own against the local weeds.'
Major Grogan in referring to the spread of the Indore Process in EastAfrica, has omitted one very material factor, namely, his personal sharein this result. He initiated the earliest trial on the Kingatori Estateand has always insisted on the method having a square deal in Kenya. InTanganyika the influence of Sir Milsom Rees, G.C.V.O., has led to similarresults.
This example of the introduction and spread of the Indore Process on thecoffee estates of Kenya and Tanganyika has been given in detail for threereasons: (1) it was one of the earliest applications of the Indore methodto the plantation industries; (2) it is typical of many other similarapplications elsewhere; and (3) it first suggested to me a new field ofwork during retirement in which the research experience of a lifetimecould be fully utilized.
Kenya and Tanganyika are only two of the coffee centres of the world. Thelargest producer is the New World. Here satisfactory progress has beenmade following the publication in the West India Committee Circular ofApril 23rd, 1936, of a short account of the Indore Process. This led toimportant developments, first in Costa Rica and then in Central and SouthAmerica, as a result of a Spanish translation by Senor Don MarianoMontealegre of my 1935 lecture to the Royal Society of Arts to whichreference has already been made. This was widely read in all parts ofLatin America: the lecture drew attention to the vital necessity oforganic matter in the production of coffee in the New World. During thenext two years no less than seven Spanish translations of my papers onhumus were published in the Revista del Instituto de Defensa del Cafe deCosta Rica. In January 1939 a special issue of the Revista entitled EnBusca del Humus (In Quest of Humus) appeared. This was devoted to acollection of papers describing the Indore Process and the variousdevelopments of the last eight years.
The marked response of coffee to humus in Africa, India, and the NewWorld suggested that the crop would prove to be a mycorrhiza-former. Anumber of samples of the surface roots of coffee plants were dulycollected in Travancore, Tanganyika, and Costa Rica and sent home forexamination. In all cases they showed the mycorrhizal association.
The East African results with coffee naturally suggested that somethingshould be done with regard to tea--a highly organized plantation industrywith the majority of the estates arranged in large groups, controlled bya small London Directorate largely recruited from the industry itself.The problem was how best to approach such an organization. In 1934 myknowledge of tea and of the tea industry was of the slightest: I hadnever grown a tea plant, let alone managed a tea plantation. I had onlyvisited two tea estates, one near Nuwara Eliya in Ceylon in 1908 and theother near Dehra Dun in 1918. I had, however, kept in touch with theresearch work on tea. While I was debating this question Providence cameto my assistance in the shape of a request from a mutual friend to helpDr. C. R. Harler (who had just been retrenched when the Tocklai ResearchStation, maintained by the Indian Tea Association, was reorganized in1933) to find a new and better opening, if possible one with more scopefor independent and original work. I renewed my acquaintance with Dr.Harler and suggested he should take up the conversion into humus of thewaste products of tea estates. He was very interested and shortlyafterwards (August 1933) accepted the post of Scientific Officer to theKanan Devan Hills Produce Co. in the High Range, Tray encore, which wasoffered him by Messrs. James Finlay & Co., Ltd. On taking up his duties inthis well-managed and highly efficient undertaking, Dr. Harler securedthe active interest of the then General Manager, Mr. T. Wallace, and setto work to try out the Indore Process on an estate scale at hishead-quarters at Nullatanni, near Munnar. No difficulties were met within working the method: ample supplies of vegetable wastes and cattlemanure were available: the local labour took to the work and the EstateManagers soon became enthusiastic.
On receipt of this information I made inquiries from Dr. H. H. Mann, aformer Chief Scientific Officer of the Indian Tea Association, as towhether the live wires among the London Directorate of the tea industryincluded anybody likely to be particularly interested in the humusquestion.
I was advised to see Mr. James Insch, one of the Managing Directors ofMessrs. Walter Duncan & Co. At Mr. Insch's request an illustrated paperof instructions for the use of the Managers of the Duncan Group was drawnup in October 1934 and 250 copies were printed. The Directors of othergroups of tea estates soon began to consider the Indore Process and 4,000further copies of the paper of instructions were distributed. By the endof 1934 fifty-three estates of the Duncan Group in Sylhet, Cachar, theAssam Valley, the Dooars, Terai, and the Darjeeling District had made anddistributed sample lots of humus, about 2,000 tons in all. At the time ofwriting, December 1939, the estates of the Duncan Group alone expect tomake over 150,000 tons of humus a year. Similar developments haveoccurred in a number of other groups notably on the estates controlled byMessrs. James Finlay & Co., who have never lost the lead in manufacturinghumus which naturally followed from the pioneering work done by Dr.Harler in Travancore. A good beginning has been made. The two strongestgroups of tea estates in the East have become compost-minded.
It is exceedingly difficult to say exactly how much humus is being madeat the present time on the tea estates of the British Empire. It ispossible only to give a very approximate figure. In April 1938 Messrs.Masefield and Insch stated: 'It is probably no exaggeration to say thatto-day a million tons of compost are being made annually on the teaestates of India and Ceylon, and this has been accomplished within aperiod of 5 years.' Since this was written the tea estates of Nyasalandand Kenya have also taken up the Indore Process with marked success.
These developments have been accompanied by a considerable amount ofdiscussion. Two views have been and are still being held on the best wayof manuring tea. One school of thought, which includes the tea researchinstitutes, considers that as the yield of leaf is directly influenced bythe supply of combined nitrogen in the soil, the problem of soilfertility is so simple as to reduce itself to the use of the cheapestform of artificial manure--in this case sulphate of ammonia. This view isnaturally vigorously supported by the artificial manure interests. Theresults obtained with sulphate of ammonia on small plots at Tocklai andBorbhetta are triumphantly brought forward to clinch the argument whichamounts to this: that tea can be grown on a conveyor-belt lubricated bychemical fertilizers. The weaknesses of such an argument are obvious.These small plots do not represent anything in the tea industry: theyonly represent themselves. It is impossible to run a small plot or tomanufacture and sell its produce as a teagarden is conducted. In otherwords the small plot is not practical politics. Again, land like Tocklaiand Borbhetta which responds so markedly to sulphate of ammonia must bebadly farmed, otherwise artificials would not prove so potent. Thetendency all the world over is that as the soil becomes more fertileartificials produce less and less result until the effect passes offaltogether. Bad farming and an experimental technique which will not holdwater are poor foundations on which to found a policy. The use ofreplicated and randomized plots, followed by the higher mathematics ininterpreting the results of these small patches of land, can do nothingto repair the fundamental unsoundness of the Tocklai procedure. It standsself-condemned. Further, the advocates of sulphate of ammonia for the teaplant seem to have forgotten that a part at least of the extra yieldobtained with this manure may be due to an increase in soil acidity. Tea,as is well known, needs an acid soil: sulphate of ammonia increasesacidity.
The humus school of thought takes the view that what matters in tea isquality and a reserve of soil fertility such as that created by theprimeval forest: that this can only be obtained by freshly prepared humusmade from vegetable and animal wastes and by the correct use of shadetrees, green-manure crops, and the prevention of soil erosion. The momentthe tea soils can be made really fertile, the supply of nitrogen to theplant will take care of itself and there will be no need to waste moneyin securing the fleeting benefits conferred by artificials. The problemtherefore of the manuring of tea is not so much the effect of somedressing on the year's yield but the building up of a store of fertility.In this way the manurial problem and the stability of the enterprise as agoing concern become merged into one. It is impossible to separate theprofit and loss account and the balance-sheet of a composting programmebecause the annual dressings of humus influence both.
It will be interesting to watch the results of this struggle in a greatplantation industry. At the moment a few of the strongest and mostsuccessful groups are taking up humus and spend little or nothing onartificials. Other companies, on the other hand, are equally convincedthat their salvation lies in the use of cheap chemical fertilizers.Between these two extremes a middle course is being followed--humussupplemented by artificials. Mother earth, rather than the advocates ofthese various views, will in due course deliver her verdict.
Can the tea plant itself throw any light on this controversy or is itcondemned to play a merely passive role in such a contest? Has the teabush anything to say about its own preference? If it has, itsrepresentations must at the very least be carefully considered. The plantor the animal will answer most queries about its needs if the question isproperly posed and if its response is carefully studied.
During the early trials of the Indore Process it became apparent that thetea plant had something very interesting to communicate on the humusquestion. Example after example came to my notice where such smallapplications of compost as five tons to the acre were at once followed bya marked improvement in growth, in general vigour and in resistance todisease. Although very gratifying, in one sense these results weresomewhat disconcerting. If humus acts only indirectly by increasing thefertility of the soil, time will be needed for the various physical,biological, and chemical changes to take place. If the plant responds atonce, some other factor besides an improvement in fertility must be atwork. What could this factor be?
In a circular letter issued on October 7th, 1937, to correspondents inthe tea industry, I suggested that the most obvious explanation of anysudden improvement in tea, observed after one application of compost, isthe effect of humus in stimulating the mycorrhizal relationship which isknown to occur in the roots of this crop.
In the course of a recent tour (November 1937 to February 1938) to teaestates in the East, I examined the root system of a number of tea plantswhich had been manured with properly made compost, and found everywherethe same thing--numerous tufts of healthy-looking roots associated withrapidly developing foliage and twigs much above the average. Both belowand above ground humus was clearly leading to a marked condition ofwell-being. When the characteristic tufts of young roots were examinedmicroscopically, the cortical cells were seen to be literally overrunwith mycelium and to a much greater extent than is the rule in a reallyserious infection by a parasitic fungus. Clearly the mycorrhizalrelationship was involved. These necessarily hasty and imperfectobservations, made in the field, were. soon confirmed and extended by Dr.M. G Rayner and Dr. Ida Levisohn, who examined a large number of mysamples including a few in which artificials only were used, or where thesoils were completely exhausted and the garden had become derelict withperhaps only half the full complement of plants. In these cases thecharacteristic tufts of healthy roots were not observed; root developmentand growth were both defective; the mycorrhizal relationship was eitherabsent or poorly developed. Where artificials were used on worn-out tea,infection by brownish hyphae of a Rhizoctonia-like fungus (oftenassociated with mild parasitism) was noticed. Whenever the roots of tea,manured with properly made compost, were critically examined, the wholeof the cortical tissues of the young roots always showed abundantendotrophic mycorrhizal infection, the mainly intracellular myceliumapparently belonging to one fungus. The fungus was always confined to theyoung roots and no extension of the infection to old roots was observed.In the invaded cells the mycelium exhibits a regular cycle of changesfrom invasion to the clumping of the hyphae around the cell nuclei,digestion and disintegration of their granular contents, and the finaldisappearance of the products from the cells.
Humus in the soil therefore affects the tea plant direct by means of amiddleman--the mycorrhizal relationship. Nature has provided aninteresting piece of living machinery for joining up a fertile soil withthe plant. Obviously we must pay the closest attention to theresponse--as regards yield, quality, and disease resistance--whichfollows the use of this wonderful bit of mechanism. We must also see thatthe humus content of the soil is such that the plant can make the fullestpossible use of its own machinery.
The mycorrhizal relationship in tea and its obvious bearing on thenutrition of the plant places the manurial problems of this crop on a newplane--that of applied biology. The well-being of the tea plant does notdepend on the cheapest form of nitrogen but on humus and the consequencesof the mycorrhizal relationship. We are obviously dealing with a forestplant which thrives best on living humus--not on the dead by-product of afactory.
It is easy to test the correctness of this view. It can be done in twoways: (1) by a comparison of tea seedlings grown on sub-soil (from whichthe surface soil containing humus has been removed) and manured eitherwith a complete artificial mixture or with freshly prepared humus, and(2) by observing the effect of artificials on a tea-garden where the soilis really fertile. Such trials have already been started. In the case ofseedlings grown on subsoil manured with: (1) no tons of humus to theacre, or (2) the equivalent amount of NPK in the form of artificials, Mr.Kenneth Morford has obtained some very interesting results at MountVernon in Ceylon. Nine months after sowing, the humus plot was by far thebetter--the plants were 10 high, branched, with abundant, healthy, darkgreen foliage. The plots with artificials were 6 inches high, unbranched,with sparse, unhealthy, pale foliage. An examination of the root systemswas illuminating. The humus plants developed a strong tap root 12 incheslong; the artificials plot showed little attempt to develop any tap rootat all, only extensive feeding roots near the surface. The root system atonce explained why the humus plot resisted drought and why the artificialmanure plot was so dependent on watering. Mr. Morford's experiment shouldbe repeated in some of the other tea areas of the East. The results willspeak for themselves and will need no argument.
The effect of sulphate of ammonia on a really fertile soil is mostinteresting. As would be expected the results have been for the most partalmost negative, because there is no limiting factor in the shape of adeficiency of nitrogen, phosphorus, or potash under such conditions. Onold estates, where organic matter has not been regularly replaced,resulting in the loss of much of the original fertility, such anexperiment would give a clear indication as to whether, under existingmanagement, the soil is losing, maintaining, or gaining in fertility.Given an adequate supply of humus in the soil, the mycorrhizalrelationship and the nitrification of organic matter, when allowed towork at top speed, are all that the plant needs to produce a full crop ofthe highest quality possible under local conditions. The tea planttherefore is already preparing its own evidence in the suit--Humus versusSulphate of Ammonia.
The problem of the manuring of tea is straightforward. It consists inconverting the mixed vegetable wastes of a tea estate and of thesurrounding land into humus by means of the urine and dung of an adequateherd of live stock--cattle, pigs, or goats. As the tea districts aresituated in regions of high rainfall it will be necessary in many casesto protect the heaps or pits from heavy rain. Ample vegetable waste mustalso be provided. The solution of the practical problems involved willnecessarily depend on local conditions. At Gandrapara in the Dooars, anestate influenced by the south-west monsoon, Mr. J. C. Watson has setabout the provision of an ample supply of humus in a very thorough-goingmanner, an account of which will be found in Appendix A. It cannot failto interest not only the producers of tea but the whole of the plantationindustries as well.
The conversion of vegetable and animal wastes into humus is only oneaspect of the soil-fertility problem of a tea-garden. There are a numberof others such as the use of shade trees, drainage, prevention oferosion, the best manner of utilizing tea prunings and green-manure, theutilization of water-weeds like the water hyacinth, the treatment of rootdisease, the raising of seed, the manufacture of humus from vegetablewastes only, and the effect of artificial manures on the quality of tea.These will now be briefly discussed.
Generally speaking, more attention is paid to shade trees in North-EastIndia than in South India and Ceylon. There is a tendency for shade todecrease as one proceeds south. It may be that the factor which hasdetermined the invariable use of shade in North-East India is theintense dryness and heat of the period March to June which does not occurin the south. As, however, tea is a forest plant and tea-growing mustalways be looked upon as applied forestry, it would seem to be a mistaketo reduce shade too much. The organic matter provided by the roots andleaves of the shade trees, the protection they afford the soil from thesun, wind, and rain, and the well-known advantage of mixed cropping mustall be very important factors in the maintenance of fertility. This isborne out by the superior appearance of the tea on well-shaded estates inCeylon compared with that on land alongside where the shade trees havebeen removed.
A large amount of the vegetable wastes on a tea estate consists ofprunings and green-manure plants. These are either forked in, buried inlong shallow trenches, or made into humus. Is there any more effectivemethod of dealing with these wastes? When the tea is pruned the plantmakes a new bush. Could it not be induced to re-make a portion of itsroot system at the same time in well-aerated rich soil? I think it could.On estates provided with adequate shade and contour drains, the followingtwo methods of composting tea prunings and green-manure might be triedout:
1. This material should be forked in with a dressing of compost at therate of 5 to 10 tons an acre. Decay will then be much more rapid andeffective than is now the case. This method of the sheet composting oftea prunings has been tried out and found successful at Gandrapara.
2. The prunings and green-manure should be composted in small pitsbetween alternate rows of tea. The pits should be 2 feet long and 1-1/2feet wide and 9 inches to a foot deep, parallel to the drains or contourdrains and so arranged that the roots of every tea plant come in contactwith one pit only. The pits are then nearly half filled with mixed teaand green-manure prunings, which are then covered with a thin layer ofcompost or cattle manure. More green material is added until the pit isnearly full. It is then covered with three inches of soil. The pits nowbecome small composting chambers; humus is produced while the tea is notgrowing a crop; earthworms are encouraged; the roots of the neighbouringtea plants soon invade the pit; a portion of the root system of all thetea plants of the area is then re-created in highly fertile, permeablesoil. When the pruned bushes need tipping on estates where the firstpicking is not manufactured, another set of similar pits can be made inthe vacant spaces between the first pits in each line and similarlyfilled.
When next the bushes are pruned exactly the same procedure can be carriedout in the hitherto undisturbed spaces between the rows of tea.
When the fourth set of pits has been made each tea bush will havecompleted the re-creation of a large portion of its root system in richearth.
The first large-scale trial of the pit method was begun at Mount Vernonin Ceylon in January 1938. The results have been satisfactory in allrespects. the yield of tea has increased: the plants have resisteddrought: the cost of the work has proved to be a sound investment.
On several tea estates in Assam the low-lying areas among the tea areused for the growth of water hyacinth for the compost heaps. When thismaterial forms a quarter to a third of the volume of the heap, wateringduring the dry season can be reduced very considerably. Aboutthree-quarters of the weed is harvested, the remainder being left toproduce the next year's crop. As water hyacinth is known to diminish thenumber of mosquitoes it might pay a tea estate from the point of view ofmalaria control only to grow this plant for composting on all low-lyingareas. When water hyacinth becomes widely cultivated on the tea estatesfor humus manufacture, the labour employed will undoubtedly carry thenews to the great rice areas of Northeast India. Here one of the greatestadvances in food production in the world can be achieved by theconversion of water hyacinth first into humus and then into rice.
In many of the tracts which produce tea small areas occur in which thebushes are attacked by root disease. It is probable that local soil pans,some distance below the surface, are holding up the drainage and thatthis stagnant water lowers the natural resistance of the tea plant. Isuggested in the Report on my tour that vertical pillar drains, filledwith stones, pebbles, or even surface soil, might prevent these troubles.Similar drains are used in Sweden with good results.
The weakest link in the tea industry is the production of seed. Duringthe whole of my tour I saw few really well-managed seed gardens. It isessential that the trees which bear seed should be properly selected,adequately spaced, well drained, and manured with freshly preparedcompost. Nature will provide an automatic method of seed control. Ifdiseases appear on the trees or in the seeds something is wrong. Only ifthe trees and seed are healthy, vigorous, and free from pests, is theproduce of such trees fit for raising plants, which in China are said tolast a hundred years. The tea plant must have a good start in life.
In Ceylon particularly, attempts have been made to prepare humus withoutanimal wastes. The results have not furfilled expectation. The breakingdown of such resistant material as the leaves and prunings of tea is thenunsatisfactory: the organisms which synthesize humus are not properlyfed: the residues of these organisms which form an important part of thefinal humus lack the contributions of the animal. No one has yetsucceeded in establishing an efficient and permanent system ofagriculture without live stock. There is no reason therefore to supposethat the tea industry will prove an exception to what, after all, is arule in Nature.
One of the most discussed topics in tea is the effect of artificialmanures on quality. The view is widely held that there has been a gradualloss in quality since chemical manures were introduced. One of theplanters in the Darjeeling District, Mr. G. W. O'Brien, the proprietor ofthe Goomtee and Jungpana Tea Estates, who continues to produce tea of thehighest quality, informed me in 1935 that he had never used artificialssince the estates came under his management thirty-one years ago. Theonly manure used is cattle manure and vegetable wastes--in other words,humus. The role of the mycorrhizal relationship in tea helps to provide ascientific explanation of these results. There can be little doubt thatthis relationship will be found to influence the quality of tea as wellas the productivity and health of the bush. Humus and the mycorrhizalrelationship cannot of course create quality where it never existed: theutmost these factors can achieve is to restore that degree of qualitywhich any locality possessed when first it was brought from forest undertea.
The waste products of the sugar-cane vary considerably. In peasantagriculture where the whole of the megass is burnt for evaporating thejuice in open pans, the chief waste is old cane leaves, cane stumps, andthe ashes left by the fuel. On the sugar estates, a number of factorywastes must be added to the above list--filter press cake, some unburntmegass, and the distillery effluent left after the manufacture of alcohol(known in Natal as dunder). The main waste in both cases, however, is theold dead leaves (cane trash), a very difficult material to turn intohumus on account of its structure and its chemical composition.
Before the advent of artificial fertilizers, it was the custom on sugarestates to maintain animals---mules and oxen--for transport and forcultivation. These animals were bedded down with cane trash, and a roughfarm-yard manure--known in the West Indies as pen manure--was obtainedwith the help of their wastes. Soon after the introduction of artificialmanures, the value of this product began to be assessed on the basis ofchemical analysis. Comparisons were made between the cost of productionof its content of NPK and that of an equivalent amount of these chemicalelements in the form of artificial manure. The result was chemicals soonbegan to displace pen manure: the animal came to be regarded as anexpensive luxury. The advent of the tractor and the motor-lorry settledthe question. Why keep expensive animals like mules and oxen which haveto be fed from the land when their work can be done more cheaply bymachines and imported fuel? The decision to give up animals and farm-yardmanure altogether naturally followed because the clearest possibleevidence--that of the profit and loss account--was available. Such falsereasoning is, alas, only too common in agriculture.
The reaction of the sugar-cane crop itself to this change in manuring wasinteresting. Two things happened: (1) insect and fungous diseasesincreased; (2) the varieties of cane showed a marked tendency to run out.These difficulties were met by a constant stream of new seedlingvarieties. In contrast to this behaviour of the cane on the large estatesis that of the same crop grown by the cultivators of northern India wherethe only manure used is cattle manure and where there is practically nodisease and no running out of varieties. The indigenous canes of theUnited Provinces have been grown for twenty centuries without any helpfrom mycologists, entomologists, or plant breeders.
Why does a variety of cane run out and why does it fall a prey todisease? Sugar-cane is propagated vegetatively from cuttings. When thebuds from which the new canes arise are grown with natural manure inIndia, the variety to all intents and purposes is permanent. On the sugarestates, however, when the buds are raised with chemicals the variety isshort-lived. There must be some simple explanation of this difference inbehaviour.
What happened in the early days of the sugar estates before the advent ofchemicals and before new seedling canes were discovered? In the WestIndies, for example, until the last decade of the last century theBourbon variety was practically the only kind grown. There was little orno disease and this old variety showed no tendency to run out. Theexperience of the cultivators of the United Provinces of India hastherefore been repeated on the estates themselves.
The simplest explanation of the breakdown of cane varieties is thatartificials do not really suit the cane and that they lead to incipientmalnutrition. If this is so the synthesis of carbohydrates and proteinswill be slightly imperfect: each generation of the cane will startsomewhat below par. The process will eventually end in a cane with adistinct loss in vegetative vigour and unable to resist the onslaughts ofthe parasite. In other words, the variety will have run out.
This hypothesis will be transformed into something approaching aprinciple if it can be proved that the cane is a mycorrhiza-former and isnourished in two ways: (1) by the carbohydrates and proteins synthesizedin the green leaves, and (2) the direct digestion of fungous mycelium inthe roots.
Steps were taken during 1938 and 1939 to have the roots of sugar-caneexamined in order to test this point of view. Material was obtained fromIndia, Louisiana, and Natal. In all cases the roots exhibited themycorrhizal association. The large amount of material sent from Natalincluded canes grown with artificials only, with humus only, and withboth. The results were illuminating. Humus is followed by theestablishment of abundant mycorrhiza and the rapid digestion of thefungus by the roots of the cane. Artificials tend either to eliminate theassociation altogether or to prevent the digestion of the fungus by theroots of the cane. These results suggest that the change over from penmanure to artificials is at the root of the diseases of the cane and isthe cause of the running out of the variety. We are dealing with theconsequences of incipient malnutrition--a condition now becoming verygeneral all over the world in many other crops besides sugarcane.
These observations leave little doubt that the future policy incane-growing must be the conversion of cane trash and other wastes intohumus. The difficulty in composting cane trash, however, is to start thefermentation and then to maintain it. The leaves are armour-plated and donot easily absorb water. Further, the material is low in nitrogen (about0.25 per cent.) while the ash (7.3 per cent. of the mass) contains 62 percent. of silica. The micro-organisms which manufacture humus find itdifficult to start on such refractory material. The problem is how bestto help them in their work: (1) by getting the trash to absorb water, and(2) by providing them with as much easily fermentable vegetable matter aspossible. Molasses where available can be used to help the fermentation.If humus of the highest quality is to be synthesized an adequate supplyof urine and dung must also be provided, otherwise a product without theaccessory growth substances will result. Given a reasonable supply ofurine and dung and sufficient easily fermentable vegetable wastes likegreen-manure, there is no reason why cane trash and the other wastes of asugar plantation cannot be made into first-class humus and why a sugarestate should not be made to manure itself. The conditions which must befulfilled are clear from the work already done. Dymond has shown thatbefore composting, cane trash must be allowed to weather a little: theweathered leaves must then be kept moist from the start. In this way thefungi and bacteria are greatly assisted. Filter press cake, dander, andother wastes all help in the process of conversion, as will be seen fromthe results of his various experiments carried out in 1938 in Natal(Table 2).
Composting cane trash in Natal
Composted Moisture Loss on N Total Available Total Avail. with ignition P205 P205 K20 K20
1. Kraal manure 60.5 30.6 0.74 0.28 0.14 S.T. --2. Filter cake 74.2 44.0 0.67 0.68 0.52 S.T. --3. Kraal manureand filter cake 61.0 33.3 0.71 0.40 0.28 S.T. --4. Kraal manure,filter cakeand molassas 64.8 34.6 0.70 0.40 0.20 T. S.T.5. Dunder 28.5 20.0 0.72 0.40 0.21 0.52 0.306. Kraal manure,filter cake,ammonium sulphate,and potassiumsulphate 59.2 27.8 1.00 0.42 0.29 0.72 0.497. Farm compostswith availablematerials 55.5 27.6 0.78 0.32 0.24 S.T. --8. Farm compostswith availablematerials 52.2 29.6 0.67 0.89 0.56 S.T. --9. Farm compostswith availablematerials 57.8 33.1 0.91 0.56 0.44 S.T. --10. Farm compostswith availablematerials 41.0 30.0 0.84 0.44 0.36 S.T. --11. Farm compostswith availablematerials 29.2 9.9 0.67 0.27 0.20 S.T. --
These results are similar to and confirm those obtained by Tambe and Wadat Indore in 1935. In Natal it is estimated that 100 tons of strippedcane will yield about 40 tons of compost containing about 280 lb. ofnitrogen and 160 lb. of phosphoric acid.
The main difficulty in composting cane trash must always be thecorrection of its wide carbon: nitrogen ratio. The problem is a practicalone--how best to bring the various wastes together in the cheapest wayand then distribute the finished humus to the land. Obviously there canbe no hard-and-fast procedure. The correct solution of the problem willvary with the locality: the work is such that it can only be done by theman on the spot.
The sugar estates of the future will in all probability gradually becomeself-supporting as regards manure. After a time no money will be spent onartificials. The change over from present methods of manuring will,however, take time, and at first a sufficient volume of high-qualityhumus will be out of the question because the animals maintained will betoo few.
What is the best way of using the small amount of humus that can be madeat the beginning? This is a very important matter. I suggest that itshould be devoted to the land on which the plant material is grown. Thesecanes should be raised in trenches on the Shahjahanpur principle (seeChapter XIV) and every care should be taken to maintain the aeration ofthe soil during the whole life of the crop. The trenches should be wellcultivated and manured with freshly prepared humus, at least three monthsbefore planting. These canes should be regarded as the most important onthe estate, and no pains should be spared to produce the best possiblematerial. Whether or not immature cane should continue to be planted is aquestion for the future. What is certain is that cane to be plantedshould be really well grown in a soil rich in freshly prepared humus.Each crop must start properly. As the supply of organic matter increaseson the sugar estates the methods found to give the best results ingrowing these canes can be extended to the whole estate.
That the above is possible is clear from a study of the work that hasbeen done in India and Natal. In March 1938 Dymond concluded a carefulsurvey of the whole problem in the following words:
'Artificials are easy of application, easily purchased in good times, ornot bought at all when times are bad; they form a never-ending topic ofconversation with one's neighbours, a source of argument with thevendors; they are a duty and a sop to one's conscience; whereas humusmeans more labour, more attention, transport and trouble. Nevertheless,humus is the basis of permanent agriculture, artificials the policy ofthe here to-day and gone to-morrow.'
Before taking up research on cotton at the newly founded Institute ofPlant Industry at Indore in 1924, a survey of cotton growing in thevarious parts of India was undertaken. At the same time the research workin progress on this crop was critically examined.
The two most important cotton-growing areas in India are: (1) the blackcotton soils of the Peninsula, which are derived from the basalt; (2) thealluvium of North-West India, the deposits left by the rivers of theIndo-Gangetic plain.
In the former there are thousands of examples which indicate beyond alldoubt the direction research on this crop should take. All round thevillages on the black cotton soils, zones of highly manured land rich inorganic matter occur. Here cotton does well no matter the season: theplants are well grown and free from pests: the yield of seed cotton ishigh. On the similar but unmanured land alongside the growth iscomparatively poor: only in years of well distributed rainfall is theyield satisfactory. The limiting factor in growth is the development,soon after the rains set in, of a colloidal condition which interfereswith aeration and impedes percolation. This occurs on all black soils,but organic matter mitigates the condition.
On the alluvium of North-West India, a similar limiting factor occurs.Here cotton is grown on irrigation, which first causes the fine soilparticles to pack and later on to form colloids. In due course theAmerican varieties in particular show by their growth that they are notquite at home. The anthers often fail to function properly, the plantsare unable to set a full crop of seed, the ripening period is undulyprolonged, and the fibre lacks strength, quality, and life. The cause ofthis trouble is again poor soil aeration, which appears in these soils tolead to a very mild alkali condition. This, in turn, prevents the cottoncrop from absorbing sufficient water from the soil. One of the easiestmethods of preventing this packing is by assisting the soil to formcompound particles with the help of dressings of humus.
The basis of research work on cotton in India was therefore disclosed bya study in the field of the crop itself. The problem was how best tomaintain soil aeration and percolation. This could be solved if morehumus could be obtained. Good farming methods therefore provided the keyto the cotton problems of India.
A study of the research work which has been done all over the world didnothing to modify this opinion. The fundamental weakness in cottoninvestigations appeared to be the fragmentation of the factors, a loss ofdirection, failure to define the problems to be investigated, and ascientific approach on far too narrow a front without that balance andstability provided by adequate farming experience.
Steps were therefore taken to accelerate the work on the manufacture ofhumus which had been begun at the Pusa Research Institute. The IndoreProcess was the result. It was first necessary to try it out on thecotton crop. The results are summed up in the following Table:
The increase general fertility at Indore
Year Area in acres of Average yield Yield of the best plot Rainfall improved land in lb. per of the year in in inches under cotton acre lb. per acre
1927 20.60 340 384 27.79 (distrib. good)1928 6.64 510 515 40.98 (a yr of excessive rain)1929 36.98 578 752 23.11 (distribution poor)
The figures show that, no matter what the amount and distribution ofrainfall were, the application of humus soon trebled the average yield ofseed cotton--200 lb. per acre--obtained by the cultivators on similarland in the neighbourhood.
In preparing humus at Indore one of the chief wastes was the old stalksof cotton. Before these could be composted they had to be broken up. Thiswas accomplished by laying them on the estate roads, where they were soonreduced by the traffic to a suitable condition for use as bedding for thework-cattle prior to fermentation in the compost pits.
The first cotton grower to apply the Indore Process was Colonel (now SirEdward) Hearle Cole, C.B., C.M.G., at the Coleyana Estate in theMontgomery District of the Punjab, where a compost factory on the linesof the one at the Institute of Plant Industry at Indore was establishedin dune 1932. At this centre all available wastes have been regularlycomposted since the beginning: the output is now many thousands of tonsof finished humus a year. The cotton crop has distinctly benefited by theregular dressings of humus; the quality of the fibre has improved; higherprices are being obtained; the irrigation water required is now one-thirdless than it used to be. The neighbouring estates have all adoptedcomposting: many interested visitors have seen the work in progress. Oneadvantage to the Punjab of this work has, however, escaped attention,namely, the importance of the large quantities of well-grown seed, raisedon fertile soil, contributed by this estate to the seed distributionschemes of the Provincial Agricultural Department. Plant breeding to besuccessful involves two things--an improved variety plus seed fordistribution grown on soil rich in humus.
The first member of an Agricultural Department to adopt the Indore Methodof composting for cotton was Mr. W. J. Jenkins, C.I.E., when ChiefAgricultural Officer in Sind, who proved that humus is of the greatestvalue in keeping the alkali condition in check, in maintaining the healthof the cotton plant, and in increasing the yield of fibre. At Sakrand,for example, no less than 1,250 cartloads of finished humus were preparedin 1934-5 from waste material such as cotton stalks and crop residues.
During recent years the Indore Process has been tried out on some of thecotton farms in Africa belonging to the Empire Cotton GrowingCorporation. In Rhodesia, for example, interesting results have beenobtained by Mr. J. E. Peat at Gatooma. These were published in theRhodesia Herald of August 17th, 1939. Compost markedly improved the fibreand increased the yield not only of cotton but also of the rotationalcrop of maize.
Why cotton reacts so markedly to humus has only just been discovered. Thestory is an interesting one, which must be placed on record. In July 1938I published a paper in the Empire Cotton Growing Review (vol. xv, no. 3,1938, p. 186) in which the role of the mycorrhizal relationship in thetransmission of disease resistance from a fertile soil to the plant wasdiscussed. In the last paragraph of this paper the suggestion was madethat mycorrhiza 'is almost certain to prove of importance to cotton andthe great differences observed in Cambodia cotton in India, in yield aswell as in the length of the fibre, when grown on (1) garden land (richin humus) and (2) ordinary unmanured land, might well be explained bythis factor'. In the following number of this Journal (vol. xv, no. 4,1938, p. 310) I put forward evidence which proved that cotton is amycorrhiza-former. The significance of this factor to the cotton industrywas emphasized in the following words:
'As regards cotton production, experience in other crops, whose rootsshow the mycorrhizal relationship, points very clearly to what will benecessary. More attention will have to be paid to the well tried methodsof good farming and to the restoration of soil fertility by means ofhumus prepared from vegetable and animal wastes. An equilibrium betweenthe soil, the plant and the animal can then be established andmaintained. On any particular area under cotton, a fairly definite ratiobetween the number of live stock and the acreage of cotton will beessential. Once this is secured there will be a marked improvement in theyield, in the quality of the fibre and in the general health of the cropAll this is necessary if the mycorrhizal relationship is to act and ifNature's channels of sustenance between the soil and the plant are tofunction. Any attempt to side-track this mechanism is certain to fail.
'The research work on cotton of to-morrow will have to start from a newbase line--soil fertility. In the transition between the research ofto-day and that of the future, a number of problems now underinvestigation will either disappear altogether or take on an entirely newcomplexion. A fertile soil will enable the plant to carry out thesynthesis of proteins and carbohydrates in the green leaf to perfection.In consequence the toll now taken by fungous, insect and other diseaseswill at first shrink in volume and then be reduced to its normalinsignificance. We shall also hear less about soil erosion in places likeNyasaland where cotton is grown, because a fertile soil will be able todrink in the rainfall and so prevent this trouble at the source.'
Confirmation of these pioneering results soon followed. In theTransactions of the British Mycological Society (vol. xxii, 1939, p. 274)Butler mentions the occurrence of mycorrhiza as luxuriantly developed incotton from the Sudan and also in cotton from the black soils of Gujerat(India). In the issue of Nature of July 1st, 1939, Younis Sabet recordedthe mycorrhizal relationship in Egypt. In the Empire Cotton GrowingReview of July 1939 Dr. Rayner confirmed the existence of mycorrhiza inboth Cambodia and Malvi cotton grown at my suggestion by Mr. Y. D. Wad atIndore, Central India, in both black cotton soil and in sandy soil fromRajputana.
As is well known, the leaves of the sisal plant yield about 93 per cent.of waste material and about 7 per cent. of fibre, of which not more than5 per cent. is ordinarily extracted. The wastes are removed from thedecorticators by a stream of water, usually to some neighbouring ravineor hollow in which they accumulate. Sometimes they are led into streamsor rivers. The results are deplorable. Putrefaction takes place in thedumps and nuisance results, which can be detected for miles. The streamsare contaminated and the fish are killed. On account of these primitivemethods of waste disposal, the average sisal factory is a most depressingand disagreeable spot. Further, the water used in these operations--whichhas to be obtained at great expense by sinking wells or boreholes, bymaking dams or reservoirs, and then raised by pumping plants--is allowedto run to waste. Two of the pressing problems, therefore, of the sisalindustry are: (1) the conversion of the solid residues, including theshort fibres, into some useful product like humus, and (2) the use of thewaste water for raising irrigated crops.
These two problems have been successfully solved on Major Grogan's estateat Taveta in Kenya, by the Manager, Major S. C. Layzell, M.C. The workbegan in 1935 and has been steadily developed since. An account of theresults was published in the East African Agricultural Journal of July1937.
The first problem was to separate the liquid in the flume waste from thesolids. At Taveta all the waste from the decorticator is passed over agrid at the end of the flume. The grid retains the solids and allows theacid 'soup' to pass into a concrete sump below, from which it is carriedby a suitably graded channel, with a fall of 1 in 1,000, to the irrigatedarea. From the grid the solid waste is moved on slatted trucks (the usualfour-wheel frame constructed of timber with a platform of slats arrangedat right angles to the track) to a concrete basin where they are allowedto drain The drainage water from this basin is led by a small irrigationfurrow to another area where it is utilized for growing crops. There arethus two sources of irrigation water--the main flume water and thedrainage from the loaded trucks
(Plate I).(not in etext)CONVERSION OF SISAL WASTE.Above: Filtering the waste.Middle: Draining.Below: Irrigation with waste-water.
The lay out of the composting ground is important. Sisal poles, in groupsof four, equally spaced, are arranged on both sides and at right anglesto the rail track. On these poles, placed a foot apart for providingaeration from below, the waste is lightly spread to a height of 2 feetin heaps measuring 15 feet by 4 feet. As all new heaps require a starter,any estate making compost for the first time should obtain a small supplyof freshly made humus from some other sisal estate which has adopted theIndore Process. A few handfuls of this old compost, distributed evenlyin the heaps, is sufficient to start fermentation. The waste is lefton the poles for thirty days during which the breaking-down process,by means of thermophyllic bacteria, begins. The temperature rises toa point where it is impossible to bear one's hand in the heap.
The first turn takes place thirty days after the first formation of theheap when the contents of two heaps are run together into one, as by thistime the volume has considerably decreased. After the first turn thedecomposition is carried a stage further, mainly by fungi. During thisphase the whole heap is often covered each morning with a long-stemmedtoadstool (Plate II).
PLATE II.(not in etext)CONVERSION OF SISAL WASTE.Above: Light railway and foundation of sisal poles.Middle: Spreading.Below: Turned heaps with layers of elephant grass.
At the end of another thirty days the second turn takes place. Theripening process then begins and is completed about the ninetieth dayafter the original heaps were made. Major Layzell writes that the finalproduct resembles first-class leaf mould and contains 1.44 per cent. ofnitrogen. On the basis of its chemical composition alone the compost hasbeen valued locally at 2 pounds a ton.
A large portion of the humus is devoted to the sisal nurseries in orderthat all new areas can be started with vigorous and properly grownplants. The remainder finds its way to the areas producing sisal.
The sisal plant only does well on fertile soil and therefore needsintensive rather than extensive cultivation. Whenever this is forgottenthe enterprise ends in bankruptcy for the reason that, as the soil nearthe factory is exhausted, the lead to the decorticators soon eats up theprofit. The game is no longer worth the candle. The conversion of thewastes into humus will therefore solve this problem: the fertility of theland round the factory can be maintained and even improved. Further, thedumps of repulsive sisal waste will be a thing of the past.
The labour employed in dealing with the waste and turning the heaps froma decorticator producing 120 tons of fibre per month is thirty-four withtwo head men. Sixteen additional men were taken up on the grid and withthe trucks, so that a labour force of fifty in all with two head men wasneeded for making compost at this centre. There is no difficulty inhandling sisal wastes provided the workmen are given a supply of somecheap oil for protecting the skin, otherwise the juice of the leavesproduces eczema on the arms and legs of those engaged on the work.
The flume liquid is mainly used for growing food crops for the labourforce so as to improve the usual set ration of mealie-meal, beans, andsalt. The psychological effect of all this on the labourers has beenremarkable: the spectacle of a large area of bananas, sugar-cane, citrusplants, and potatoes removes all fear of a possible lack of food from theminds of the workers and their families: they feel safe. Further, theirphysical health and their efficiency as labourers rapidly improve. Aguaranteed food-supply has proved a great attraction to labour and hasprovided a simple and automatic method of recruitment.
At Taveta the soil contains a good deal of lime so that the priorneutralization of the acid irrigation water is unnecessary. On otherestates this point might have to receive attention. Perhaps the easiestway to get rid of the acidity would be to add sufficient powdered crudelimestone to the flume water just after the solids have been separatedfor composting.
Two conditions must be fulfilled before the methods worked out at Tavetacan be adopted elsewhere: (1) there must be a suitable area of flat landnear the factory for growing irrigated crops; (2) the general layout mustbe such that there is ample room for a composting ground to which thewastes can be taken by a light railway and from which the finished humuscan be easily transported to the irrigated area and to the rest of theestate.
One obvious improvement in the manufacture of humus on a sisal estatemust be mentioned. Animal residues must be added to the vegetable wastes.If it is impossible to maintain sufficient live stock for all the sisalwaste, two grades of humus should be made: first grade with animal manurefor the parent plants and the nurseries, second grade for the plantswhich yield fibre.
One of the great weaknesses in British agriculture at the moment is thedependence of our live stock--such as pigs, poultry, and dairyanimals--on imported foodstuffs. Our animal industry is becoming just asunbalanced as regards the supply of nutriment grown on fertile soil asour urban population. One of the animal foods imported in largequantities is maize. Unfortunately a large proportion of this import isbeing grown on worn-out soils. We are feeding our animals and indirectlyourselves on produce grown anywhere and anyhow so long as it is cheap.
Mother earth, however, has registered an effective protest. The maizesoils of such areas as Kenya and Rhodesia soon showed signs ofexhaustion. The yields fell off. Any one who has had any practicalexperience of maize growing could have foretold this. This crop requiresa fertile soil.
The maize growers of Kenya, Rhodesia, and South Africa soon learnt thislesson. The constant cropping of virgin land with an exhausting croprapidly reduced the yield. This happened just as the Indore Process wasdevised. Its application to the maize fields of Kenya and Rhodesia led togood results. The composting of the maize stalks and other vegetableresidues, including green-manure crops, was taken up all over Kenya andRhodesia.
Two examples out of many of the results which are being obtained may bequoted: at Rongai in Kenya, Mr. J. E. A. Wolryche Whitmore has adoptedthe Indore Process on three farms. The working oxen are being bedded downduring the night with dry maize stalks, wheat-straw, grass, and otherroughage available. After a week under the cattle this is composted inpits with wood-ashes and earth from under the animals. If insufficientearth is used a high temperature is not maintained. Two turns atintervals of a month yield a satisfactory product after ninety days. Theeffect on the maize crop is very marked. In Rhodesia, Captain J. M.Moubray has obtained similar results. (These are described in detail inAppendix B).
One of the pests of maize in Rhodesia--the flowering parasite knownlocally as the witch-weed (Striga lutea)--can be controlled by humus.This interesting discovery was made by Timson whose results werepublished in the Rhodesia Agricultural Journal of October 1938. Humusmade from the soiled bedding in a cattle kraal, applied at the rate of 10tons to the acre to land severely infested with witch-weed, was followedby an excellent crop of maize practically free from this parasite. Thecontrol plot alongside was a red carpet of this pest. A second crop ofmaize was then grown on the same land. Again it was free from witch-weed. This parasite promises to prove a valuable censor for indicatingwhether or not the maize soils of Rhodesia are fertile. If witch-weedappears, the land needs humus; if it is absent, the soil containssufficient organic matter. Good farming will therefore provide anautomatic method of control.
Humus is bound to affect the quality of maize as well as the yield. Inthe interests both of the maize-exporting and the maize-importingcountries, a new system of grading and marketing the produce of fertilesoil should be introduced. Maize grown on land manured with properly madehumus and without the help of artificials should be so described andgraded. Only in this way can well-grown produce come into its own. Itshould be clearly distinguished in its journey from the field to theanimal and kept separate from inferior maize. Purchasers will then knowthat such graded produce fed to their live stock will have been properlygrown. They will soon discover that it suits their animals. This questionof grading produce according to the way it is grown applies to many othercrops besides maize. Its importance to the future of farming and thehealth of the nation is referred to in a later chapter.
By far the most important food crop in the world is rice. It will beinteresting therefore to see what response this cereal makes to humus. Weshould expect it would be considerable, because the rice nurseries arealways heavily manured with animal manure and just before transplantingthe seedlings are much richer in nitrogen than at any further stage inthe life of the plant.
The first trial of the Indore Process was made by the late Mrs. Kerr atthe Leper Home and Hospital, Dichpali in H.E.H. the Nizam's Dominions.Her reaction after reading The Waste Products of Agriculture in 1931 was:'If he is right it will mean the utter economic revolution of India'svillages.' Rice was selected as the crop on which to test the method. Shedied while the trial was in progress. The results are summed up in aletter from her husband, the Rev. G. M. Kerr, dated Dichpali, November2nd, 1933, as follows:
'We have cut three and entirely average portions of our rice fields. No.1 plot had 1.25 to 1.5 inches of Indore compost ploughed in. No. 2 plothad some farm rubbish plus 3/8 inch of Indore compost. No. 3 plot was thecontrol and had nothing.
'Since we are eager to get these figures off to you the tabulated weightresults of the straw cannot be given. Plot No. I was cut It days ago;plot No. 2 only 2 days ago, and plot No. 3 yesterday. No. 1, therefore,is dry, and Nos. 2 and 3 are still wet. We have given the straw resultsin similar sized bundles, but No. 1 is the better straw and will makeconsiderably better buffalo fodder (Table 4).
'Once we get all our 30 acres of rice fields fully composted we shall beable to welcome 50 or 60 more lepers here for cleansing. This is not ascientific conclusion according to your usual methods of reckoning, butit is the practical issue as it appeals to us.'
In a subsequent letter dated October both, 1935, the Dichpali experienceof the Indore Process was summed up as follows:
'Indore compost is one of the material blessings of this life, likesteam, electricity and wireless. We simply could not do without it here.It has transformed all our agricultural interests. We have 43 acres underwet cultivation, and most of the land three years ago was of the poorestnature, large patches of it so salty that a white alum-like powder lay onthe surface. We have now recovered 28 acres, and on these we are having abumper crop of rice this year. There have never been such crops grown onthe land, at least not for many years. The remaining 15 acres are asbefore with the rice scraggy and thin. By means of our factory of 30 pitswe keep up a supply of compost, but we can never make enough to meet ourneeds. We are now applying it also on our fields of forage crops withremarkable results. Compost spread over a field to the depth of about onequarter of an inch ensures a crop at least three or four times heavierthan otherwise could be obtained.'
Crop results of three plots of rice grown under varying conditionsat the Home for Lepers, Dichpali
No. 1 Plot No. 2 Plot No. 3 Plot
Amount of land measured for the contrast. All portions had the same cultivation 6,394 sq. ft. 6,394 sq. ft. 6,394 sq. ft.
Amount of seed sown. All the seedsown was the same quality 6 lb. 6 lb. 6 lb.
Amount of rice taken in each caseby measure, not weight 422 lb. 236 lb. 60 lb.
Amount of straw in similarsized bundles 138 bundles 106 bundles 40 bundles
The marked response of rice to organic matter in the rice nurseries iswell known. The Dichpali results prove that the transplanted crop alsoresponds to humus. In the nurseries the soil conditions are aerobic:after transplanting, the roots of the crops are under water, when theoxygen supply largely depends on the activities of algae. How does humusinfluence the rice plant in water culture under conditions when theactive oxygen must be dissolved in water? Do the roots of rice in thenurseries and also after transplanting exhibit the mycorrhizalrelationship? If they do, the explanation of the Dichpali results issimple. If they do not, how then does humus in wet cultivation influencephotosynthesis in the green leaf? Nitrification of the organic matterwould seem difficult under such conditions for two reasons: (1) theprocess needs abundant air; (2) the nitrate when formed would undergoexcessive dilution by the large volume of water in the rice fields. If,however, the mycorrhizal association occurs in transplanted rice, theDichpali results explain themselves.
While this book was passing through the press specimens of surface rootsof transplanted rice, 116 days from the date of sowing, grown in soilmanured with humus, were collected on October 27th, 1939, by Mr. Y. D.Wad in Jhabua State, Central India. They were examined by Dr. IdaLevisohn on December 11th, 1939, whose report reads as follows:
'The stouter laterals of the first order show widespread endotrophicmycorrhizal infection, the mycorrhizal regions being indicatedmacroscopically by opacity, beading and the absence of root hairs. Theactive hyphae are of wide diameter; they pass easily through the cellwalls and form coils, vesicles and arbuscles; they show the early andlater stages of digestion. The resulting mass of granular materialappears to be rapidly translocated from the cells.'
There is no doubt that rice is a mycorrhiza-former, a fact which at onceexplains the remarkable response of this crop to humus and which opens upa number of new lines of investigation. Yield, quality, diseaseresistance, as well as the nutritive value of the grain will in allprobability be found to depend on the efficiency of the mycorrhizalassociation.
One of the chief problems in market gardening in the open and under glassis the supply of humus. In the past, when horse transport was the ruleand large numbers of these animals were kept in the cities, it was thecustom, near London for example, for the wagons which brought in thecrates of vegetables for the early morning market to take back a load ofmanure. The introduction of the internal combustion engine changed this:a general shortage of manure resulted. In most cases market gardens arenot run in connexion with large mixed farms, so there is no possibilityof making these areas self-supporting as regards manure: the essentialanimals do not exist. The result is that an increasing proportion of thevegetables sold in the cities is raised on artificial manure. In this waya satisfactory yield is possible, but in taste, quality, and keepingproperties the product is markedly inferior to the vegetables raised onfarm-yard manure.
It is an easy matter to distinguish vegetables raised on NPK. They aretough, leathery, and fibrous: they also lack taste. In marked contrastthose grown with humus are tender, brittle, and possess abundant flavour.One of the lessons in dietetics which should be taught to children inevery school and institution in the country, and also in every home,should be the difference between vegetables, salads, potatoes, and fruitgrown with humus or with artificials. Evidence is accumulating thatliability to common ailments like colds, measles, and so forth becomesmuch less when the vegetables, fruit, potatoes, and other food consumedare raised from fertile soil and eaten fresh.
How is the necessary humus for the high-quality vegetables needed byurban areas to be obtained? Two solutions of the problem are possible.
In the first place, market gardening should, whenever possible, beconducted as a branch of mixed farming with an adequate head of livestock, so that all the waste products, vegetable and animal, of theentire holding can be converted into humus by the Indore Process. Thefirst trial of this system was carried out at the Iceni Nurseries,Surfleet, Lincolnshire. The work commenced in December 1935 and can bestbe described in Captain Wilson's own words taken from a memorandum hedrew up for the members of the British Association who visited his farmon September 4th, 1937:
'The Iceni Estate consists of about 325 acres comprised as follows:--Arable land, etc. . . . . . . . . . . 225 acresPermanent grassland . . . . . . . . . 30Rough wash grazings . . . . . . . . . 35Land under intensive horticulture . . 35
'The main idea in the development of the estate has been to prove thateven to-day, in certain selected areas of England, it is a commercialproposition to take over land which has been badly farmed, and bring itback to a high state of fertility, employing a large number of personsper acre.
'To this end the estate has been developed as a complete agriculturalunit with a proper proportion of live stock, arable land, grass landand horticulture, with the belief that after a few years of propermanagement the estate can become very nearly, if not entirely, aself-supporting unit, independent of outside supplies of chemical manures,etc., and feeding stuffs, the land being kept in a high state offertility, which is quite unusual to-day, by:
(1) A proper balance of cropping.
(2) The conversion of all wheat straw into manure in the crew yards andthe utilization of this manure and as much as possible of the wasteproducts of the land for making humus for the soil.
'As regards (2), the method of humus-making which has been employed isknown as "The Indore Process", and it has proved successful. The outputin 1936 amounted to approximately 700 tons, and in the current year willprobably be about 1,OOO tons.
'As a result of this utilization of humus, the land under intensivecultivation has already reached a state of independence, and for the lasttwo years no chemicals have been used in the gardens at all either asfertilizers or as sprays for disease and pest control. The only washwhich has been used on the fruit trees is one application each winter oflime sulphur, and it is hoped to eliminate this before long.
'The farm land is not yet independent of the purchase of fertilizers,but the amount used has been steadily reduced from 106 tons used in 1932,costing 675 pounds, to 40-1/2 tons in the current year, costing 281pounds. Similarly the potato crop, which formerly was sprayed four orfive times, is now only sprayed once, and this it is hoped will also bedispensed with before many years when the land has become healthy and ina proper state of fertility.
'Eventually, with a properly balanced crop rotation, there is no doubtin my mind that the same degree of independence can be reached on thefarm as has already been attained on my market-garden land.
'The probable cropping will eventually work out as follows:
75 acres potatoes.75 acres wheat.25 acres barley, oats, beans and linseed (for stock feeding).15 acres roots (for stock feeding).30 acres one year clover and rye-grass leys for feeding with pigs andpoultry and cutting for hay, ploughing in the aftermath.
'The live stock carried on the farm at the June returns was as follows:22 cattle (cows and young stock of my own breeding).
14 horses (including foals).15 sows (for breeding).103 other pigs.12O laying hens (of my own stock).
'And although it is rather early to say, I believe that the abovefigures may be about right for the size of the farm, with the additionof about So cattle for winter yard feeding. This latter importation willbe rendered unnecessary in a few years when the number of cattle of myown breeding will have increased.'
Since this memorandum a further advance has been made at Surfleet. Thefactor which at present limits production on the alluvial soils in theHolland Division of Lincolnshire (in which Captain Wilson's vegetablegarden is situated) is undoubtedly soil aeration. These soils packeasily, so the supply of oxygen for the micro-organisms in the soil andfor the roots of the crops is frequently interrupted. Sub-soil drainagetends to reduce this adverse factor. During the autumn of 1937 the wholeof Captain Wilson's vegetable area was pipe drained. As was expected, theimprovement in soil aeration which instantly followed has enabled thecrops to obtain the full benefit of humus. Here is a definite examplewhere the establishment of Nature's equilibrium between the soil, theplant, and the animal has resulted in increased crops and in higherquality produce.
Another and perhaps a simpler solution of the organic matter problem invegetable growing is to make use of the millions of tons of humus in thecontrolled tips in the neighbourhood of our cities and towns. Thissubject is discussed in detail in Chapter VIII.
A comparison between the cultivation of the vine in the East and the Westis interesting in more than one respect. In the Orient this crop is grownmostly for food: in the Occident, including Africa, most of the grapesare made into wine.
The feature of the cultivation of the vine in Asia is the long life ofthe variety, the universal use of animal manure, and the comparativeabsence of insect and fungous diseases. Artificial manures, sprayingmachines, and poison sprays are unknown.
In the West the balance between the area under vines and the number oflive stock has been lost: the vine has largely displaced the animal: theshortage of farm-yard manure has been made up by the chemical fertilizer:the life of the variety is short: insect and fungous diseases areuniversal: the spraying machine and the poison spray are to be seeneverywhere: the loss of balance in grape growing has been accompanied bya lowering in the quality of the wine.
During the last three summers, in the course of extensive tours inProvence, a sharp look-out was kept for vineyards in which the appearanceof the vines tallied in all respects with those of Central Asia, namely,well-grown plants which looked thoroughly at home, and in which thefoliage and young growth possessed real bloom. At last near the villageof Jouques in the Department of Bouches du Rhone such vines were found.They had never received any artificials, only animal manure: the vineyardhad a good local reputation for the quality of its wine. Arrangementswere made with the proprietress to have the active roots examined. Theyexhibited the mycorrhizal association. The vine is a mycorrhiza--formerand therefore humus in the soil is essential for perfect nutrition; thelong life of the variety and the absence of disease in Central Asia areat once explained.
In a recent survey of fruit growing in the Western Province of the Unionof South Africa, which appeared in the Farmer's Weekly (Bloemfontein) ofAugust 23rd, 1939, Nicholson refers to a local vineyard, on the main roadbetween Somerset West and Stellenbosch, which has taken up the IndoreProcess:
'Motorists travelling along this road cannot help noticing how healthythis farmer's vineyards look and how orderly is the whole farm. Earlythis winter I visited it in time to see the huge stacks ofmanure--beautiful, finely rotted bush which had been helped to reach thatstate by being placed in the kraal under the animals. Pigs had playedtheir part too. During the wine-pressing season all the skins of thegrapes are fed to the pigs and later returned to the vineyards in theform of manure.'
When the vine growers of Europe realize how much they are losing by anunbalanced agriculture in the shape of the running out of the variety,loss of resistance to disease, and loss of quality in the wine, stepswill no doubt be taken by a few of the pioneers to increase the head oflive stock, to convert all the available wastes into humus, and to getback to Nature as quickly as possible.
DYMOND, G. C. 'Humus in Sugar-cane Agriculture', South African SugarTechnologists, 1938.
HOWARD, A. 'The Manufacture of Humus by the Indore Process,, Journal ofthe Royal Society of Arts, lxxxiv, 1935, P. 25 and lxxxv, 1936, p. 144.
------'Die Erzeugung von Humus nach der Indore-Methode',Der Tropenpflanzer, xxxix, 1936, p. 46.
-------'The Manufacture of Humus by the Indore Process', Journal ofthe Ministry of Agriculture, xiv, 1938, p. 431.
'En Busca del Humus', Revista del Istituto de Defensa del Cafe deCosta Rica, vii, 1939, P. 427.
LAYZELL, S. C. 'The Composting of Sisal Wastes', East AfricanAgricultural Journal, iii, 1937, P 26
TAMBE, G. C., and WAD, Y. D. 'Humus-manufacture from Cane-trash',International Sugar Journal, 1935, p. 260.
DEVELOPMENTS OF THE INDORE PROCESS
Since Schultz-Lupitz first showed about 1880 how the open sandy soils ofNorth Germany could be improved in texture and in fertility by theincorporation of a green crop of lupine, the possibilities of this methodof enriching the land have been thoroughly explored by the ExperimentStations. After the role of the nodules on the roots of leguminous plantsin the fixation of atmospheric nitrogen was proved, the problems ofgreen-manuring naturally centred round the utilization of the leguminouscrop in adding to the store of combined nitrogen and organic matter inthe soil. At the end of the nineteenth century it seemed so easy, bymerely turning in a leguminous crop, to settle at one stroke and in avery economical fashion the great problem of maintaining soil fertility.At the expenditure of a little trouble, the leguminous nodule might beused as a nitrogen factory while the remainder of the crop could providehumus. All this might be accomplished at small expense and without anyserious interference with ordinary cropping. These expectations, anatural legacy of the NPK mentality, have led to innumerablegreen-manuring experiments all over the world with practically everyspecies of leguminous crop. In a few cases, particularly in open,well-aerated soils where the rainfall after the ploughing in of the greencrop was well distributed and ample time was given for decay, the resultshave been satisfactory. In the majority of cases, however, they have beendisappointing. It will be useful, therefore, to examine the whole subjectand to determine if possible the reasons why this method of improving thefertility of the soil seems so often to have failed.
A consideration of the factors involved in the growth, decay, andutilization of the residues of a green crop will at once explain thegeneral failure of green-manuring to increase the following crop and alsoput an end for all time to the somewhat extravagant hopes of repeatingthe German results, which succeeded because all the factors, includingtime, happened to be favourable. It is no use slavishly copying thismethod unless we can at the same time reproduce the North German soil andclimatic conditions.
The chief factors in green-manuring are: (1) knowledge of the nitrogencycle in relation to the local agriculture; (2) the conditions necessaryfor rapid growth and also for the formation of abundant nodules on theroots of the leguminous crop used for green-manuring; (3) the chemicalcomposition of the green crop at the moment it is ploughed in; (4) thesoil conditions during the period when decay takes place. These fourfactors must be studied before the possibilities of green-manuring can beexplored.
The importance of the nitrogen cycle in relation to the local agricultureis a factor in green-manuring to which far too little attention has beenpaid. As will be shown more fully in Chapter XIV, the full possibilitiesof green-manuring can only be utilized when we know at what periods ofthe year nitrate accumulations take place, how these accumulations fit inwith the local agricultural practice, and when nitrates are liable to belost by leaching and other means. If the crop does not make the fullestuse of nitrate, this precious substance must be immobilized by means ofgreen-manure or by means of weeds and algae. It must not be left to takecare of itself. It must either be taken up by the crop or banked by someother plant.
The soil conditions necessary for the growth of the leguminous crop usedas a green-manure have never been sufficiently studied. Clarke found atShahjahanpur in India that it was advantageous to apply a small dressingof farm-yard manure to the land just before the green crop is sown. Theeffect of this is to stimulate growth and nodular development in aremarkable way. Further, the green crop when turned in decays much fasterthan when this preliminary manuring is omitted. It may be that besidesstimulating nodular development the small dressing of farm-yard manure isnecessary to bring into effective action the mycorrhizal associationwhich is known to exist in the roots of most leguminous plants. Thisassociation is a factor which has been completely forgotten ingreen-manuring. There is no reference to it in Waksman's excellentsummary on pp. 208-14 of the last edition of his monograph on humus. Thisfactor will probably also prove to be important in the utilization of thehumus left by green-manuring.
The living bridge between the humus in the soil and the plant must beproperly fed, otherwise the nutrition of the crop we wish to benefit isalmost certain to suffer.
As growth proceeds the chemistry of a green crop alters veryconsiderably: the material in a young or in a mature crop, when presentedto the micro-organisms of the soil, leads to very different results.Waksman and Tenney have set out the results of the decomposition of atypical green-manure plant (rye) harvested at different periods ofgrowth. When the plants are young they decompose rapidly: a large part ofthe nitrogen is released as ammonia and becomes available. When theplants are mature they decompose much more slowly: there is insufficientnitrogen for decay, so the micro-organisms utilize some of the soilnitrates to make up the deficiency. Instead of enriching the soil inavailable nitrogen the decay of the crop leads to temporaryimpoverishment. These fundamental matters are summed up in the followingTable:
Rapidity of decomposition of rye plants at different stages of growth(Waksman and Tenney)
Two grammes of dry material decomposed for 27 days
Stage of growth CO2 given off Nitrogen liberated Nitrogen cnsumed from (mg. C) as ammonia (mg. N) the media(mg. N)
Plants only25-35 cm. high 286.8 22.2 0
Just before headsbegin to form 280.4 3.0 0
Just before bloom 199.5 0 0
Plants nearlymature 187.9 0 8.9
The amount of humus which results from the decay of a green crop alsodepends on the age of the plants. Young plants, which are low in ligninand in cellulose, leave a very small residue of humus. Mature plants,on the other hand, are high in cellulose and lignin and yield a largeamount of humus. These differences are brought out in Table 6.
It follows from these results that if we wish to employ green-manuringto increase the soil nutrients quickly, we must always plough in thegreen crop in the young stage; if our aim is to increase the humus contentof the soil we must wait till the green-manure crop has reached itsmaximum growth.
The soil conditions after the green crop is ploughed in are no lessimportant than the chemical composition of the crop. The micro-organismswhich decay the green-manure require four things: (1) sufficient combinednitrogen and minerals; (2) moisture; (3) air; (4) a suitable temperature.These must all be provided together.
Formation of humus during decomposition of rye plants at different stagesof development
(Waksman and Tenney)
Chemical constituents At beginning of At the end of At the end of decomposition* decomposition decomposition** mg. mg. % of original
JUST BEFORE HEADS BEGIN TO FORM
Total water-insolubleorganic matter 7,465 2,015 27.0Pentosans 2,050 380 18.5Cellulose 2,610 610 23.4Lignin 1,180 750 63.6Protein insolublein water 816 253 31.0
PLANTS NEARLY MATURE
Total water-insolubleorganic matter 15,114 8,770 58.0Pentosans 3,928 1,553 39.5Cellulose 6,262 2,766 44.2Lignin 3,403 3,019 88.7Protein insolublein water 181 519 286.7
* 10 gm. material (on dry basis) used for young plants and 20 gm.for old plants.** 30 days for young plants and 60 days for mature plants.
The factor which so often leads to trouble is the poverty of thesoil--insufficient combined nitrogen and minerals. It follows, therefore,that when a mature crop is ploughed in the effect of its decay on thenext crop will always depend on the fertility of the soil. If the soil isin a poor condition most of the combined nitrogen available will beimmobilized for the decay of the green-manure; the next crop will sufferfrom starvation; green-manuring will then be a temporary failure. If,however, the soil is fertile or if we plough in freshly prepared humuswith the green crop, the extra combined nitrogen needed for decay willthen be present; the next crop will not suffer. Soil fertility in this,as in so many other matters, gives the farmer considerable latitude. Allsorts of things can be done with perfect safety with a soil in good heartwhich are out of the question when the soil is infertile. A good reserveof fertility, therefore, will always be an important factor ingreen-manuring.
As the decomposition of a green crop is carried out by microorganisms,decay ceases if the moisture falls below a certain point.
Again, if the air supply is cut off by excessive rain after ploughing inor by burying the green crop too deeply, an anaerobic soil flora rapidlydevelops which proceeds to obtain its oxygen supply from the substratum.The valuable proteins are attacked and their nitrogen is released as gas.The chemical reactions of the peat bog replace those of the early stagesof a properly managed compost heap. This frequently happens under monsoonconditions and is one of the reasons why green-manuring is so oftenunsatisfactory in tropical agriculture.
Finally, the temperature factor is important in countries like GreatBritain which have a winter. Here green-manure crops must often be turnedin during the autumn before the soil gets too cold, so that the earlystages of decay can be completed before winter comes.
The uses of green-manuring in agriculture can now be considered.Generally speaking they fall into three classes: (1) the safeguarding ofnitrate accumulations; (2) the production of humus, and (3) a combinationof both.
THE SAFEGUARDING OF NITRATE ACCUMULATIONS
In studying this important matter we must at the outset consider howNature, if left to herself, always deals with the nitrates prepared fromorganic matter by the micro-organisms in the soil. They are never allowedto run to waste but are immobilized by plants including the film of algaein the surface soil. These latter are easily decomposed: they aretherefore exceedingly valuable agencies for safeguarding nitrates.
The farmer has at his command two methods of nitrate immobilization. Hecan either intercept his surplus nitrate accumulations by sowing aleguminous crop or by managing his weeds and soil algae so that they dothe same thing automatically. In either case nitrates which wouldotherwise run to waste are converted into young fresh growth which cannotthen be lost by leaching and which later on can be rapidly converted backinto available nitrogen and minerals by the organisms in the soil.Obviously if weeds can be managed so that all nitrate accumulations canbe utilized and the resulting growth can be turned under and decomposedin time for the next crop, there is no need to sow a leguminous crop todo what Nature herself can do so much better.
One of the best examples I have seen of the combined use of weeds andcatch crops for immobilizing nitrates was worked out by Mr. L. P. Hayneson the large hop garden of Messrs. Arthur Guinness, Son & Co. at Bodiamin Sussex. Surface cultivation in this garden ceases in August soon afterthe hops form. A little mustard is then sown which, with the chickweed,soon produces a green carpet without interfering with the ripening of thehops. At picking time the mixed seedlings are well established, afterwhich they have the nitrates formed at the end of the summer and in earlyautumn entirely to themselves. Growth is very rapid. During the autumnsheep are brought in to graze the mustard. Their urine and dung fall onthe chick-weed and so contribute a portion of the essential animalwastes. In the spring the easily decomposed chickweed is ploughed intothe fertile soil and decayed in good time for the next crop of hops. Thesoil of this hop garden is now heavily charged with chickweed seeds sothat the moment surface cultivation is stopped the following August a newcrop starts. This management of a common weed of fertile soil to fit inwith the needs of the hop appeared to me to be nothing short of a strokeof genius. It would be difficult to find a more efficient green-manurecrop than the one Nature has provided for nothing. Could there be abetter example of the use of a fertility reserve for rapidly decomposinga green crop in the early spring? The ground at Bodiam is hardly everuncovered; it is occupied either by hops or by chickweed; one cropdovetails into the other; the energy of sunlight is almost completelyutilized throughout the year; the invisible labour force of the hopgarden--earthworms and micro-organisms--is kept fully occupied. As theuse of artificials and poison sprays is reduced, there will be acorresponding increase in efficiency in this section of the unseenestablishment.
Much more use might be made of this method of green-manuring incountries like Great Britain. In fruit, vegetable, and potato growingparticularly, there seems no reason why an autumn crop of weeds shouldnot be treated as green-manure on Bodiam lines. If the land is in goodheart, the soil will have no difficulty in decaying the weeds. If theland is poor in organic matter, a dressing of freshly prepared humus ofnot less than 5 tons to the acre should be spread on the weeds beforethey are turned under.
THE PRODUCTION OF HUMUS
The production of humus, by means of a green-manure crop, is a much moredifficult matter than the use of this method for immobilizing nitrates.Nevertheless, it is of supreme importance in the maintenance of soilfertility. The factors involved in the transformation of green-manureinto humus in the soil are the same as those in the compost heap. Allfactors must operate together. Failure of one will upset the processentirely. If this occurs the next crop will be sown in soil which hasbeen placed in an impossible condition. The land will be called upon tocomplete the formation of humus and to grow a crop at the same time. Thisis asking too much. The soil will take up its interrupted task andproceed with the manufacture of humus. It will neglect the crop. Theuncontrollable factor is the rainfall. It must be just right if humusmanufacture in the soil is to succeed. In India, for example, during anexperience of twenty-six years it used to be just right about once in sixor seven years. It was completely wrong in the remainder. Often there wastoo much rain after ploughing in, when the aerobic phase never developedand bog conditions were established instead. At other times there wasinsufficient rain for the early fungous stage. Where, however, irrigationis available, any shortage of the Indian monsoon makes no difference.
In exceptional cases, however, it is possible to carry on the manufactureof humus in the soil without any risk of temporary failure. One Britishexample may be quoted. On some of the large farms in the Holland Divisionof Lincolnshire peas are grown as a rotation crop with potatoes. Theproblem is to manufacture humus before the next crop of potatoes isplanted. This has been solved. Early in July the peas are cut and carriedto the shelling machines where the green seeds are separated and largequantities of crushed haulm are left. Immediately after the removal ofthe peas the land is sown with beans. The crushed pea haulm is thenscattered on the surface of the newly sown land followed by a lightdressing of farm-yard manure--about 6 or 7 tons to the acre. The beansgrow through the fermenting layer on the surface of the soil and help tokeep it moist. While the beans are growing humus is being manufactured ina thin sheet all over the field. At the end of September, when the beansare in flower, this sheet composting on the ground is complete. The greencrop is then lightly ploughed in together with a layer of freshlyprepared compost. Humus manufacture is then continued in the soil. Thebeans under these conditions decay quickly; the process of humusmanufacture is completed before the planting of the next potato crop.
THE SAFEGUARDING OF NITRATES FOLLOWED BY THE MANUFACTURE OF HUMUS
The immobilization of nitrates by means of a green crop followed by theconversion of the green-manure into humus needs time and complete controlof all the operations. An example of the successful use of this method isdescribed in Chapter XIV. Heavy crops of sugar-cane were produced atShahjahanpur in the United Provinces by intercepting the nitratesaccumulated at the break of the south-west monsoon by means of aleguminous crop and then converting this into humus with the assistanceof the autumn accumulation of nitrate in the same soil.
It follows from the principles underlying green-manuring and theapplications of these principles to agricultural practice that theploughing in of a green crop is not a simple question of the addition ofso many pounds of nitrogen to the acre but a vast and many-sidedbiological problem. Moreover it is dynamic, not static; the agentsinvolved are alive; their activities must fit in with one another, withagricultural practice on the one hand and with the season on the other.If we attempt to solve such a complex on the basis of mere nitrogencontent or on that of carbon: nitrogen ratios, we are certain to runcounter to great biological principles and come into conflict with onerule in Nature after another. It is little wonder, therefore, thatgreen-manuring has led to so much misunderstanding and to so muchdisappointment.
THE REFORM OF GREEN-MANURING
The uncertainties of humus manufacture in the soil can be overcome bygrowing the green crop to provide material for composting. This of courseadds to the labour and the expense, but in many countries it is proving acommercial proposition. In Rhodesia, for example, crops of salt hemp arenow regularly grown to provide litter, rich in nitrogen, for mixing withmaize stalks so as to improve the carbon: nitrogen ratio of the beddingused in the cattle kraals. In this way the burden on the soil is greatlyreduced; it is only called upon to decay what is left of the root systemof the green crop at harvest time. Humus manufacture is shared betweenthe soil and the compost heap.
In converting materials low in nitrogen (such as sugar-cane leaves andcotton stalks) into humus it is an immense advantage to mix theserefractory materials with some leguminous plant in the green state. Themanufacture of humus is speeded up and simplified; the amount of waterneeded is reduced; the land on which the green crop was raised benefits.
CLARKE, G. 'Some Aspects of Soil Improvement in relation to CropProduction', Proc. of the Seventeenth IndianScience Congress, Asiatic Society of Bengal, Calcutta, 1930, p. 23.
WAKSMAN, S. A., and TENNEY, F. G. Composition of Natural Organic Materialsand their Decomposition in the Soil,Soil Science, xxiv, 1927, p. 275; xxviii, 1929, p. 55; and xxx,1930, p. 143.
DEVELOPMENTS OF THE INDORE PROCESS
Two very different methods of approach to the problems of grass-landmanagement in a country like Great Britain are possible. We can eitherstudy the question from the point of view of the present organization ofagricultural research in this country or we can bring the world-wideexperience of the grass and clover families to bear as if no institutionslike the Welsh Plant Breeding Station, the Rowett Institute at Aberdeen,or the Rothamsted Experiment Station--all of which deal independentlywith some fragment of the grass-land problem--had ever been contemplated.As the advantages of the fresh eye are many and obvious and as the writerhas had a long and extensive first-hand experience of the cultivation ofa number of crops belonging to the grass and clover families, theprinciples underlying grass-land management in Great Britain will beconsidered from a new angle, namely, the conditions which practicalexperience in the tropics has shown to be necessary for grasses andlegumes to express themselves and to tell their own story.
The grass and clover families are widely distributed and cultivated allover the world--from the tropics to the temperate zones and at allelevations and under every possible set of soil and moistureconditions--either as separate crops or more often mixed together.Everywhere the equivalent of the short ley, composed of grasses andlegumes, is to be found. The successful mixed cultivation of these twogroups of plants has been in operation for many centuries: in the Orientthey were grown together in suitable combinations long before Englandemerged from the primitive condition in which the Roman invaders foundit--an island covered for the most part with dense forests and impassablebogs.
What are the essential requirements of the grass and clover families?The clearest answer to this question is supplied by tropical agriculture;here the growth factors impress themselves on the plant much moredefinitely and dramatically than they do in a damp temperate island likeGreat Britain where all such reactions are apt to be very much toned downand even blurred.
Sugar-cane, maize, millets, and the dub grass of India (Cynodon dactylonPers.) are perhaps the most widely cultivated and the most suitablegrasses for this study. Lucerne, san hemp (Crotalaria juncea L.), thecluster bean (Cyamopsis psoralioides D.C.), and the pigeon pea (Cajanusindices Spreng.) are corresponding examples of the clover family. Thelast two of these are almost always grown mixed either with millets ormaize, very much in the same way as red clover and rye-grass are sowntogether in Great Britain.
The grass family must first be considered. A detailed account of thecultivation of the sugar-cane will be found in a later chapter. Humus andample soil aeration, combined with new varieties which suit the improvedsoil conditions, enable this grass to thrive, to resist disease, and toproduce maximum yields and high quality juice without any impoverishmentof the soil. Maize behaves in the same way and is perhaps one of our bestsoil analysts. Any one who attempts to grow this crop without organicmatter will begin to understand how vital soil fertility is for the grassfamily. The requirements of the dub grass in India, one of the mostimportant fodder plants of the tropics, are frequent cultivation andabundance of humus. The response of this species to a combination ofhumus and soil aeration is even more remarkable than in maize: once thesefactors are in defect growth stops. The behaviour of dub grass, as willbe seen later on, indicates clearly what all grasses the world over need.
Any one who grows lucerne in India under irrigation will court certainfailure unless steps are taken to keep the crop constantly supplied withfarm-yard manure and the aeration of the surface soil at a high level.When suitable soil conditions are maintained it is possible to harvesttwenty or more good crops a year. Once the surface soil is allowed topack and regular manuring is stopped, a very different result isobserved. The number of cuts falls off to three or four a year and thestand rapidly deteriorates. When san hemp is grown for green-manuring orfor seed in India satisfactory results are only obtained if the crop ismanured with cattle manure or humus. These two leguminous crops do notstand alone. Every member of this group I have grown responds at once tofarmyard manure or humus. But all this is not in accordance with theory.
According to the text-books the nodules in the roots of leguminous plantsshould be relied on to furnish combined nitrogen and this group shouldnot need nitrogenous manure. Practical experience and theory are so wideapart as to suggest that some other factor must be in operation. It wasnot till January 1938 that I discovered what this factor was. On theWaldemar tea estate in Ceylon I saw a remarkable crop of a green-manureplant--Crotalaria anagyroides--growing in soil rich in humus. The rootdevelopment was exceptional: an examination of the active roots showedthat they were heavily infected with mycorrhiza. Other tropicalleguminous plants growing in similar soils also exhibited the mycorrhizalassociation. So did several species of clover collected in France andGreat Britain. These results at once suggested the reason why san hemp,lucerne, and many other tropical legumes respond so strikingly to cattlemanure. They must all be mycorrhiza-formers.
The fact that leguminous plants and grasses respond to the same factorsand that the former group are mycorrhiza-formers suggested that thisassociation would also be found in the grasses. Sugar-cane was firstinvestigated. It proved to be a mycorrhiza-former. The grasses of themeadows and pastures of France and Great Britain were then studied. Theherbage of the celebrated meadows of La Frau, between Salon and Arles inProvence, was examined for mycorrhiza in 1938 and again in 1939. In bothseasons the roots of the grasses were found to be infected withmycorrhiza. Dr. Levisohn's report on the samples collected in July 1939reads as follows: 'Sporadic but deep infection of the long and shortroots: coarse mycelium inter-and intra-cellular: digestion stages: theproducts of digestion seem to be translocated rapidly.' In the materialfrom La Crau examined in 1939 the most remarkable example of themycorrhizal relationship occurred in a species of Taraxacum which formedat least a quarter of the herbage. Here the infection of the inner layersof the long and short roots was 'very widespread and deep. The myceliumis of large diameter, thin-walled with granular contents. Distributionmainly intra-cellular. Digestion showing all stages of disintegration.Root hairs sparsely formed. The mycorrhizal regions of the roots areindicated macroscopically by beading, greater opacity, and slightyellowing of the infected zones' (Levisohn). This suggests that some orall of the so-called weeds of grass-land may well play an important rolein the transmission of quality from soil to plant and in the nutrition ofthe animal. Samples of the turf from two well-known farms in England--Mr.Hosier's land in Wiltshire and Mr. William Kilvert's pastures in CorveDale in Shropshire--were then examined. They gave similar results tothose of La Crau. Clearly the grass family, like the clover group, aremycorrhiza-formers, a fact which at once explains why both these classesof plants respond so markedly to humus.
This independent approach to the grass-land problems of countries likeGreat Britain has brought out new principles. Grasses and clovers fallinto one group as regards nutrition and not, as hitherto thought, intotwo groups. Both require the same things--humus and soil aeration. Bothare connected with the organic matter in the soil by a living fungousbridge which provides the key to their correct nutrition and therefore tothe management of grass-land. If this view is a sound one it follows thatany agency which will increase the natural formation of humus under theturf of our grass-lands will be followed by an improvement in the herbageand by an increase in their stock-carrying capacity. The methods whichincrease humus formation in the soil must now be considered. Thefollowing may be mentioned:
1. The bail system. The most spectacular example of humus manufacture inthe soil underneath a pasture is that to be seen on Mr. Hosier's land onthe downs near Marlborough. By a stroke of the pen, as it were, heabolished the farm-yard, the cowshed, and the dung-cart in order tocounter the fall in prices which followed the Great War. He reacted toadversity in the correct manner: he found it a valuable stimulant inbreaking new ground. The cows were fed and made to live out of doors.They were milked in movable bails. Their urine and dung weresystematically distributed at little cost over these derelict pastures.The vegetable residues of the herbage came in contact with urine, dung,air, water, and bases. The stage was set for the Indore Process. Mr.Hosier's invisible labour force came into action: the micro-organisms inthe soil manufactured a sheet of humus all over the downs: the earthwormsdistributed it. The roots of the grasses and clovers were soon geared upwith this humus by means of the mycorrhizal association. The herbageimproved; the stock-carrying capacity of the fields went up by leaps andbounds. Soil fertility accumulated; every five years or so it was cashedin by two or three straw crops; another period under grass followed, andso on. Incidentally the health of the animals also benefited; theprognostications of the neighbourhood (when this audacious innovationstarted) that the cows and heifers would soon perish through tuberculosisand other diseases have not been fulfilled. (Mr. Hosier has done morethan solve a local problem and provide evidence in support of a newtheory. His work has drawn attention to the potential value of ourdownlands--areas which in Roman and Saxon times supported a largeproportion of the population of Great Britain.)
2. The use of basic slag. On many of the heavy soils under grass thelimiting factor in humus production is not urine but oxygen. Everythingexcept air is there in abundance for making humus--vegetable and animalwastes as well as moisture. Under such turf the land always suffers fromasphyxiation. The soil dies. This is indicated by the absence of nitratesunder such turf. About fifty years ago it was discovered that suchpastures could be improved by dressings of basic slag. As this materialcontains phosphate, and as its use stimulates the clovers, it was assumedthat these soils suffered from phosphatic depletion as a result offeeding a constant succession of live stock, each generation of whichremoves so many pounds of phosphate in their bones. When, however, weexamine the turf of a slagged pasture we find that humus formation hastaken place. If the application of slag is repeated on these heavy landsafter an interval of five or six years there is often no furtherresponse. When we apply basic slag to pastures on the chalk there is noresult. There is phosphate depletion on strong lands only at one point;none at all on light chalk downs. These results do not hold together;indeed they contradict one another. Are we really dealing with phosphatedeficiency in these lands? May not the humus formed after slag is addedexplain the permanent benefit of this manuring? May it not prove that theeffect of slag on heavy soils has been in the first instance a physicalone which has improved the aeration, reduced the acidity, and so helpedhumus manufacture to start? We can begin to answer these questions bystudying what happens when the aeration of heavy grass-land is improvedby an alternative method--subsoiling.
3. Sub-soiling. The effect of sub-soiling heavy grasslands wasdescribed by Sir Bernard Greenwell, Bt. in a paper read to the Farmers'Club on January 30th, 1939, in the following words:
'Taking our grass-land first, probably more can be done by propermechanical treatment followed by intensive stocking than by artificialmanuring. Some people are suggesting that we should plough up a lot ofour second-rate pasture land and re-sow it, but this I have found is veryspeculative as the cost is in the neighbourhood of 3 to 5 pounds an acreand the results are bound to be uncertain. By cleaning out ditches,reopening drains and by mole draining, however, a lot can be done. I havealso found that by using a Ransome mole plough or sub-soiler of the wheeltype, pulled through the land at a depth of 12 inches to 14 inches, 4feet apart, one can produce much better grass, and this is proved by thegreatest expert of all--the animal. In a field which was partlysub-soiled we found that this sub-soiled part was grazed hard by thecattle, and the part that was not treated in this way was only lightlypicked over. The cost of this is about 2s. 6d. per acre without overheadsand lost time. We reckon 1 pound a day for a 40-h.p. tractor, includinglabour, depreciation, etc., and a tractor will do 9 to 1O acres a daysub-soiling at 4 feet intervals.'
Poor aeration was obviously the limiting factor at Marden Park. Once thiswas removed humus formation started and the herbage improved. It will beinteresting to watch the results of the next stage of this work. Half ofa sub-soiled field has been dressed with basic slag and the reaction ofthe animals is being watched. If they graze the field equally, basic slagis probably having no effect: if the animals prefer the slagged half thenthis manure is required. (The Marden Park results suggest a furtherquestion. Will sub-soiling at 2s. 6d. an acre replace the ploughing-upcampaign recently launched by the Ministry of Agriculture for which theState pays 2 pounds an acre? If, as seems likely, the basic slag andploughing-up subsidies are both unnecessary, a large sum of money will beavailable for increasing the humus of the soils of Great Britain, theneed for which requires no argument.)
4. The cultivation of grass-land. One of the recommendations of the WelshPlant Breeding Station is the partial or complete cultivation ofgrass-land. Partial cultivation is done from the surface by various typesof harrow: complete cultivation by the plough. In both cases aeration isimproved; the production of humus is stimulated; generally speaking theresult obtained is in direct proportion to the degree of cultivation;ploughingup and reseeding is far better for the grass than merescarification with harrows. In this work we must carefully distinguishthe means and the end. The agency is some form of cultivation; theconsequence is always the manufacture of humus.
It will be evident that the various methods by which humus ismanufactured under the growing turf itself or by ploughing up and rottingthe old turf agree in all respects with what is to be learned from thegrasses and the legumes of the tropics. Sir George Stapledon's advice asregards Great Britain is supported by the age-long experience of theagriculture of the East. No stronger backing than this is possible. Thereis only one grass-land problem in the world. It is a simple one. The soilmust be brought back to active life. The micro-organisms and earthwormsmust be supplied with freshly made humus and with air. Varieties ofgrasses and legumes which respond to improved soil conditions must thenbe provided. In this way only can the farmers of Great Britain make themost of our green carpet. Our grass-lands will then be able to do whatNature does in the forest--manure themselves.
The order in which improvements should be introduced in grass-landmanagement is important. Soil fertility must first be increased so thatthe grasses and clovers can fully express themselves. Improved varietiesshould then be selected to suit the new soil conditions. If we study thevariety by itself without any reference to the soil and develop higheryielding strains of grasses and clovers for the land as it is now, thereis a danger, indeed almost a certainty, that the farmer will be furnishedwith yet another means of exhausting his soil. The new varieties willhave a short life: they will prove to be a boomerang: the last state ofthe farm will be worse than the first. If, however, the soil conditionsare first improved and the system of farming is such that soil fertilityis maintained, the plant breeder will be provided with a safe field forhis activities. His work will then have a permanent value.
How are we to test the fertility of grass-land? Mr. Hosier has suppliedthe answer. Grass-land can be tested for fertility by means of a completeartificial manure. If the soil is really fertile, such a dressing willgive no result, because no limiting factor in the shape of shortage ofnitrogen, phosphorus, or potash exists. Mr. Hosier has summed up hisexperience of this matter in a letter dated Marlborough, April 6th, 1938,as follows:
'On my improved grass-land, I have on several occasions put downexperimental plots of artificial manures and there was no response evenwhere there Divas a complete fertilizer applied. Before I startedopen-air dairying on a big scale in 1924, I put down 150 plots and inmany places I could write my name with artificials.'
The value of this experience does not end with the testing of soilfertility. It indicates the very high proportion of the grasslands ofwestern Europe which are infertile and which need large volumes of humusto restore their fertility. Most of the fields under grass will respondto artificials. All these are infertile.
The consequences of the improvement of grass-land in a country like GreatBritain can now be summarized. The land will carry more live stock. Thesurplus summer grass can be dried for winter feeding. The storedfertility in the pastures can be cashed in at any time in the form ofwheat or other cereals. A valuable food reserve in time of war willalways be available. As Mr. Hosier has shown, there will be no damagefrom wireworms when such fertile pastures are broken up and sown withwheat.
GREENWELL, SIR BERNARD. Soil Fertility: The Farm's Capital, Journalof the Farmers Club, 1939, p. 1.
HOSIER, A. J. 'Open-air Dairying', Journal of the Farmers' Club,1927, p. 103.
HOWARD, A. Crop Production in India: A Critical Survey of its Problems,Oxford University Press, 1924.
STAPLEDON, R. G. The Land, Now and To-morrow, London, 1935.
DEVELOPMENTS OF THE INDORE PROCESS
THE UTILIZATION OF TOWN WASTES
The human population, for the most part concentrated in towns andvillages, is maintained almost exclusively by the land. Apart from theharvest of the sea, agriculture provides the food of the people and therequirements of vegetable and animal origin needed by the factories ofthe urban areas. It follows that a large portion of the waste products offarming must be found in the towns and away from the fields whichproduced them. One of the consequences, therefore, of the concentrationof the human population in small areas has been to separate, often byconsiderable distances, an important portion of the wastes of agriculturefrom the land. These wastes fall into two distinct groups:
(a) Town wastes consisting mainly of the contents of the dustbins,market, street, and trade wastes with a small amount of animal manure.
(b) The urine and faeces of the population.
In practically all cases in this country both groups of waste materialsare treated as something to be got rid of as quickly, asunostentatiously, and as cheaply as possible. In Great Britain most townwastes are either buried in a controlled tip or burnt in an incinerator.Practically none of our urban waste finds its way back to the land. Thewastes of the population, in most Western countries, are first dilutedwith large volumes of water and then after varying amounts ofpurlfication, are discharged either into rivers or into the sea. Beyond alittle of the resulting sewage sludge the residues of the population areentirely lost to agriculture.
From the point of view of farming the towns have become parasites. Theywill last under the present system only as long as the earth's fertilitylasts. Then the whole fabric of our civilization must collapse.
In considering how this unsatisfactory state of affairs can be remediedand how the wastes of urban areas can be restored to the soil, themagnitude of the problem and the difficulties which have to be overcomemust be realized from the outset. These difficulties are of two kinds:those which belong to the subject proper, and those inherent inourselves. The present system of sewage disposal has been the growth of ahundred years; problem after problem has had to be solved as it arosefrom the sole point of view of what seemed best for the town at themoment; mother earth has had few or no representatives on municipalcouncils to plead her cause; the disposal of waste has always been lookedupon as the sole business of the town rather than something whichconcerns the well-being of the nation as a whole. The fragmentation ofthe subject into its urban components--medical, engineering,administrative, and financial--has followed; direction has been lost. Thepiecemeal consideration of such a matter could only lead to failure.
Can anything be done at this late hour by way of reform? Can mother earthsecure even a partial restitution of her manurial rights? If the easiestroad is first taken a great deal can be accomplished in a few years. Theproblem of getting the town wastes back into the land is not difficult.The task of demonstrating a working alternative to water-borne sewage andgetting it adopted in practice is, however, stupendous. At the moment itis altogether outside the bounds of practical politics. Some catastrophe,such as a universal shortage of food followed by famine, or the necessityof spreading the urban population about the country-side to safeguard itfrom direct and indirect damage by hostile aircraft, will have to be uponus before such a question can even be considered.
The effective disposal of town wastes is, however, far less difficult, aswill be seen by what has already been accomplished in this country.Passing over the earlier experiments with town wastes, summed up in arecent publication of the Ministry of Agriculture (Manures and Manuring,Bulletin 36, Ministry of Agriculture and Fisheries, H.M. StationeryOffice, 1937), in which the dustbin refuse was used without modification,the recent results obtained with pulverized wastes, prepared by passingthe sorted material (to remove tin cans, bottles, and other refractoryobjects) through a hammer mill, point clearly to the true role of thismaterial in agriculture. Its value lies, not in its chemical composition,which is almost negligible, but in the fact that it is a perfect diluentfor the manure heap, the weakest link in agriculture in many countries.The ordinary manure heap on a farm is biologically unbalanced andchemically unstable. It is unbalanced because the micro-organisms whichare trying to synthesize humus have far too much urine and dung and fartoo little cellulose and lignin and insufficient air to begin with. It isunstable because it cannot hold itself together; the valuable nitrogen islost either as ammonia or as free nitrogen; the micro-organisms cannotuse up the urine fast enough before it runs to waste; the proteins areused as a source of oxygen with the liberation of free nitrogen. Thefungi and bacteria of the manure heap are working under impossibleconditions. They live a life of constant frustration which can only beavoided by giving them a balanced ration. This can be achieved bydiluting the existing manure heaps with three volumes of pulverized townwastes. The micro-organisms are then provided with all the cellulose andlignin they need. The dilution of the manure heap automatically improvesthe aeration. The volume of the resulting manure is multiplied by atleast three; its efficiency is also increased.
Such a reform of the manure heap is practicable. Two examples may bequoted. At the large hop garden at Bodiam in Sussex, the property ofMessrs. Arthur Guinness, Son & Co., Ltd., over 30 tons of pulverized townwastes from Southwark are used daily throughout the year for humusmanufacture. This material is railed in 6-ton truck-loads to Bodiam,transferred to the hop gardens by lorry and then composted with all thewastes of the garden--hop vine, hop string, hedge and roadside trimmings,old straw, all the farm-yard manure which is available--and every othervegetable and animal waste that can be collected locally. The annualoutput of finished humus is over 10,000 tons, which is prepared at anall-in cost of 10s. a ton, including spreading on the land. The Managerof this garden, Mr. L. P. Haynes, has worked out comparative figures ofcost between nitrogen, phosphorus, and potash applied in the form ofhumus or artificials. The cost of town wastes for Bodiam is 4s. 6d. aton; lorry transport from rail to garden 3s. a ton; assembling andturning the compost heaps and spreading on the land 2s. 6d. a ton. Theanalysis of this humus was: 0.96 per cent. nitrogen, 2.45 per cent.phosphate, and 0.62 per cent. potash. Sixteen tons of humus thereforecontain 344 lb. of nitrogen, 769 lb. of P2O5, and 222 lb. of K2O. Thecost of this at 10s. a ton including spreading comes to 8 pounds an acre.The purchase, haulage, and sowing of these amounts of NPK in the form ofsulphate of ammonia, basic slag, and muriate of potash comes to 9 pounds12s. 7-1/2d. There is therefore a distinct saving when humus is used.This, however, is only a minor item on the credit side. The texture of thesoil is rapidly improving, soil fertility is being built up, the need forchemical manures and poison sprays to control pests is becoming less.
The manurial policy adopted on this hop garden has been confirmed inrather an interesting fashion. Before a serious attempt was made toprepare humus on the present scale, a small amount of pulverizedSouthwark refuse had been in use. The bulk of the manure used, however,was artificials supplemented by the various organic manures andfertilizers on the market. The labourers employed at Bodiam weretherefore conversant with practically every type of inorganic and organicmanure. One of their privileges is a supply of manure for their gardens.They have always selected pulverized town wastes because they considerthis grows the best vegetables.
A second large-scale demonstration of the benefits which follow thereform of the manure heap has been carried out at Marden Park in Surrey.Many thousands of tons of humus have been made by composting pulverizedtown wastes with ordinary dung. In a paper read to the Farmers' Club onJanuary 30th, 1939, Sir Bernard Greenwell refers to these results asfollows: 'I have only two years' experience of this myself, but from theresults I have seen we can multiply our dung by four and get crops asgood as if the land had been manured with pure dung.' In 1938 I saw someof this work. Many of the fields on the estate had been divided intohalf, one portion being manured with humus and the other with an equalnumber of cartloads of dung. I inspected a number of these fields just asthe corn was coming into ear. In every case the crops grown withhumus--wheat, beans, oats, clover, and so forth--were definitely betterthan those raised with farm-yard manure. These results showed that thisland wants freshly prepared humus, not so many lb. to the acre of thisand that. In manuring we are nourishing a complex biological system notministering to the needs of a conveyor belt in a factory.
Once the correct use of Southwark wastes was demonstrated a demand forthis material arose. The sales increased; the demand now exceeds thesupply. The details are given in Table 7.
Sales of crushed wastes at Southwark
Year Tons crushed* Tons sold Income from sales1933-4 18,643 +12 cwt. 7,971 + 9 cwt. 653/9s/9d1934-5 18,620 + 1 cwt. 6,341 + 9 cwt. 482/2s/7d1935-6 19,153 + 14 cwt. 9,878 + 5 cwt. 1,001/11s/1d1936-7 18,356 + 13 cwt. 12,760 + 15 cwt. 1845/6s/8d1937-8 18,545 + 15 cwt. 15,391 + 8 cwt. 2,306/13s/7d1938-9 17,966 + 3 cwt. 17,052 + 1 cwt. 2,715/14s/8d
* A certain amount of these wastes is required by the Depot itselffor sealing one of its own tips; so it is not possible to sellall the waste crushed to farmers.
When it is remembered that the annual dustbin refuse in Great Britain isin the neighbourhood of 13,000,000 tons and that about half of thismaterial can be used for making the most of the urine and dung of ourlive stock, it will be evident what enormous possibilities exist forraising the fertility of the zones of land within, say, fifty miles ofthe large cities and towns. A perusal of the Public Cleansing Return forthe year ending March 31st, 1938, published by the Ministry of Health,shows that a certain proportion of this dustbin refuse is still burnt inincinerators. Once, however, the agricultural value of this material isrealized by farmers and market gardeners it will not be long beforeincineration is given up and the whole of the organic matter in our townwastes finds its way into the manure heap. When this time comes theutilization of the enormous dumps of similar wastes, which accumulatedbefore controlled tipping was adopted, can be taken in hand. Thesecontain many more millions of tons of material which can be dealt with onSouthwark lines. In this way the manure heaps of a very large portion ofrural England can be reformed and the fertility of a considerable arearestored. A good beginning will then have been made in the restitution ofthe manurial rights owing to the country-side. The towns will have begunto repay their debt to the soil.
Besides the wastes of the dustbins and the dumps there is another andeven more important source of unused humus in the neighbourhood of ourcities and towns. This occurs in the controlled tips in which most of thedustbin refuse is now buried. In controlled tipping the town wastes aredeposited in suitable areas near cities and sealed with a layer of clay,soil, or ashes so as to prevent nuisance generally and also the breedingof flies. The seal, however, permits sufficient aeration for the firststage in the conversion of most of the organic matter into humus. Theresult is that in a year or two the tip becomes a humus mine. The crudeorganic matter in these wastes is slowly transformed by means of fungiand bacteria into humus. All that is needed is to separate the finelydivided humus from the refractory material and to apply it to the land.
A very valuable piece of research work on this matter has recently beenundertaken at Manchester. The results are described by Messrs. Jones andOwen in Some Notes on the Scientific Aspects of Controlled Tipping,published by the City of Manchester. The main object of the work was toestablish the facts underlying controlled tipping so that any discussionon the efficacy of this process, as compared with incineration, could beconducted on the basis of carefully ascertained knowledge. Theinvestigation, however, is invaluable from the agricultural standpoint.The experiments were begun in August 1932 at Wythenshawe in a controlledtip on a piece of low-lying marshy ground subject to periodic floodingfrom the adjacent river Mersey. One of the subsidiary objects of thetipping was to reclaim the land for recreational or other uses in thefuture. Six experimental plots were selected for the tests, eachapproximately 16 feet by 12 feet. The material contained in the tip wasordinary dustbin refuse tipped to a depth of 6 feet. The first object wasto ascertain the consequences of bacterial action on the organic matterin the interior of the tip, such as the generation of temperature, thebiological as well as the chemical changes, and any alteration in thegaseous atmosphere in the interior of the mass. Having disposed of thesepreliminary matters, it was proposed to attack the main problem and toanswer the question: Is controlled tipping safe?
Careful attention was first given to the seal. The surface of the plotswas covered with a layer of fine dust and ashes, of a minimum thicknessof 6 inches, obtained by passing household refuse over a 3/8 inch mesh.Such a seal, which contained about 2.5 per cent. of organic matter,proved to be a suitable mechanical covering and also prevented thebreeding of flies. The sides and ends of the experimental plots werecovered with clay well tamped down. The plots therefore behaved as ifthey were large flowerpots in direct contact with the moist earth belowbut separated from the outer atmosphere by a permeable seal of screeneddust and fine ashes.
The unsorted household refuse under experiment represented an averagesample and contained about 42 per cent. of organic matter, the remaining58 per cent. being composed of inorganic materials. After tipping andsealing, there was a rapid rise of temperature, irrespective of theseason, to a maximum of 160 degrees F. towards the end of the first week.This was caused by the activities of the thermogenic and thermophyllicmembers of the aerobic group of bacteria which break down cellulose,liberate heat, and produce large volumes of carbon dioxide. At the sametime these organisms rapidly multiply and in so doing synthesize largeamounts of protein from the mixed wastes. This on the death of theorganisms forms a valuable constituent of the humus left when thebacterial activities die down after about fifteen weeks, as is indicatedby the return of the temperature of the tip to normal. The controlled tiptherefore behaves very much like an Indore compost heap.
As would be expected from the heterogeneous nature and unevendistribution of the contents of the tip, considerable variations wereshown in the maximum temperatures attained. During the period offermentation the bacterial flora (at first aerobic) use and reduce theoxygen content of the tip, and so pave the way for the facultativeanaerobic organisms which complete the conversion of the organic matterinto humus.
A detailed examination of the gases produced in the tips showed that inaddition to nitrogen, carbon dioxide, and oxygen, a considerable quantityof methane (16 per cent.) and smaller proportions of carbon monoxide (2.8per cent.) and hydrogen (2.5 per cent.) occurred. Traces only ofsulphuretted hydrogen were detected. The presence of carbon monoxide,methane, and hydrogen would naturally result from the anaerobicfermentation which establishes itself in the second stage of theproduction of humus after the free oxygen in the tip becomes exhausted.These gases are similar to those produced by the decay of organic matterin swamp rice cultivation in India, where the supply of oxygen is almostalways in defect. The absence of anything beyond a trace of sulphurettedhydrogen is reassuring, as this proves that the intense reduction whichprecedes the formation of the salts of alkali soils does not occur in acontrolled tip.
The manurial value of the humus in the tips was determined by analysisand valuation. The average content of nitrogen was 0.8 per cent., ofphosphoric acid 0.5 per cent., of potash 0.3 per cent. The estimatedvalue of the dry material per ton was 10s. This value, however, will haveto be multiplied by a factor ranging from 2 to 2.5, because experiencehas shown that the market price of organic manures, based on supply anddemand, is anything from two to two and a half times greater than thatcalculated from the chemical analysis. The unit system of valuationapplies only to artificial manures like sulphate of ammonia made infactories; it does not hold in the case of natural manures like humus.
One of the last sections of the Report relates to the danger ofinfectious diseases as a possible consequence of controlled tipping. Theauthors conclude that 'danger arising from possible presence ofpathogenic germs in a controlled tip may be dismissed as nonexistent'.
One of the plots, No. 1, not only developed a high temperature but showeda much more gradual fall than the other plots. This was apparently due tothe higher content of organic matter combined with better aeration. Theresults of this plot suggest that more and better humus might be obtainedin a controlled tip if the object of tipping were, as it should be, tosecure the largest amount of humus of the best possible quality. It wouldnot be a difficult matter to increase the oxygen intake at the beginningby allowing more and more air to diffuse in from the atmosphere. Thiscould perhaps be done most easily and cheaply by reducing the thicknessof the seal by about a third. If the seal were reduced in this way, ampleair would find its way into the fermenting mass in the early stages; thehumus would be improved; the covering material saved could be used for anew seal. The controlled tip would then become a very efficient humusfactory.
In countries where there is no system of water-borne sewage there hasbeen no difficulty in converting the wastes of the population into humus.The first trials of the Indore Process for this purpose were completed inCentral India in 1933 by Messrs. Jackson and Wad at three centres nearIndore--the Indore Residency, Indore City, and the Malwa Bhil Corps.Their results were soon taken up by a number of the Central India andRajputana States and by some of the municipalities in India. Subsequentdevelopments of this work, including working drawings and figures ofcost, were summed up in a paper read to the Health Congress of the RoyalSanitary Institute held at Portsmouth in 1938. This document has beenreproduced as Appendix C. A perusal of this statement shows that humanwastes are an even better activator than animal residues. All that isnecessary is to provide for abundant aeration in the early stages and tosee that the night soil is spread in a thin film over the town wastes andthat no pockets or definite layers are left. Both of these interfere withaeration, produce smell, and attract flies. Smell and flies are thereforea very useful means of control. If the work is properly done there is nosmell, and flies are not attracted because the intense oxidationprocesses involved in the early stages of the synthesis of humus are setin motion. It is only when the air supply is cut off at this stage thatputrefactive changes occur which produce nuisance and encourage flies.
Whether or not it will always be necessary to erect permanentinstallations for converting night soil and town refuse into humus,experience only can decide. In a number of cases it may be easier to dothe composting daily in suitable pits or trenches on the lines describedin Appendix C. In this way the pits or trenches themselves becometemporary composting chambers; no turning is required; the line of pitsor trenches can soon be used for agricultural purposes--for growing allkings of fodder, cereal, and vegetable crops. At the same time the landis left in a high state of fertility.
A number of medical officers all over the world are trying out thecomposting of night soil on the lines suggested. In a few years a greatdeal of experience will be available, on which the projects of the futurecan be based.
As far as countries like Great Britain are concerned, the only openingsfor the composting of night soil occur in the countryside and in theouter urban zones where the houses are provided with kitchen gardens. Insuch areas the vast quantities of humus in the controlled tips can beused in earth-closets and the mixed night soil and humus can be lightlyburied in the gardens on the lines so successfully carried out by thelate Dr. Poore and described in his Rural Hygiene, the second edition ofwhich was published in 1894.
Since Dr. Poore's work appeared a new development in housing has takenplace in the garden cities and in colonies like those started by the LandSettlement Association. Here, although there is ample land for convertingevery possible waste into humus, the water-borne method of sewagedisposal and the dust-carts of the crowded town have been slavishlycopied. In an interesting paper published in the British Medical Journalof February 9th, 1924, Dr. L. J. Picton, then Medical Officer of Healthof the Winsford Urban District, Cheshire, pointed out how easy it wouldbe to apply Dr. Poore's principles to a garden city.
'A plot of 4 acres should be taken on the outskirts of a town and twentyhouses built upon it. Suppose the plot roughly square, and the road toskirt one corner of it. Then this corner alone will possess that valuablequality "frontage". Sacrifice this scrap of frontage by making a shortgravelled drive through it, to end blindly in a "turn-round" in themiddle of the plot. The houses should all face south--that is to say, alltheir living rooms should face south. They must therefore be oblong, withtheir long axes east and west (Fig. I). The larder, the lobby, lavatory,staircase and landing will occupy the north side of each house. The earthcloset is best detached but approached under cover--a cross-ventilatedpassage or short veranda, or, if upstairs, a covered bridge giving accessto it. The houses should be set upon the plot in a diamond-shapedpattern, or in other words, a square with its corners to north, south,east and west. Thus one house will occupy the northernmost point of theplot, and from it, to the south-east and south-west, will run a row ofsome five or six houses a side, arranged in echelon Just as platoons inechelon do not block each other's line of fire so houses thus arrangedwill not block each other's sunlight. A dozen more houses echeloned in aV with its apex to the south will complete the diamond-shaped lay-out.The whole plot would be treated as one garden, and one whole-time headgardener, with the help he needed, would be responsible for itscultivation. The daily removal of the closet earth and its use asmanure--its immediate committal to the surface soil and its lightcovering therewith--would naturally be amongst his duties. A gardenerusing manure of great value, not a scavenger removing refuse; a "gardenrate" paid by each householder, an investment productive of freshvegetables to be had at his door, and in one way or another repaying himhis outlay, not to speak of the amenity added to his surroundings,instead of a "sanitary rate" paid to be rid of rubbish--such are thebases of this scheme.'
Fig. 1 A model layout for 20 cottages
What is needed are a few working examples of such a housing scheme and apublished account of the results. These, if successful, would at onceinfluence all future building schemes in country districts and wouldpoint the way to a considerable reduction in rents and rates. Thegarden-city and water-borne sewage are a contradiction in terms.Water-borne sewage has developed because of overcrowding and the absenceof cultivated land. Remove overcrowding and the case for this wastefulsystem disappears. In the garden city there is no need to get rid ofwastes by the expensive methods of the town. The soil will do it far moreefficiently and at far less cost. At the same time the fertility of thegarden city areas will be raised and large crops of fresh vegetables andfruit--one of the factors underlying health--will be automaticallyprovided.
Such a reform in housing schemes will not stop at the outer fringes ofour towns and cities. It will be certain to spread to the villages and tothe country-side, where a few examples of cottage gardens, renderedfertile by the wastes of the inhabitants, are still to be found here andthere. More are needed. More will arise the moment it is realized thatthe proper utilization of the wastes of the population depends oncomposting processes and the correct use of humus. All the trouble, allthe expense, and all the difficulties in dealing with human wastes arisefrom following the wrong principle--water--and setting in motion a vasttrain of putrefactive processes. The principle that must be followed isabundant aeration at the beginning: the conversion of wastes into humusby the processes Nature employs in every wood and every forest.
GREENWELL, SIR BERNARD. 'Soil Fertility: the Farm's Capital,' Journalof the Farmers Club, 1939, p. 1.
HOWARD, SIR ALBERT. 'Preservation of Domestic Wastes for Use on the Land',Journal of the Institution of SanitaryEngineers, xliii, 1939, p. 173.
-------'Experiments with Pulverized Refuse as a Humus-Forming Agent',Journal of the Institute of Public Cleansing,xxix, 1939, p. 504.
JONES, B. B., and OWEN, F. Some Notes on the Scientific Aspects ofControlled Tipping, City of Manchester, 1934.
PICTON, L. J. 'The Economic Disposal of Excreta: Garden Sanitation',British Medical Journal, February 9th, 1924.
POORE, G. V. Essays on Rural Hygiene, London, 1894.
Public Cleansing Costing Returns for the year ended March 31st, 1938,H. M. Stationery Office, 1939.
PART III HEALTH, INDISPOSITION, AND DISEASE IN AGRICULTURE
The transformation of soil fertility into a crop is only possible bymeans of oxidation processes. The various soil organisms--bacteria andfungi in particular--as well as the active roots need a constant supplyof oxygen. As soon as this was recognized, aeration became an importantfactor in the study of the soil. In this matter, however, practice haslong preceded theory: many devices such as sub-soil drainage,sub-soiling, as well as mixed cropping--all of which assist theventilation of the soil--have been in use for a long time.
The full significance of soil aeration in agriculture has only beenrecognized by investigators during the last quarter of a century. Thereason is interesting. Till recent years most of the agriculturalexperiment stations were situated in humid regions where the rainfall iswell distributed. Rain is a saturated solution of oxygen and is veryeffective in supplying this gas to the soil whenever percolation ispossible. Hence in such regions crops are not likely to suffer from pooraeration to anything like the same extent as those grown in the aridregions of North-West India where the soils are silt-like and most of themoisture has to be supplied by irrigation water low in dissolved oxygen.Such soils lose their porosity with the greatest ease when flooded; theminute particles run together and form an impermeable surface crust. Onlywhen the humus content is kept high can adequate permeability bemaintained. Long before the advent of the modern canal, the cultivatorsof India had acted on this principle. The organic matter content of theareas commanded by wells has always been maintained at a high level.Irrigation engineers and Agricultural Departments have been slow toutilize this experience. Canal water has been provided, but no steps havebeen taken simultaneously to increase the humus content of the soil.
It follows from the constant demands of the soil for fresh air that anyagency which interferes, even partially or temporarily, with aerationmust be of supreme importance in agriculture. A number of factors occurwhich bring about every gradation between a restricted oxygen supply andcomplete asphyxiation. The former result in infertility, the latter inthe death of the soil.
PLATE III. Rainfall, Tempeature, Humidity, and Drainage, Pusa, 1922
How does the plant respond to soil conditions in which oxygen becomes thelimiting factor? Generally speaking there is an immediate reaction on thepart of the root system. This is well seen in forest trees and in theundergrowth met with in woodlands. The roots adjust themselves to the newconditions; the trees establish themselves and at the same time improvethe aeration and also add to the fertility of the soil; incidentally allother competitors are vanquished. Soil aeration cannot therefore bestudied as if it were an isolated factor in soil science. It must beconsidered along with (1) the responses of the root system to deficientair, (2) the relation between root activity and soil conditionsthroughout the year, and (3) the competition between the roots of variousspecies. In this way the full significance of this factor in agricultureand in the maintenance of soil fertility becomes apparent. This is thetheme of the present chapter. An attempt will be made to explain soilaeration as it affects the plant in relation to the environment and toshow how the plant itself can be used as a research agent.
THE SOIL AERATION FACTOR IN RELATION TO GRASS AND TREES
Between the years 1914 and 1924 the factors involved in the competitionbetween grass and trees were investigated by me at Pusa. Three mainproblems were kept in view, namely, (1) why grass can be so injurious tofruit trees, (2) the nature of the weapons by which forest trees vanquishgrass, and (3) the reaction of the root system of trees to the aerationof the soil. An account of this study was published in the PROCEEDINGS OFTHE ROYAL SOCIETY OF LONDON in 1925 (B, vol. xcvii, pp. 284-321). As theresults support the view that in the investigation of the soil aerationfactor the plant can always make an important contribution, a summary ofthe main results and a number of the original illustrations have beenincluded in this chapter.
The climatic factors at Pusa are summed up in Plate III. It will be seenthat after the break of the south-west monsoon in June, the humidityrises followed by a steady upward movement in the ground water-level tillOctober when it falls again. In 1922 the total rise of the sub-soilwater-level was 16.5 feet, a factor which is bound to interfere with theoxygen supply, as the soil air which is rich in carbon dioxide is slowlyforced into the atmosphere by the ascending water-table.
The soil is a highly calcareous silt-like loam containing about 75 percent. of fine sand and about 2 per cent. of clay. About 98 per cent. willpass through a sieve of 80 meshes to the linear inch. There is no line ofdemarcation between soil and sub-soil: the subsoil resembles the soil andconsists of alternating layers of loam, clay, and fine sand down to thesub-soil water, which normally occurs about 20 feet from the surface. Thepercentage of calcium carbonate is often over 30, while the availablephosphate is in the neighbourhood of 0.001 per cent. In spite of this lowcontent of phosphate, the tract in which Pusa is situated is highlyfertile, maintaining a population of over 1,200 to the square mile andexporting large quantities of seeds, tobacco, cattle, and surplus labourwithout the aid of any phosphatic manures. The facts relating toagricultural production in this tract flatly contradict one of thetheories of agricultural science, namely, the need for phosphaticfertilizers in areas where soil analysis shows a marked deficiency inthis element. Two other factors, however, limit crop production--shortageof humus and loss of permeability during the late rains due to acolloidal condition of the soil; the pore spaces near the surface becomewater-logged; percolation stops and the soil is almost asphyxiated, acondition which is first indicated by the behaviour of the root systemand then by restricted growth.
FIG. 2. Plan of Experimental Fruit Area, Pusa.
For the investigation of the soil aeration factor in relation to grassand trees at Pusa, eight species of fruit trees--three deciduous and fiveevergreen--were planted out in three acres of uniform land, each speciesbeing raised from a single parent. The plan (Fig. 2) gives furtherdetails and makes the arrangement clear. Two years after planting, whenthe trees were fully established and remarkably even, a strip includingnine trees of each of the eight rows was laid down to grass. The two endplots, which were clean cultivated, served as controls. When the grasswas well established and its injurious effect on the young trees wasclearly marked, the three southern trees of the grass plot were providedwith aeration trenches, 18 inches wide and 24 inches deep filled withbroken bricks, these trenches being made midway between the lines oftrees. To ascertain the effect of grass on established trees in fullbearing, the southern strip of the northern control plot was grassed overin 1921. The general results of the experiment, as seen in 1923, areshown in Plate IV. The harmful effect of grass on fruit trees at Pusa iseven more intense than on clay soils like those of Woburn in GreatBritain. Several species were destroyed altogether within a few years.
PLATE IV. The harmful effects of grasss on fruit trees, Pusa, 1923
As great differences in root development were observed between the treesunder grass, under grass with aeration trenches, and under cleancultivation, the first step in investigating the cause of the harmfuleffect of grass appeared to be a systematic exploration of the rootsystem under clean cultivation so as to establish the general facts ofdistribution, to ascertain the regions of root activity during the yearand to correlate this information with the growth of the above groundportion of the trees. This was carried out in 1921 and the work wasrepeated in 1922 and again in 1923. The method adopted was direct: toexpose the root system quickly and to use a fine waterjet for freeing theactive roots from the soil particles. By using a fresh tree for eachexamination and by employing relays of labourers, it was possible toexpose any desired portion of the root system down to 20 feet in a fewhours and to make the observations before the roots could react to thenew conditons.
THE ROOT SYSTEM OF DECIDUOUS TREES
The root systems of three deciduous trees--the plum, the peach, and thecustard apple--were first studied. The results obtained in the threespecies were very similar, so it is only necessary to describe in detailone of them--the plum.
The local variety of plum sheds its leaves in November and flowersprofusely in February and March. The fruit ripens in early May, thehottest period of the year. The new shoots are produced during the hotweather and early rains.
The root system is extensive and appears at first to be entirelysuperficial and to consist of many large freely branching roots runningmore or less parallel to the surface in the upper 18 inches of soil.Further exploration disclosed a second root system. From the under sideof the large surface roots, smaller members are given off which growvertically downwards to about 16 feet from the surface. These break upinto many branches in the deep layers of moist fine sand, just above thewater-table. The Indian variety of plum therefore has two root systems(Plate V, Fig. I). The deep root system begins to develop soon after theyoung trees are planted out. In August 1923 the root systems of youngcustard apples, mangoes, guavas, limes, and loquats, planted in March1922 were examined. The young vertical roots varied in length from 10inches in the custard apple and lime to 1 foot in the mango, 1 foot 2.5inches in the guava and 1 foot 8 inches in the loquat. Newly plantedtrees form the superficial system first of all, followed rapidly by thedeep systems.
PLATE V. Plum (Prunus communis, Huds.)Fig. 1. Superficial and deep roots (April 25, 1921)Fig. 2. The repair of the deep root-system (August 6, 1923)Fig. 3. Superficial rootlets growing towards the surface (August 12, 1922)Figs. 4 and 5. New wood under cultivation and grass (January 25, 1923)Figs. 6 and 7. New shoots and leavesunder clean cultivation(April 5, 1923)Figs. 8 and 9. The corresponsing growth under glass (April 5, 1923)
During the resting period (December to January) occasional absorbingroots are formed in the superficial system. When flowering begins, theformation of new rootless spreads from the surface to the deep soillayers. As the surface soil dries in March, the active roots on thesuperficial system turn brown and die and this portion passes into adormant condition. From the middle of March to the break of the rains inJune, root absorption is confined entirely to the deeper layers of soil.Thus on April 14th, 1921, when the trees were ripening their fruit andmaking new growth during a period of intense heat and dryness, most ofthe water, nitrogen, and minerals necessary for growth were absorbed froma layer of moist fine sand between 10 feet 6 inches and 15 feet below thesurface. This state of affairs continues till the break of the rains inJune when a sudden change takes place. The moistening of the surface soilrapidly brings the superficial root system into intense activity. Thesehitherto dormant roots literally break into new active rootlets in alldirections, the process beginning about thirty hours after the first fallof rain. In the early monsoon therefore the trees use the whole of theroot system, both superficial and deep. A change takes place during lateJuly as the level of the ground water rises. In early August active rootsare practically confined to the upper 2 feet of soil. Absorption is nowrestricted to the surface system. At this period the active roots reactto the poor soil aeration due to the rise in the ground water-level bygrowing towards the atmosphere and even out of the soil into the air,particularly under the shade of the trees and where the soil is coveredby a layer of dead leaves (Plate V, Fig. 3). This aerotropism continuestill early October, when the growth above ground stops and the treesripen their wood preparatory to leaf fall and the cold weather rest.During October, as the level of the ground water falls and air is drawninto the soil, there is some renewal of root activity near the surfaceand down to 3 feet.
One interesting exception to this periodicity in the root activity of theplum occurs. Falls of rain, nearly an inch in amount, sometimes occurduring the hot season. The effect on the superficial root system of theplum of three of these storms was investigated. When the rainfall was0.75 of an inch or more, the surface roots at once responded and produceda multitude of new absorbing roots. As the soil dried these ceased tofunction and died. In one case, where the rainfall was only 0.23 inches,no effect was produced. Irrigation during the hot weather acts in asimilar manner to these sudden falls of rain. It maintains the surfaceroot system in action during this period and explains why irrigationduring the hot months is necessary on the alluvium if really good qualityfruit is to be obtained. It is true that without artificial watering thetrees ripen a crop at Pusa, but in size and quality the crop is greatlyinferior to that obtained with the help of irrigation. Either root systemwill produce a plum. High quality is obtained only when the surfacesystem functions; poor quality always results when the deep system onlyis in action.
In the detailed examination of the active surface roots of the plum andof the seven other species in this experiment, fresh fungous mycelium wasoften observed running from the soil towards the growing roots. In thedeeper soil layers this was never observed. In all probability thismycelium is connected with the mycorrhizal association so common in fruittrees. This matter was not carried further at the time. It is, however,more than probable that all the eight species of fruit trees in the PusaExperiment are mycorrhiza-formers and that the fungus observed round theactive roots was concerned with this association. The mycorrhizalrelationship in the surface roots is probably involved in the productionof high quality fruit. Plants with two root systems such as these aretherefore admirably adapted for the future study of the relation betweenhumus in the soil, the mycorrhizal association, and the development ofquality. It would not be difficult to compare plants grown side by sideon the sub-soil (to remove the humus occurring in the surface soil), theone manured with complete artificials, the other with freshly preparedhumus. In the former there would be little or no mycorrhizal invasion; inthe latter it would probably be considerable. If, as is most likely, themycorrhizal association enables the tree to absorb nutrients in theorganic form by the digestion of fungous mycelium, this would explain whyquality only results when the surface roots are in action.
Support for the view of plant nutrition suggested in the precedingparagraph was supplied by the custard apple, the root development ofwhich is similar to that of the plum and peach. In the custard apple newshoots are formed in the hot weather when the water, nitrogen, andnutrients are obtained from the deep soil layers only. After the break inthe rains and the resumption of root activity on the surface, the leavesincrease in size (from 5.8 x 2.6 cm. to 10.5 x 4.5 cm.), develop a deeperand healthier green, while the internodes lengthen. The custard applerecords the results of these various factors in the size and colour ofits leaves and in this way acts as its own soil analyst.
While this book was being printed specimens of the young active roots ofthe custard apple, mango, and lime were collected in Mr. Hiralal'sorchard, Tukoganj, Indore, Central India, on November 11th, 1939, by Mr.Y. D. Wad. They were examined by Dr. Ida Levisohn on December 19th, 1939,who reported that all three species showed typical endotrophicmycorrhizal infection indicated macroscopic ally by the absence of roothairs, or great reduction in their number, and, in the mangoparticularly, by beading. The active hyphae in all three cases were oflarge diameter, with thin walls and granular contents, the digestionstages occurring in the inner cortex with clumping of mycelium, remainsof hyphae and homogeneous granular masses. Absorption of the fungusappeared to be taking place with great rapidity. In the custard apple thesame kind of mycelium was found outside the roots and connected withthem.
THE ROOT SYSTEM OF EVERGREENS
The most interesting root system of the five evergreens studied--mango,guava, litchi, sour lime, and loquat--was the guava.
PLATE VI. Guava (Psidium Guyava, L)Fig. 1. Superficial and deep roots (November 23, 1921)Fig. 2. The influence of soil texture on the formation of the rootlets(March 29, 1921)Fig. 3. The root-system under grass (April 21, 1921)Fig. 4. Superficial rootlets growing to the surface (August 28, 1921)Fig. 5. Formation of new rootletsin fine sand following the fall ofthe ground water (November 20, 1921)Fig. 6. Reduction in the size of leaves after 20 months under grass(right).
The guava drops its foliage in early March, simultaneously producing newleaves. It proved an excellent plant for the study of the root system, asthe reddish roots are strongly developed and easy to follow in a greyalluvial soil like that of Pusa. There is an abundant superficial systemgiving off numerous branches which grow downwards to the level ofpermanent water (Plate VI, Fig. 1). The whole of the root system,superficial and deep, was found to be active at the beginning of the hotweather (March 21st, 1921), the chief zone of activity occurring in amoist layer of fine sand 10 feet 4 inches to 14 feet 7 inches from thesurface. As the hot weather became established, the absorbing roots ofthe guava near the surface dried up and root activity was confined to thedeeper layers of soil. In 1922 the monsoon started on June 3rd. Anexposure of the surface roots was made on June 5th, forty-eight hoursafter the rains started. From 1 foot 5 inches to 12 feet new roots werefound in large numbers, the longest measuring I cm. As the soil becamemoistened by the early rains, the dormant zone produced new roots fromabove downwards till the whole root system became active. After July achange takes place as the ground water rises, the deep roots becomingdormant as immersion proceeds. On August 25th, 1922, root activity wasmainly confined to the surface system in the upper 29 inches of soil, thelast active root occurring at 40 inches. In the late rains the activeroots escape asphyxiation by becoming strongly aerotropic (Plate VI, Fig.4). An interesting change takes place after the level of the sub-soilwater falls in October and the aeration of the lower soil layers isrenewed. The deep root system again becomes active in November, thedegree of activity depending on the monsoon rainfall (Plate VI, Fig. 5).In 1921, a year of short rainfall when the rise of the ground water wasvery small, the deep roots came into activity in November down to 15 feet3 inches. The next year--November 1922--when the monsoon and the rise ofthe ground water were both normal, root activity did not extend below 5feet 7 inches.
Although the guava is able to make new growth during the hot season bymeans of its deep root system it is a decided advantage if the surfaceroots are maintained in action by means of irrigation. Surface wateringin the hot weather of 1921 increased the size of the leaves from 9.1 x4.0 cm. to 11.6 x 5.0 cm. and greatly improved their colour.
The root system and the development of active roots in the mango, litchi,lime, and loquat follow generally what has been described in the guava.All these species give off vertical roots from the surface system, but inthe case of the litchi and the lime these did not penetrate to the deeperlayers. The roots of all four species exhibit marked aerotropism in thelate rains. The vertical roots of the lime were always unable topenetrate the deeper layers of clay.
THE HARMFUL EFFECT OF GRASS
The harmful effect of grass on fruit trees varies with the species andwith the period in the life of the tree when the grass is planted. Youngtrees are more adversely affected than fully developed individuals, whichcontain large quantities of reserves in the wood. Deciduous speciessuffer more than evergreens. These facts suggest that the harmful effectof grass is a consequence of starvation.
The effect of grass on young trees was first studied. The custard applewas the most sensitive. The trees were killed in 1916 within the firsttwo years after the grass was planted. Next in order of susceptibilitywere the loquat (all died before the end of 1919), the plum, the lime,and the peach. The litchi and the mango just managed to maintainthemselves. The guava was by far the least affected, the trees undergrass being almost half the height of those under clean cultivation.
Grass not only reduces the amount of new growth but affects the leaves,branches, old wood, and fruit as well as the root system. The resultsrelating to the above ground portion of the trees closely follow thosedescribed by the Woburn investigators. Compared with the foliage producedunder clean cultivation, the leaves from the trees under grass appearlater, are smaller and yellower and fall prematurely. The internodes areshort. The bark of the twigs is light coloured, dull, and unhealthy andquite different from that of healthy trees. The bark of the old wood hasa similar appearance and attracts lichens and algae to a much greaterextent than that of the cultivated trees. The trees under grass flowerlate and sparingly. The fruit is small, tough, very highly coloured, andripens earlier than the normal.
The effect of grass on the root system is equally striking. Except in theguava, the effect of grass on the superficial system is to restrict theamount of root development, to force the roots below the grass, and toreduce the number of active roots during the monsoon. The guava is anexception. The surface system is well developed, the roots are not drivendownwards by the grass while active rootless are readily formed in theupper 4 inches of soil soon after the rains begin, very much as in thecultivated trees. In August 1922, when the ground water had risen to itshighest point, the absorbing roots of the guava were found in the surfacefilm of soil, and also above the surface among the stems of the grass.The grass carpet therefore acts as an asphyxiating agency in all thesespecies, the guava excepted.
The grass covering has no appreciable effect either on the development oron the activity of the deep roots. This portion of the root system wasexplored during the hot weather of 1921 in the case of the guava (PlateVI, Fig. 3), mango, and litchi and results were obtained very similar tothose in the corresponding cultivated trees.
Grass not only affects the roots underneath but also the development ofthose of the neighbouring trees under cultivation. Such roots either turnaway from the grass, as in the custard apple, or else turn sharplydownwards before they reach it.
A number of conclusions can be drawn from these root exposures. Thecustard apple, loquat, peach, and lime are unable to maintain theirsurface root systems under grass, but behave normally as regards the deeproot system. Only the guava is able to get its roots above those of thegrass during the rains.
The study of the harmful effect of grass on established trees alsoyielded interesting results. In this case the trees carried amplereserves in the wood and, as might be expected, the damage was lessspectacular than in the case of young trees with little or no reserves.The order of susceptibility to grass, however, was very much the same inthe two cases. When the fully-grown trees were first put under grass inAugust 1921, the grass at first grew poorly in tufts with bare groundbetween. Even this imperfect covering soon affected the custard apples,loquats, peaches, and litchis. By the rains of 1922 the grass becamecontinuous; the effect on the trees was then much more marked.
In the plum interesting changes occurred. In July 1922, less than a yearafter planting the grass, the new shoots showed arrested growth and thefoliage was attacked by leaf-destroying insects, which, however, ignoredthe leaves of the neighbouring cultivated plot. If the insects were thereal cause of the trouble, it is difficult to see why the infection didnot spread beyond the trees under grass. In January 1923 the averagelength of the new wood in these trees was 1 foot 5 inches compared with 3feet 7 inches in the controls. The twigs were dull and purplish, theinternodes were short (Plate V, Fig. 5). In February 1923 flowering wasrestricted and in April only tufts of leaves were formed at the ends ofthe branches instead of new shoots (Plate V, Fig. 8). Early in 1924, whenI left Pusa and had to discontinue the work, a great deal of die-back wastaking place.
Very similar results were obtained in all the species except the mango,which resisted grass better than any of the others. No definite effectwas observed in this species till June 1923, when the foliage becamedistinctly lighter than that of the cultivated trees. The general resultsbrought about by grass in all these cases suggested that the trees wereslowly dying from starvation.
A year after the grass was planted and the grass effect was becomingmarked, the root system of these established trees was examined. InAugust 1922 the plums, peaches, custard apples, mangoes, litchis, andloquats under grass were found to have produced very few active rootlessin the upper foot of soil compared with the controls. In the case of thecustard apples and the loquats, which suffered most from grass, there wasa marked tendency for the new roots to grow downwards and away from thegrass. No differences were observed in the dormancy or activity of thedeep root system as compared with the controls. The deep roots behavedexactly like those under clean cultivation.
FIG. 4. The effect of burrowing rats on the growth of the plum undergrass (June 21st, 1923)
During these examinations two instances of the striking effect ofincreased aeration on root development were observed. In July 1923burrowing rats took up their quarters under one of the limes and one ofthe loquats, in each case on the southern side. Shortly afterwards theleaves just above the rat holes became very much darker in colour thanthe rest. Examination of the soil immediately round the burrows showed acopious development of new active rootless, far greater even than in thesurface soil of the cultivated plot. The extra aeration had a wonderfullystimulating effect on the development of active roots, even under grass.The appearance of the leaves suggested an application of nitrogenousmanure. Similar observations were made in the case of the plum (Fig. 4).Here the burrows caused a dying tree to produce new growth.
THE EFFECT OF AERATION TRENCHES ON YOUNG TREES UNDER GRASS
The effect of aeration trenches in modifying the influence of grasssuggests that one of the factors at work is soil asphyxiation. In thecase of the custard apple and the lime the aeration trenches had noeffect; all the trees died. The death of the plums was delayed by theaeration trenches. The loquats, litchis, and mangoes benefitedconsiderably. In the guavas the trees provided with aeration trencheswere indistinguishable from those under grass. The general results areshown in Table 8, in which the measurements of a hundred fully-developedleaves, made in March 1921, are recorded.
The reduction in leaf size under grass
Grass Grass with aeration Cultivated (cm.) trenches (cm.) (cm.)Plum 3.2 x 1.1 4.6 x 1.7 7.1 x 2.9Peach 7.1 x 1.8 8.2 x 2.3 11.4 x 3.1Guava 8.1.x 3.2 10.6 x 4.4 11.3 x 4.4Mango 11.2 x 2.9 13.7 x 3.8 20.9 x 5.5Litchi 8.9 x 2.4 11.5 x 3.4 12.2 x 3.5Lime 3.8 x 1.6 5.2 x 2.1 6.4 x 3.4Loquat Trees dead 16.4 x 4.6 22.1 x 5.9
At the end of 1920 the roots were exposed to a depth of 2 feet in orderto ascertain the effect of the extra aeration on the development of thesuperficial system. The results were interesting. In all cases thesuperficial roots were much larger and better developed than those undergrass, except in the guava where no differences in size could be detected.The roots were attracted by the trenches, often branching considerablyin the soil at the side of the trenches themselves. The aerationtrenches are made use of only during the monsoon phase. After thebreak of the rains, new active roots are always found in or near thetrenches first, after which a certain amount of development takes placeunder the grass.
The deep root system of the trees provided with aeration trenches behavedexactly like the controls.
THE RESULTS OBTAINED
The general results obtained with clean cultivation, grass, and grasswith aeration trenches are shown in Plate IV, in which representativetrees from the various plots have been drawn to scale. The drawingsgive a good idea of the main results of the experiment, namely:(1) the extremely deleterious effect of grass on young trees;(2) the less harmful effect of the same treatment on mature trees;(3) the partial recovery which sometimes takes place from the aerationtrenches; and (4) the exceptional nature of the results with the guava,where the trees are able to grow under grass, but with reduced vigour,and where the aeration trenches have had little or no effect.
As would be expected from these results even a temporary removal of thegrass cover has a profound effect. Whenever the roots of a tree undergrass are exposed (for which purpose the grass has to be removed fora few days) there is an immediate increase in growth, accompanied bythe formation of larger and darker-coloured leaves. The effect isclearly visible in the foliage above the excavation for as long astwo years, but the rest of the tree is not affected.
THE CAUSE OF THE HARMFUL EFFECT OF GRASS
The examination of the root system of these eight species suggested thatthe first step in working out the cause of the harmful effect of grasswould be to make a periodical examination of the soil gases.Determinations of the amount of CO2 in the soil-air at a depth of 9 to 12inches were carried out during 1919 under grass, under grass withaeration trenches, and under cultivated soil. About 10 litres of airwere drawn out of the soil at each determination and passed throughstandard baryta which was afterwards titrated in the ordinary way.The 1919 results are given in Table 9 and are set out graphicallyin Fig. 5.
Percentage by volume of carbon dioxide in the soil-gasunder grass and clean cultivation, Pusa, 1919
Date and month when Plot no. 1 Plot no 2 Plot no 2 Rainfallsoil-gas was aspirated grassed grassed, but surface in inchesand analysed partially aerated cultivated since by trenches 1/1/1919
January 13, 14 and 17 0.444 0.312 0.269 NilFebruary 20 and 21 0.472 0.320 0.253 1.30March 21 and 22 0.427 0.223 0.197 1.33April 23 and 24 0.454 0.262 0.203 2.69May 16 and 17 0.271 0.257 0.133 3.26June 17 and 18 0.341 0.274 0.249 4.53July 17 and 18 1.540 1.090 0.304 14.61August 25 and 26 1.590 0.836 0.401 23.29September 19 and 20 1.908 0.931 0.450 30.67October 21 and 22 1.297 0.602 0.365 32.90November 14 and 15 0.853 0.456 0.261 32.90December 22 and 23 0.398 0.327 0.219 32.92
The results of 1920 and 1921 confirm these figures in all respects.Table 9 shows that during the monsoon the volume of carbon dioxide inthe pore spaces under grass is increased about fivefold in comparisonwith the soil-air of cultivated land. As this gas is far more solublein water than oxygen, the amounts of carbon dioxide actually dissolvedin the water-films in which the root-hairs work would be much higherthan the figures in the table suggest.
The production of large amounts of carbon dioxide in the soil-air duringthe rains would also affect the formation of humus, nitrification, andthe mycorrhizal relationship, all of which depend on adequate aeration.Considerable progress was made in the investigation of the supply ofcombined nitrogen. At all periods of the year, except at the break ofthe rains, the amount of nitric nitrogen in the upper 18 inches of soilunder grass varied from 10 to 20 per cent. of that met with in thecultivated plots. When the shortage of nitrogen in the case of theguava was made up by means of sulphate of ammonia during the rainsof 1923, the trees under grass at once responded and produced fruitand foliage hardly distinguishable in size from the controls.
FIG. 5. Carbon dioxide in soil atmosphere, Pusa, 1919.
In the case of the litchi and loquat, the roots of which are unableto aerate themselves in the rains by forcing their way through the grassto the surface, heavy applications of combined nitrogen improved thegrowth, but a distinctly harmful effect remained--the manured treesas regards size and colour of the leaves, time of flowering, andproduction of new shoots occupying an intermediate position betweenthe unmanured trees under grass and those under clean cultivation.These results are very similar to those obtained with apples at Cornell.At both places grass led to the disappearance of nitrates in the soiland restricted root development. The effect was only partially removedby the addition of nitrate of soda.; In the guava, however, combinednitrogen removes the harmful effect because the roots of this tree areable to obtain all the oxygen they need. The guava, therefore, suffersfrom only one of the factors resulting from a grass carpet--lack ofnitrate. The litchi and the loquat suffer from another factor aswell--lack of oxygen.
FOREST TREES AND GRASS
Although the grass carpet acts as an asphyxiating agent to the rootsof all the fruit-trees investigated except the guava, the ordinaryIndian forest trees thrive under grass. Between the years 1921 and 1923the relation between the grass carpet and the roots of the followingfifteen forest trees was investigated (Table 10). All thrive remarkablywell under grass and show none of the harmful effects exhibited byfruit-trees.
Most of the forest trees in the plains of India flower and come intonew leaf in the hot season and then proceed to form new shoots. Afterthe early rains a distinct change is visible in the size, colour, andappearance of the foliage. The leaves become darker and more glossy;the story told by the young shoots of the custard apple is repeated.
Forest trees under grass in the Botanical Area, Pusa
Species Time of flowering Time of leaf-fallPolyalthia longifoliaBenth. & Hook, f. February-April AprilMelia Azadirachta L. March-May MarchFicus bengalensis L. April-May MarchFicus religosa L. April-May DecemberFicus infectoria Roxb. February-May December-JanuaryMillingtonia hortensisLinn., f. November-December MarchButea frondosa Roxb. March FebruaryPhyllanthus Emblica L. March-May FebruaryTamarindus indica L. April-June March-AprilTectonia grandis Linn., f. July-August February-MarchThespesia populnea Corr. Throughout the year but chiefly in the cold season AprilPterospermum acerifoliumWilld. March-June January-FeburaryWrightia tomentosa Roem.& Schult. April-May January-FebruaryLagerstroemia Flos-ReginaRetz May December-JanuaryDalbergia Sissoo Roxb. March December-January
Examination of the superficial root systems of the fifteen speciesduring the rains of 1922 and 1923 yielded remarkably uniform results.All the trees produced abundant, normally developed active rootless inthe upper 2 or 3 inches of soil and also on the surface; they thereforecompete successfully with grass both for oxygen and nitrates. The largesuperficial roots were also well developed and compared favourably withthe corresponding root system of fruit-trees under clean cultivation.The grass carpet had apparently no harmful effect on the root systemnear the surface.
Between the hot weather of 1921 and the early months of 1924 thecomplete root systems of these fifteen species were investigated. In allcases the large surface roots gave off thin branches which grewvertically downwards to the cold-season level of the ground water. Rootactivity in all cases was practically confined in the hot season to thedeep moist layers of sand between 10 and 20 feet below the surface, theroots always making the fullest use of the tunnels of Termites and otherburrowing insects for passing easily through clay layers from one zoneof sandy soil to the next below. Cavities in the soil were always fullyused for root development. Soon after the rains the dormant surfaceroots burst into activity. As the ground water rose the deep root systembecame dormant; in August the active surface roots always showed markedaerotropism. The formation of nitrates which takes place about the timethe cold-season crops are sown was followed by a definite burst ofrenewed root activity in the surface soil, followed by the production ofnew shoots and leaves. As the ground water falls in the autumn and thesoil draws in oxygen, the formation of active roots follows thedescending water-table exactly as has been described in the case of theguava.
The facts of root distribution and periodicity in root activity inforest trees explain why these trees do so well under grass and are ableto vanquish it if allowed free competition. The chief weapons whichenable forest trees to oust grasses and herbs from the habitat are thefollowing:
1. The deep root system admits of growth during the dry season when thegrass is dormant, thereby enabling the trees to utilize moisture andfood materials in the soil down to at least 20 feet. This markedlyextends the period of assimilation.
2. The habit of trees is a great advantage in the struggle for light.
3. The active roots of the surface system are resistant to poor soilaeration, and are able to reach the surface and compete successfullywith the grass for oxygen and for minerals.
The character which distinguishes forest trees from fruit-trees is thepower possessed by the surface roots of the former to avoid theconsequences of poor soil aeration by forcing their way through a grasscarpet in active growth to the air and to obtain oxygen as well as ashare of the nitrates in the surface soil. The surface roots of mostfruit-trees are very susceptible to carbon dioxide and try to avoid itby growing downwards. The trees are therefore deprived of oxygen and ofcombined nitrogen during the rains, and slowly starve. The guava is anexception among fruit-trees. Here the active roots reach the surface inthe rains and the trees are able to maintain themselves. This explainswhy the pastures of Grenada and St. Vincent in the West Indies are sorapidly invaded and destroyed by the wild guava. The hedgerows andpastures of Great Britain if left to themselves behave in a similar way.The hedgerows soon begin to invade the fields. Young trees make theirappearance; grass areas become woodland. The transformation, however, ismuch slower in Great Britain than in the tropics.
These studies on the root development of tropical forest trees throw agood deal of light on the soil aeration factor and the part the plantcan play in such investigations. The movement of the ground wateraffects soil aeration directly. The two periods--the beginning and endof the rainy season--when the surface soil contains abundant air andample moisture and when the temperature is favourable for nitrification,correspond exactly with times when nitrates accumulate and when growthis at its maximum. When soil aeration is interfered with during therains by two factors, (1) the rise of the ground water, and (2) theformation of colloids in the surface soil, the plant roots respond bygrowing to the surface. Root development, therefore, is an importantinstrument in such an investigation when examined throughout the year.
The root development of trees influences the maintenance of soilfertility in the plains of India and indeed in many other regions. Thedead roots provide the deeper layers of soil with organic matter and analmost perfect drainage and aerating system. The living roots comb theupper 20 feet of soil for such minerals as phosphates and potash whichare used in the green leaves. These leaves in due course are convertedinto humus and help to enrich the surface soil. This explains why thesoils of North Bihar, although very low in total and availablephosphates, are so exceedingly fertile and yield heavy crops without anyaddition of mineral manures. The figures given by the analysis of thesurface soil must be repeated in the lower layers and should beinterpreted not in terms of the upper 9 inches but of the upper 20 feet.
The tree is the most efficient agent available for making use of theminerals in the soil. It can grow almost anywhere, it will vanquish mostof the other forms of vegetation, and it will leave the soil in a highlyfertile condition. It follows therefore that the trees and shrubs of thehedgerows, parks, and woodlands of countries like Great Britain mustcontinue to be used for the maintenance of soil fertility. In Saxontimes most of our best land was under forest. The fertility stored inthe soil made the gradual clearing of this woodland worth while. In thefuture, when agriculture comes into its own and when it is no longerregarded solely as an industry, it may be desirable to embark on longterm rotations in which woods and park-land are turned into arable, andworn-out arable back into woodland or into mixed grass and trees. Inthis way the root system of the tree can be used to restore soilfertility.
THE AERATION OF THE SUB-SOIL
One of the universal methods of improving aeration is subsoiling. Themethods adopted vary greatly according to the factor which hasinterfered with aeration and the means available for improving theair-supply.
In temperate regions the chief factor which cuts off the sub-soil fromthe atmosphere is shortage of humus aggravated by impermeable pans(produced by the plough and by the soil particles themselves) or apermanent grass carpet accompanied by the constant treading of animals.The result in all cases is the same--the supply of air to the sub-soilis reduced.
In loamy soils plough-pans develop very rapidly if the content oforganic matter falls off and the earthworm population declines. Awell-defined zone of close and sticky soil is formed just under theplough sole which holds up water, thereby partly asphyxiating thesub-soil below and water-logging the soil above.
In sandy soils as well as in silts, pans are formed with the greatestease from the running together of the particles, particularly whenartificials take the place of farm-yard manure and the temporary ley isnot properly utilized. One of the most interesting cases of panformation that I have observed in Great Britain was on the permanentmanurial plots of the Woburn Experiment Station, where an attempt togrow cereals year after year on the greensand by means of artificialmanures has been followed by complete failure of the crop. The soil hasgone on permanent strike. The destruction of the earthworm population bythe regular application of chemicals had deprived the land of itsnatural aerating agencies. Failure to renew the organic matter by asuitable rotation had resulted in a soil devoid of even a trace oftilth. About 9 inches below the surface, a definite pan (made up of sandparticles loosely cemented together) occurred, which had so altered theaeration of the sub-soil that the whole of these experimental plots werecovered with a dense growth of mares' tail (Equisetum arvense L.), aperennial weed which always indicates a badly aerated sub-soil. Natureas usual had summed up the position in her own inimitable fashion. Therewas no need of tabulated yields, analyses, curves, and statistics toexplain the consequences of improper methods of agriculture.
The conventional method of dealing with arable pans in this country isby means of some sub-soiling implement which breaks them up and restoresaeration. This should be accompanied whenever possible by heavydressings of farm-yard manure, so that the tilth can be improved and theearthworm population restored. Some deep-rooted crop like lucerne, oreven a temporary fey, should be called in to complete the cure.Sub-soiling heavy land under grass is proving even more advantageousthan on arable areas. This leads, as we have seen, to humus formationunder the turf and to an increase in the stock-carrying capacity of theland.
In the East the ventilation of the sub-soil is perhaps even moreimportant than in the West. In India, for example, one of the commonconsequences of the monsoon rainfall and of flooding the surface withirrigation water is pan formation on a colossal scale due to theformation of soil colloids--the whole of the surface soil tends tobecome a pan. This has to be broken up. The cultivators of the Orientset about this task in a very interesting way. Whenever they can use theroots of a leguminous crop as a sub-soiler they invariably employ thismachine. It has the merit of costing nothing, of yielding essential foodand fodder, and of suiting the small field. In the Indo-Gangetic plainthe universal sub-soiler is the pigeon pea, the roots of which not onlybreak up soil pans with ease but also add organic matter at the sametime. On the Western frontier the sub-soiling of the dense loess soilsis always done by the roots of a lucerne crop. On the black cotton soilsof Peninsular India where the monsoon rainfall converts the whole of thesurface soil into a vast colloidal pan, the agricultural situation issaved by the succeeding hot season which dries out this pan and reducesits volume to such an extent that a multitude of deep fissures occurright down to the sub-soil. The black soils of India plough and sub-soilthemselves. The moist winds, which precede the south-west monsoon in Mayand early June, replace some of the lost moisture; the heavy clods breakdown and when the early rains arrive a magnificent tilth can be preparedfor the cotton crop. The sub-soiling in this case is done by Nature; thecultivators merely give a subsequent cultivation and then sow the crop.
CLEMENTS, F. E. Aeration and Air Content: the Role of Oxygen in RootActivity, Publication No. 315, Carnegie Institution of Washington, 1921.
HOWARD, A. Crop Production in India: A Critical Servey of its Problems,Oxford University Press, 1924.
-------'The Effect of Grass on Trees', Proc. Royal Soc., Series B, xcvii,1925, p. 284.
LYON, T. L., HEINICKE, A. J., and WILSON, D. D. The Relation of SoilMoisture and Nitrates to the Effects of Sod on Apple Trees, Memoir 63,Cornell Agricultural Expt. Station, 1923.
THE DUKE OF BEDFORD, and PICKERING, S. U. Science and Fruit-Growing,London, 1919.
WEAVER, J. E., JEAN, F. C, and CRIST, J. W. Development andActivities of Crop Plants, Publication No. 316, Carnegie Institutionof Washington, 1922.
SOME DISEASES OF THE SOIL
Perhaps the most widespread and the most important disease of the soilat the present time is soil erosion, a phase of infertility to whichgreat attention is now being paid.
Soil erosion in the very mild form of denudation has been in operationsince the beginning of time. It is one of the normal operations ofNature going on everywhere. The minute soil particles which result fromthe decay of rocks find their way sooner or later to the ocean, but manymay linger on the way, often for centuries, in the form of one of theconstituents of fertile fields. This phenomenon can be observed in anyriver valley. The fringes of the catchment area are frequentlyuncultivated hills through the thin soils of which the underlying rocksprotrude. These are constantly weathered and in the process yield acontinuous supply of minute fragments in all stages of decomposition.
The slow rotting of exposed rock surfaces is only one of the forms ofdecay. The covering of soil is no protection to the underlying stratabut rather the reverse, because the soil water, containing carbondioxide in solution is constantly disintegrating the parent rock, firstproducing sub-soil and then actual soil. At the same time the remains ofplants and animals are converted into humus. The fine soil particles ofmineral origin, often mixed with fragments of humus, are then graduallyremoved by rain, wind, snow, or ice to lower regions. Ultimately therich valley lands are reached where the accumulations may be many feetin thickness. One of the main duties of the streams and rivers, whichdrain the valley, is to transport these soil particles into the seawhere fresh land can be laid down. The process looked at as a whole isnothing more than Nature's method of the rotation, not of the crop, butof the soil itself. When the time comes for the new land to be enclosedand brought into cultivation agriculture is born again. Such operationsare well seen in England in Holbeach marsh and similar areas round theWash. From the time of the Romans to the present day, new areas offertile soil, which now fetch 100 pounds an acre or even more, have beenre-created from the uplands by the Welland, the Nen, and the Ouse. Allthis fertile land, perhaps the most valuable in England, is the resultof two of the most widespread processes in Nature--weathering anddenudation.
It is when the tempo of denudation is vastly accelerated by humanagencies that a perfectly harmless natural process becomes transformedinto a definite disease of the soil. The condition known as soilerosion--a man-made disease--is then established. It is, however, alwayspreceded by infertility: the inefficient, overworked, dying soil is atonce removed by the operations of Nature and hustled towards the ocean,so that new land can be created and the rugged individualists--thebandits of agriculture--whose cursed thirst for profit is at the root ofthe mischief can be given a second chance. Nature is anxious to make anew and better start and naturally has no patience with the inefficient.Perhaps when the time comes for a new essay in farming, mankind willhave learnt a great lesson--how to subordinate the profit motive to thesacred duty of handing over unimpaired to the next generation theheritage of a fertile soil. Soil erosion is nothing less than theoutward and visible sign of the complete failure of a policy. The causesof this failure are to be found in ourselves.
The damage already done by soil erosion all over the world looked at inthe mass is very great and is rapidly increasing. The regionalcontributions to this destruction, however, vary widely. In some areaslike north-western Europe, where most of the agricultural land is undera permanent or temporary cover crop (in the shape of grass or leys), andthere is still a large area of woodland and forest, soil erosion is aminor factor in agriculture. In other regions like parts of NorthAmerica, Africa, Australia, and the countries bordering theMediterranean, where extensive deforestation has been practiced andwhere almost uninterrupted cultivation has been the rule, large tractsof land once fertile have been almost completely destroyed.
The United States of America is perhaps the only country where anythingin the nature of an accurate estimate of the damage done by erosion hasbeen made. Theodore Roosevelt first warned the country as to itsnational importance. Then came the Great War with its high prices, whichencouraged the wasteful exploitation of soil fertility on anunprecedented scale. A period of financial depression, a series ofdroughts and dust-storms, emphasized the urgency of the salvage ofagriculture. During Franklin Roosevelt's Presidency, soil conservationhas become a political and social problem of the first importance. In1937 the condition and needs of the agricultural land of the U.S.A. wereappraised. No less than 253,000,000 acres, or 61 per cent. of the totalarea under crops, had either been completely or partly destroyed or hadlost most of its fertility. Only 161,000,000 acres, or 39 per cent. ofthe cultivated area, could be safely farmed by present methods. In lessthan a century the United States has therefore lost nearly three-fifthsof its agricultural capital. If the whole of the potential resources ofthe country could be utilized and the best possible practices introducedeverywhere, about 447,466,000 acres could be brought into use--an areasomewhat greater than the present crop land area of 415,334,931 acres.The position therefore is not hopeless. It will, however, be verydifficult, very expensive, and very time-consuming to restore the vastareas of eroded land even if money is no object and large amounts ofmanure are used and green-manure crops are ploughed under.
The root of this soil erosion trouble in the United States is misuse ofthe land. The causes of this misuse include lack of individual knowledgeof soil fertility on the part of the pioneers and their descendants; thetraditional attitude which regarded the land as a source of profit;defects in farming systems, in tenancy, and finance--most mortgagescontain no provisions for the maintenance of fertility; instability ofagricultural production (as carried out by millions of individuals),prices and income in contrast to industrial production carried on by afew large corporations. The need for maintaining a correct relationbetween industrial and agricultural production so that both can developin full swing on the basis of abundance has only recently beenunderstood. The country was so vast, its agricultural resources were soimmense, that the profit seekers could operate undisturbed until soilfertility--the country's capital--began to vanish at an alarming rate.The present position, although disquieting, is not impossible. Theresources of the Government are being called up to put the land inorder. The magnitude of the effort, the mobilization of all availableknowledge, the practical steps that are being taken to save what is leftof the soil of the country and to help Nature to repair the damagealready done are graphically set out in Soils and Men, the Year Book ofthe United States Department of Agriculture of 1938. This is perhaps thebest local account of soil erosion which has yet appeared.
The rapid agricultural development of Africa was soon followed by soilerosion. In South Africa, a pastoral country, some of the best grazingareas are already semi-desert. The Orange Free State in 1879 was coveredwith rich grass, interspersed with reedy pools, where now only uselessgullies are found. Towards the end of the nineteenth century it began tobe realized all over South Africa that serious over-stocking was takingplace. In 1918 the Drought Investigation Commission reported that soilerosion was extending rapidly over many parts of the Union, and that theeroded material was silting up reservoirs and rivers and causing amarked decrease in the underground water-supplies. The cause of erosionwas considered to be the reduction of vegetal cover brought about byincorrect veld management--the concentration of stock in kraals,over-stocking, and indiscriminate burning to obtain fresh autumn orwinter grazing. In Basutoland, a normally well-watered country, soilerosion is now the most immediately pressing administrative problem. Thepressure of population has brought large areas under the plough and hasintensified over-stocking on the remaining pasture. In Kenya the soilerosion problem has become serious during the last three years, both inthe native reserves and in the European areas. In the former, wealthdepends on the possession of large flocks and herds; barter is carriedon in terms of live stock; the bride price is almost universally paid inanimals; numbers rather than quality are the rule. The naturalconsequence is over-stocking, over-grazing, and the destruction of thenatural covering of the soil. Soil erosion is the inevitable result. Inthe European areas erosion is caused by long and continuous overcroppingwithout the adoption of measures to prevent the loss of soil and tomaintain the humus content. Locusts have of late been responsible forgreatly accelerated erosion; examples are to be seen where the combinedeffect of locusts and goats has resulted in the loss of a foot ofsurface soil in a single rainy season.
The countries bordering the Mediterranean provide striking examples ofsoil erosion, accompanied by the formation of deserts which areconsidered to be due to one main cause--the slow and continuousdeforestation of the last 3,000 years. Originally well wooded, noforests are to be found in the Mediterranean region proper. Most of theoriginal soil has been washed away by the sudden winter torrents. InNorth Africa the fertile cornfields, which existed in Roman times, arenow desert. Ferrari in his book on woods and pastures refers to thechanges in the soil and climate of Persia after its numerous andmajestic parks were destroyed; the soil was transformed into sand; theclimate became arid and suffocating; springs first decreased and thendisappeared. Similar changes took place in Egypt when the forests weredevastated; a decrease in rainfall and in soil fertility was accompaniedby loss of uniformity in the climate. Palestine was once covered withvaluable forests and fertile pastures and possessed a cool and moderateclimate; to-day its mountains are denuded, its rivers are almost dry,and crop production is reduced to a minimum.
The above examples indicate the wide extent of soil erosion, the veryserious damage that is being done, and the fundamental cause of thetrouble--misuse of the land. In dealing with the remedies which havebeen suggested and which are now being tried out, it is essential toenvisage the real nature of the problem. It is nothing less than therepair of Nature's drainage system--the river--and of Nature's method ofproviding the country-side with a regular water-supply. The catchmentarea of the river is the natural unit in erosion control. In devisingthis control we must restore the efficiency of the catchment area as adrain and also as a natural storage of water. Once this is accomplishedwe shall hear very little about soil erosion.
Japan provides perhaps the best example of the control of soil erosionin a country with torrential rains, highly erodible soils, and atopography which renders the retention of the soil on steep slopes verydifficult. Here erosion has been effectively held in check, by methodsadopted regardless of cost, for the reason that the alternative to theirexecution would be national disaster. The great danger from soil erosionin Japan is the deposition of soil debris from the steep mountain slopeson the rice-fields below. The texture of the rice soils must bemaintained so that the fields will hold water and allow of the minimumof through drainage. If such areas became covered with a deep layer ofpermeable soil, brought down by erosion from the hill-sides, they wouldno longer hold water, and rice cultivation--the mainstay of Japan'sfood-supply--would be out of the question. For this reason the countryhas spent as much as ten times the capital value of eroding land on soilconservation work, mainly as an insurance for saving the valuable ricelands below. Thus in 1925 the Tokyo Forestry Board spent 453 yen(45 pounds) per acre in anti-erosion measures on a forest area, valued at40 yen per acre, in order to save rice-fields lower down valued at 240to 300 yen per acre.
The dangers from erosion have been recognized in Japan for centuries andan exemplary technique has been developed for preventing them. It is nowa definite part of national policy to maintain the upper regions of eachcatchment area under forest, as the most economical and effective methodof controlling flood waters and insuring the production of rice in thevalleys. For many years erosion control measures have formed animportant item in the national budget.
According to Lowdermilk, erosion control in Japan is like a game ofchess. The forest engineer, after studying his eroding valley, makes hisfirst move, locating and building one or more check dams. He waits tosee what Nature's response is. This determines the forest engineer'snext move, which may be another dam or two, an increase in the formerdam, or the construction of side retaining walls. After another pausefor observation, the next move is made and so on until erosion ischeckmated. The operation of natural forces, such as sedimentation andre-vegetation, are guided and used to the best advantage to keep downcosts and to obtain practical results. No more is attempted than Naturehas already done in the region. By 1919 nearly 2,000,000 hectares ofprotection forests were used in erosion control. These forest areas domore than control erosion. They help the soil to absorb and maintainlarge volumes of rain-water and to release it slowly to the rivers andsprings.
China, on the other hand, presents a very striking example of the evilswhich result from the inability of the administration to deal with thewhole of a great drainage unit. On the slopes of the upper reaches ofthe Yellow River extensive soil erosion is constantly going on. Everyyear the river transports over 2,000 million tons of soil, sufficient toraise an area of 400 square miles by 5 feet. This is provided by theeasily erodible loess soils of the upper reaches of the catchment area.The mud is deposited in the river bed lower down so that the embankmentswhich contain the stream have constantly to be raised. Periodically thegreat river wins in this unequal contest and destructive inundationsresult. The labour expended on the embankments is lost because thenature of the erosion problem as a whole has not been grasped, and thearea drained by the Yellow River has not been studied and dealt with asa single organism. The difficulty now is the over-population of theupper reaches of the catchment area, which prevents afforestation andlaying down to grass. Had the Chinese maintained effective control ofthe upper reaches--the real cause of the trouble--the erosion problem inall probability would have been solved long ago at a lesser cost inlabour than that which has been devoted to the embankment of the river.China, unfortunately, does not stand alone in this matter. A number ofother rivers, like the Mississippi, are suffering from overwork,followed by periodical floods as the result of the growth of soilerosion in the upper reaches.
Although the damage done by uncontrolled erosion all over the world isvery great, and the case for action needs no argument, neverthelessthere is one factor on the credit side which has been overlooked in therecent literature. A considerable amount of new soil is being constantlyproduced by natural weathering agencies from the sub-soil and the parentrock. This when suitably conserved will soon re-create large stretchesof valuable land. One of the best regions for the study of this questionis the black cotton soil of Central India, which overlies the basalt.Here, although erosion is continuous, the soil does not often disappearaltogether, for the reason that as the upper layers are removed by rain,fresh soil is re-formed from below. The large amount of earth soproduced is well seen in the Gwalior State, where the late Ruleremployed an irrigation officer, lent by the Government of India, toconstruct a number of embankments, each furnished with spillways, acrossmany of the valleys, which had suffered so badly by uncontrolledrain-wash in the past that they appeared to have no soil at all, thescrub vegetation just managing to survive in the crevices of the barerock. How great is the annual formation of new soil, even in suchunpromising circumstances, must be seen to be believed. In a very fewyears, the construction of embankments was followed by stretches offertile land which soon carried fine crops of wheat. A brief illustratedaccount of the work done by the late Maharaja of Gwalior would be ofgreat value at the moment for introducing a much needed note of optimismin the consideration of this soil erosion problem. Things are not quiteso hopeless as they are often made to appear.
Why is the forest such an effective agent in the prevention of soilerosion and in feeding the springs and rivers? The forest does twothings: (1) the trees and undergrowth break up the rainfall into finespray and the litter on the ground protects the soil from erosion; (2)the residues of the trees and animal life met with in all woodlands areconverted into humus, which is then absorbed by the soil underneath,increasing its porosity and water-holding power. The soil cover and thesoil humus together prevent erosion and at the same time store largevolumes of water. These factors--soil protection, soil porosity, andwater retention--conferred by the living forest cover, provide the keyto the solution of the soil erosion problem. All other purely mechanicalremedies such as terracing and drainage are secondary matters, althoughof course important in their proper place. The soil must have as muchcover as possible; it must be well stocked with humus so that it candrink in and retain the rainfall. It follows, therefore, that in theabsence of trees there must be a grass cover, some cover-crop, and ampleprovision for keeping up the supply of humus. Each field so providedsuffers little or no erosion. This confirms the view of Williams(Timiriasev Academy, Moscow) who, before erosion became important in theSoviet Union, advanced an hypothesis that the decay of pastcivilizations was due to a decline in soil fertility, consequent on thedestruction of the soil's crumb structure when the increasing demands ofcivilization necessitated the wholesale ploughing up of grass-land.Williams regarded grass as the basis of all agricultural landutilization and the soil's chief weapon against the plundering instinctsof humanity. His views are exerting a marked influence on soilconservation policy in the U.S.S.R. and indeed apply to many othercountries.
Grass is a valuable factor in the correct design and construction ofsurface drains. Whenever possible these should be wide, very shallow,and completely grassed over. The run-off then drains away as a thinsheet of clear water, leaving all the soil particles behind. The grassis thereby automatically manured and yields abundant fodder. This simpledevice was put into practice at the Shahjahanpur Sugar ExperimentStation in India. The earth service roads and paths were excavated sothat the level was a few inches below that of the cultivated area. Theywere then grassed over, becoming very effective drains in the rainyseason, carrying off the excess rainfall as clear water without any lossof soil.
If we regard erosion as the natural consequence of improper methods ofagriculture, and the catchment area of the river as the natural unit forthe application of soil conservation methods, the various remediesavailable fall into their proper place. The upper reaches of each riversystem must be afforested; cover crops including grass and leys must beused to protect the arable surface whenever possible; the humus contentof the soil must be increased and the crumb structure restored so thateach field can drink in its own rainfall; over-stocking and over-grazingmust be prevented; simple mechanical methods for conserving the soil andregulating the run-off, like terracing, contour cultivation and contourdrains, must be utilized. There is, of course, no single anti-erosiondevice which can be universally adopted. The problem must, in the natureof things, be a local one. Nevertheless, certain guiding principlesexist which apply everywhere. First and foremost is the restoration andmaintenance of soil fertility, so that each acre of the catchment areacan do its duty by absorbing its share of the rainfall.
THE FORMATION OF ALKALI LANDS
When the land is continuously deprived of oxygen the plant is soonunable to make use of it: a condition of permanent infertility results.
In many parts of the tropics and sub-tropics agriculture is interferedwith by accumulations of soluble salts composed of various mixtures ofthe sulphate, chloride, and carbonate of sodium. Such areas are known asalkali lands. When the alkali phase is still in the mild or incipientstage, crop production becomes difficult and care has to be taken toprevent matters from getting worse. When the condition is fullyestablished, the soil dies; crop production is then out of the question.Alkali lands are common in Central Asia, India, Persia, Iraq, Egypt,North Africa, and the United States.
At one period it was supposed that alkali soils were the naturalconsequences of a light rainfall, insufficient to wash out of the landthe salts which always form in it by progressive weathering of the rockpowder of which all soils largely consist. Hence alkali lands wereconsidered to be a natural feature of arid tracts, such as parts ofnorth-west India, Iraq, and northern Africa, where the rainfall is verysmall. Such ideas on the origin and occurrence of alkali lands do notcorrespond with the facts and are quite misleading. The rainfall of theProvince of Oudh, in India, for example, where large stretches of alkalilands naturally occur, is certainly adequate to dissolve thecomparatively small quantities of soluble salts found in these infertileareas, if their removal were a question of sufficient water only. InNorth Bihar the average rainfall, in the sub-montane tracts where largealkali patches are common, is about 50 to 60 inches a year. Aridconditions, therefore, are not essential for the production of alkalisoils; heavy rainfall does not always remove them. What is a necessarycondition is impermeability. In India whenever the land loses itsporosity, by the constant surface irrigation of stiff soils with atendency to impermeability, by the accumulation of stagnant subsoilwater, or through some interference with the surface drainage, alkalisalts sooner or later appear. Almost any agency, even overcultivationand over-stimulation by means of artificial manures, both of whichoxidize the organic matter and slowly destroy the crumb structure, willproduce alkali land. In the neighbourhood of Pusa in North Bihar, oldroads and the sites of bamboo clumps and of certain trees such as thetamarind (Tamarindus indica L.) and the pipul (Ficus religiosa L.),always give rise to alkali patches when they are brought intocultivation. The densely packed soil of such areas invariably shows thebluish-green markings which are associated with the activities of thosesoil organisms which live in badly aerated soils without a supply offree oxygen. A few inches below the alkali patches, which occur on thestiff loess soils of the Quetta Valley, similar bluish-green and brownmarkings always occur. In the alkali zone in North Bihar, wells havealways to be left open to the air, otherwise the water is contaminatedby sulphuretted hydrogen, thereby indicating a well-marked reductivephase in the deeper layers. In a sub-soil drainage experiment on theblack soils of the Nira valley in Bombay where perennial irrigation wasfollowed by the formation of alkali land, Mann and Tamhane found thatthe salt water which ran out of these drains soon smelt strongly ofsulphuretted hydrogen, and a white deposit of sulphur was formed at themouth of each drain, proving how strong were the reducing actions inthis soil. Here the reductive phase in alkali formation wasunconsciously demonstrated in an area where alkali salts were unknownuntil the land was water-logged by over-irrigation and the oxygen-supplyof the soil was restricted.
The view that the origin of alkali land is bound up with defective soilaeration is supported by the recent work on the origin of saltwaterlakes in Siberia. In Lake Szira-Kul, between Bateni and the mountainrange of Kizill Kaya, Ossendowski observed in the black ooze taken fromthe bottom of the lake and in the water a certain distance from thesurface an immense network of colonies of sulphur bacilli which gave offlarge quantities of sulphuretted hydrogen and so destroyed practicallyall the fish in this lake. The great water basins in Central Asia arebeing metamorphosed in a similar way into useless reservoirs of saltwater, smelling strongly of hydrogen sulphide. In the limans near Odessaand in portions of the Black Sea, a similar process is taking place. Thefish, sensing the change, are slowly leaving this sea as the layers ofwater, poisoned by sulphuretted hydrogen, are gradually rising towardsthe surface. The death of the lakes scattered over the immense plains ofAsia and the destruction of the impermeable soils of this continent fromalkali salt formation are both due to the same primary cause--intenseoxygen starvation. Often this oxygen starvation occurs naturally; inother cases it follows perennial irrigation.
The stages in the development of the alkali condition are somewhat asfollows. The first condition is an impermeable soil. Such soils--theusar plains of northern India for example--occur naturally where theclimatic conditions favour those biological and physical factors whichdestroy the soil structure by disintegrating the compound particles intotheir ultimate units. These latter are so extremely minute and souniform in size that they form with water a mixture possessing some ofthe properties of colloids which, when dry, pack into a hard dry mass,practically impermeable to water and very difficult to break up. Suchsoils are very old. They have always been impermeable and have nevercome into cultivation.
In addition to the alkali tracts which occur naturally a number are incourse of formation as the result of errors in soil management, thechief of which are:
(a) The excessive use of irrigation water. This gradually destroys thebinding power of the organic cementing matter which glues the soilparticles together, and displaces the soil air. Anaerobic changes,indicated by blue and brownish markings, first occur in the lower layersand finally lead to the death of the soil. It is this slow destructionof the living soil that must be prevented if the existing schemes ofperennial irrigation are to survive. The process is taking place beforeour eyes to-day in the Canal Colonies of India where irrigation isloosely controlled.
(b) Over-cultivation without due attention to the replenishment ofhumus. In those continental areas like the Indo-Gangetic plain, wherethe risk of alkali is greatest, the normal soils contain only a smallreserve of humus, because the biological processes which consume organicmatter are very intense at certain seasons due to sudden changes fromlow to very high temperatures and from intensely dry weather to periodsof moist tropical conditions. Accumulations of organic matter such asoccur in temperate zones are impossible. There is, therefore, a verysmall margin of safety. The slightest errors in soil management will notonly destroy the small reserve of humus in the soil but also the organiccement on which the compound soil particles and the crumb structuredepend.
The result is impermeability, the first stage in the formation of alkalisalts.
(c) The use of artificial manures, particularly sulphate of ammonia. Thepresence of additional combined nitrogen in an easily assimilable formstimulates the growth of fungi and other organisms which, in the searchfor the organic matter needed for energy and for building up microbialtissue, use up first the reserve of soil humus and then the moreresistant organic matter which cements the soil particles. Ordinarilythis glue is not affected by the processes going on in a normallycultivated soil, but it cannot withstand the same processes whenstimulated by dressings of artificial manures.
Alkali land therefore starts with a soil in which the oxygen-supply ispermanently cut off. Matters then go from bad to worse very rapidly. Allthe oxidation factors which are essential for maintaining a healthy soilcease. A new soil flora--composed of anaerobic organisms which obtaintheir oxygen from the substratum--is established. A reduction phaseensues. The easiest source of oxygen--the nitrates--is soon exhausted.The organic matter then undergoes anaerobic fermentation. Sulphurettedhydrogen is produced as the soil dies, just as in the lakes of CentralAsia. The final result of the chemical changes that take place is theaccumulation of the soluble salts of alkali land--the sulphate,chloride, and carbonate of sodium. When these salts are present ininjurious amounts they appear on the surface in the form of snow-whiteand brownish-black incrustations. The former (white alkali) consistslargely of the sulphate and chloride of sodium, and the latter (thedreaded black alkali) contains sodium carbonate in addition and owes itsdark colour to the fact that this salt is able to dissolve the organicmatter in the soil and produce physical conditions which render drainageimpossible. According to Hilgard, sodium carbonate is formed from thesulphate and chloride in the presence of carbon dioxide and water. Theaction is reversed in the presence of oxygen. Subsequent investigationshave modified this view and have shown that the formation of sodiumcarbonate in soil takes place in stages. The appearance of this saltalways marks the end of the chapter. The soil is dead. Reclamation thenbecomes difficult on account of the physical conditions set up by thesealkali salts and the dissolved organic matter.
The occurrence of alkali land, as would be expected from its origin, isextremely irregular. When ordinary alluvial soils like those of thePunjab and Sind are brought under perennial irrigation, small patches ofalkali first appear where the soil is heavy; on stiffer areas thepatches are large and tend to run together. On open permeable stretches,on the other hand, there is no alkali. In tracts like the WesternDistricts of the United Provinces, where irrigation has been the rulefor a long period, zones of well-aerated land carrying fine irrigatedcrops occur alongside the barren alkali tracts. Iraq also furnishesinteresting examples of the connexion between alkali and poor soilaeration. Intensive cultivation under irrigation is only met with inthat country where the soils are permeable and the natural drainage isgood. Where the drainage and aeration are poor, the alkali condition atonce becomes acute. There are, of course, a number of irrigationschemes, such as the staircase cultivation of the Hunzas in northwestIndia and of Peru, where the land has been continually watered from timeimmemorial without any development of alkali salts. In Italy andSwitzerland perennial irrigation has been practiced for long periodswithout harm to the soil. In all such cases, however, careful attentionhas been paid to drainage and aeration and to the maintenance of humus;the soil processes have been confined by Nature or by man to theoxidative phase; the cement of the compound particles has been protectedby keeping up a sufficiency of organic matter.
Every possible gradation in alkali land is met with. Minute quantitiesof alkali salts in the soil have no injurious effect on crops or on thesoil organisms. It is only when the proportion increases beyond acertain limit that they first interfere with growth and finally preventit altogether. Leguminous crops are particularly sensitive to alkaliespecially when this contains carbonate of soda. The action of alkalisalts on the plant is a physical one and depends on the osmotic pressureof solutions, which increases with the amount of the dissolvedsubstance. For water to pass readily from the soil into the roots ofplants, the osmotic pressure of the cells of the root must beconsiderably greater than that of the soil solution outside. If the soilsolution became stronger than that of the cells, water would passbackwards from the roots to the soil and the crops would dry up. Thisstate of affairs naturally occurs when the soil becomes charged withalkali salts beyond a certain point. The crops are then unable to takeup water and death results. The roots behave like a plump strawberrywhen placed in a strong solution of sugar. Like the strawberry theyshrink in size because they have lost water to the stronger solutionoutside. Too much salt in the water therefore makes irrigation wateruseless and destroys the canal as a commercial proposition.
The reaction of the crop to the first stages in alkali production isinteresting. For twenty years at Pusa and eight years in the QuettaValley I had to farm land, some of which hovered, as it were, on theverge of alkali. The first indication of the condition is a darkening ofthe foliage and the slowing down of growth. Attention to soil aeration,to the supply of organic matter, and to the use of deep-rooting cropslike lucerne and pigeon pea, which break up the sub-soil, soon setsmatters right. Disregard of Nature's danger signals, however, leads totrouble--a definite alkali patch is formed. When cotton is grown undercanal irrigation on the alluvial soils of the Punjab, the reaction ofthe plant to incipient alkali is first shown by the failure to set seed,on account of the fact that the anther, the most sensitive portion ofthe flower, fails to function and to liberate its pollen. The cottonplant naturally finds it difficult to obtain from mild alkali soil allthe water it needs--this shortage is instantly reflected in thebreakdown of the floral mechanism.
The theory of the reclamation of alkali land is very simple. All that isneeded, after treating the soil with sufficient gypsum (which transformsthe sodium clays into calcium clays), is to wash out the soluble salts,to add organic matter, and then to farm the land properly. Suchreclaimed soils are then exceedingly fertile and remain so. Ifsufficient water is available it is sometimes possible to reclaim alkalisoils by washing only. I once confirmed this. The berm of a raised waterchannel at the Quetta Experiment Station was faced with rather heavysoil from an alkali patch. The constant passage of the irrigation waterdown the water channel soon removed the alkali salts. This soil thenproduced some of the heaviest crops of grass I have ever seen in thetropics. When, however, the attempt is made to reclaim alkali areas on afield scale, by flooding and draining, difficulties at once arise unlesssteps are taken first to replace all the sodium in the soil complex bycalcium and then to prevent the further formation of sodium clays. Evenwhen these reclamation methods succeed, the cost is always considerable;it soon becomes prohibitive; the game is not worth the candle. Theremoval of the alkali salts is only the first step; large quantities oforganic matter are then needed; adequate soil aeration must be provided;the greatest care must be taken to preserve these reclaimed soils and tosee that no reversion to the alkali condition occurs. It is exceedinglyeasy under canal irrigation to create alkali salts on certain areas. Itis exceedingly difficult to reverse the process and to transform alkaliland back again into a fertile soil.
Nature has provided, in the shape of alkali salts, a very effectivecensorship for all schemes of perennial irrigation. The conquest of thedesert, by means of the canal, by no means depends on the mere provisionof water and arrangements for the periodical flooding of the surface.This is only one of the factors of the problem. The water must be usedin such a manner and the soil management must be such that the fertilityof the soil is maintained intact. There is obviously no point increating, at vast expense, a Canal Colony and producing crops for ageneration or two, followed by a desert of alkali land. Such anachievement merely provides another example of agricultural banditry. Itmust always be remembered that the ancient irrigators never developedany efficient method of perennial irrigation, but were content with thebasin system, a device by which irrigation and soil aeration can becombined. (The land is embanked; watered once; when dry enough it iscultivated and sown. In this way water can be provided without anyinterference with soil aeration.) In his studies on irrigation anddrainage, King concludes an interesting discussion of this question inthe following words, which deserve the fullest consideration on the partof the irrigation authorities all over the world:
'It is a noteworthy fact that the excessive development of alkalis inIndia, as well as in Egypt and California, is the result of irrigationpractices modern in their origin and modes and instituted by peoplelacking in the traditions of the ancient irrigators, who had workedthese same lands thousands of years before. The alkali lands of to-day,in their intense form, are of modern origin, due to practices which areevidently inadmissible, and which in all probability were known to beso by the people whom our modern civilization has supplanted.'
GORRIE, R. M. 'The Problem of Soil Erosion in the British Empire,with special reference to India', Journal of the Royal Societyof Arts, lxxxvi, 1938, p. 901.
HOWARD, SIR ALBERT. 'A Note on the Problem of Soil Erosion', Journalof the Royal Society of Arts, lxxxvi, 1938, p.926.
JACKS, G. V., and WHYTE, R. O. Erosion and Soil Conservation, Bulletin 25,Imperial Bureau of Pastures and Forage Crops, Aberystwyth, 1938.
------The Rape of the Earth: A World Survey of Soil Erosion, London, 1939.
Soils and Men, Year Book of Agriculture, 1938, U.S. Dept. of Agr.,Washington, D.C., 1938.
HILGARD, E. W. Soils, New York, 1906.
HOWARD, A. Crop Production in India, Oxford University Press, 1924.
KING, F. H. Irrigation and Drainage, London, 1900.
OSSENDOWSKI, F. Man and Mystery in Asia, London, 1924.
RUSSELL, SIR JOHN. Soil Conditions and Plant Growth, London, 1937.
THE RETREAT OF THE CROP AND THE ANIMAL BEFORE THE PARASITE
In the previous chapter we have seen how Nature, by means of soilerosion, removes any area of worn-out land and recreates new soil in afresh place. Mismanagement of the land is followed later on by a NewDeal, as it were, somewhere else. A similar rule applies to crops: thediseased crop is quietly but effectively labelled prior to removal forthe manufacture of humus, so that the next generation of plants maybenefit.
Mother earth has provided a vast organization for indicating theinefficient crop. Where the soil is infertile, where an unsuitablevariety is being grown, or where some mistake has been made inmanagement, Nature at once registers her disapproval through herCensors' Department. One or more of the groups of parasitic insects andfungi--the organisms which thrive on unhealthy living matter--are toldoff to point out that farming has failed. In the conventional languageof to-day the crop is attacked by disease. In the writings of thespecialist, a case has arisen for the control of a pest: a crop must beprotected.
In recent years another form of disease--known as virus disease--hasmade its appearance. There is no obvious parasite in virus diseases, butinsects among other agencies are able to transmit the trouble fromdiseased to apparently healthy plants in the neighbourhood. When thecell contents of affected plants are examined, the proteins exhibitdefinite abnormalities, thereby suggesting that the work of the greenleaf is not effective; the synthesis of albuminoids seems to beincomplete. With the development of special research laboratories, likethat at Cambridge, more and more of these diseases are being discoveredand a considerable literature on the subject has arisen.
The virus diseases do not complete the story. A certain number ofmaladies occur in which the apparent cause is neither a fungus, aninsect, nor a virus. These are grouped under the generaltitle--physiological diseases: troubles arising from the collapse of thenormal metabolic processes.
How has agricultural science dealt with the diseases of crops? Theanswer is both interesting and illuminating. The subject has beenapproached in a variety of ways, which can be briefly summed up underthe following four heads:
1. The study of the life history of the pest, including the generalrelation of the parasite to the crop and the influence of theenvironment on the struggle for supremacy between the two. The mainobject of these investigations has been to discover some possibleweakness in the life history of the pest which can be utilized todestroy it or to protect the plant from infection. An impressive volumeof specialist literature has resulted. As the number of investigatorsgrows and as their inquiries become more exhaustive and tend to cover arapidly increasing proportion of the earth's surface, there is acorresponding increase in the volume of print. It is now almostimpossible to take up any of the periodicals dealing with agriculturalresearch without finding at least one long illustrated articledescribing some new disease. So vast has the literature become that thespecialists themselves are unable to cope with it. Most of it can onlybe read by the workers in abstract, for which again new agencies havebeen created in the British Empire--the Imperial Bureaux of Entomologyand Mycology--bodies which act as clearing-houses of information anddeal with the published papers in a way reminiscent of the methods ofthe Banker's Clearing House in dealing with cheques.
2. The study of the natural parasites of insect pests, the breeding ofthese animals, and their actual introduction whenever this procedurepromises success. A separate institution for this purpose has beenfounded at Farnham Royal in Buckinghamshire.
3. The protection of the crop from the inroads of the parasite. As arule this takes two forms: (1) the discovery of insecticides andfungicides and the design of the necessary machinery for covering thecrop with a thin film of poison which will destroy the parasite in theresting stage or before it can gain entry to the host; (2) thedestruction of the parasite by burning, by the use of corrosive liquidslike strong sulphuric acid, or by germicides added to the soil so thatthe amount of infecting material will be negligible.
4. The framing and conduct of regulations to protect an area from someforeign pest which has not yet made its appearance. These follow theusual methods of quarantine. Importation of plants and seeds isprohibited altogether, introduction is permitted under licence, or theplant material is inspected and fumigated at the port of entry. Theprinciple in all cases is the same--the crops must be protected fromchance infection by some foreign parasite which might cause untolddamage. As traffic by land, sea, and air grows in volume and becomesspeeded up, it will be increasingly difficult to enforce theseregulations. It is impossible even now to inspect all luggage and allmerchandise and to prevent the smuggling of small packets of seed orcuttings of living plants. Indeed, if an investigation were to be madeof the personal effects of the coolies passing backwards and forwardsbetween India and Burma, India and the Federated Malay States andCeylon, it would be seen what an extraordinary collection of articlesthese men and women carry about and how frequently plants and seeds areincluded. Enthusiasts in gardening often collect plants on their travelswhich interest them. The population, live stock, and factories of GreatBritain are partly supplied with seeds from all over the world. By oneor other of these agencies a few new pests are almost certain from timeto time to enter the country. These quarantine methods therefore cannever succeed.
More than fifty years have passed since the modern work on the diseasesof plants first began. What has been the general result of all thisstudy of vegetable pathology? Has it provided anything of permanentvalue to agriculture? Is the game worth the candle? Must agriculturalscience go on discovering more and more new pests and devising more andmore poison sprays to destroy them or is there any alternative method ofdealing with the situation? Why is there so much of this disease? Canthe growing tale of the pests of Western agriculture be accounted for bysome subtle change in practice? Can the cultivators of the East, forexample, teach us anything about diseases and their control?
In this chapter an attempt will be made to answer these interestingquestions.
It is a well-understood principle in business that any organization likeagricultural research, which has grown by accretion rather than by thedevelopment of a considered plan, stands in need of a periodicalcritical examination to ascertain whether the results obtainedcorrespond with the cost and whether any modifications are needed in thelight of new knowledge and experience. I began such an investigation ofthe plant and animal disease section of agricultural science in 1899 andhave steadily pursued it since. After forty years' work I feelsufficiently confident of my general conclusions to place them onrecord, and to ask for them to be considered on their merits.
I took up research in agriculture as a mycologist in the West Indies in1899, where I specialized in the diseases of sugar-cane and cacao andbecame interested in tropical agriculture. Almost at once I discerned afundamental weakness in the research organization: the mycologist had noland on which he could take his own advice about remedies before askingplanters to adopt them.
My next post was botanist at Wye College in Kent, where I was in chargeof the experiments on hops and had ample opportunities for studying theinsect and fungous diseases of this interesting crop. But again I had noland on which I could try out certain ideas that were fermenting in mymind about the prevention of hop diseases. I observed one interestingthing: the increase in the resisting power to infection of the young hopflower which resulted from pollination. This observation has sincebrought about a change in the local practice: the male hop is nowcultivated and ample pollination of the female flowers--the hops ofcommerce--occurs.
In 1905 I was appointed Imperial Economic Botanist to the Government ofIndia. At the Pusa Agricultural Research Institute, largely through thesupport of the Director, the late Mr. Bernard Coventry, I had for thefirst time all the essentials for work--interesting problems, money,freedom, and, last but nit least, 75 acres of land on which I could growcrops in my own way and study their reaction to insect and fungous pestsand other things. My real training in agricultural research thenbegan--six years after leaving the University and obtaining all thepaper qualifications and academic experience then needed by aninvestigator.
At the beginning of this second and intensive phase of my training, Iresolved to break new ground and try out an idea (which first occurredto me in the West Indies), namely, to observe what happened when insectand fungous diseases were left alone and allowed to develop unchecked,and where indirect methods only, such as improved cultivation and moreefficient varieties, were employed to prevent attack. This point of viewderived considerable impetus from a preliminary study of Indianagriculture. The crops grown by the cultivators in the neighbourhood ofPusa were remarkably free from pests of all kinds; such things asinsecticides and fungicides found no place in this ancient system ofagriculture. I decided that I could not do better than watch theoperations of these peasants, and acquire their traditional knowledge asrapidly as possible. For the time being, therefore, I regarded them asmy professors of agriculture. Another group of instructors wereobviously the insects and fungi themselves. The methods of thecultivators if followed would result in crops practically free fromdisease; the insects and fungi would be useful for pointing outunsuitable varieties and methods of farming inappropriate to thelocality.
It was possible for me to approach the subject of plant diseases in thisunorthodox manner for two reasons. In the first place the AgriculturalResearch Institute at Pusa was little more than a name when I arrived inIndia in 1905. Everything was fluid; there was nothing in the nature ofan organized system of research in existence. In the second place, myduties, fortunately for me, had not been clearly defined. I wastherefore able to break new ground, to widen the scope of economicbotany until it became crop production, to base my investigations on afirst-hand knowledge of Indian agriculture, and to take my own advicebefore offering it to other people. In this way I escaped the fate ofthe majority of agricultural investigators--the life of a laboratoryhermit devoted to the service of an obsolete research organization.Instead, I spent my first five years in India ascertaining by practicalexperience the principles underlying health in crops.
In order to give my crops every chance of being attacked by parasites,nothing was done in the way of prevention; no insecticides andfungicides were used; no diseased material was ever destroyed. As myunderstanding of Indian agriculture progressed, and as my practiceimproved, a marked diminution of disease occurred. At the end of fiveyears' tuition under my new professors--the peasants and the pests--theattacks of insects and fungi on all crops, whose root systems weresuitable to the local soil conditions, became negligible. By 1910 I hadlearnt how to grow healthy crops, practically free from disease, withoutthe slightest help from mycologists, entomologists, bacteriologists,agricultural chemists, statisticians, clearing-houses of information,artificial manures, spraying machines, insecticides, fungicides,germicides, and all the other expensive paraphernalia of the modernExperiment Station.
I then posed to myself the principles which appeared to underlie thediseases of plants:
1. Insects and fungi are not the real cause of plant diseases but onlyattack unsuitable varieties or crops imperfectly grown. Their true roleis that of censors for pointing out the crops that are improperlynourished and so keeping our agriculture up to the mark. In other words,the pests must be looked upon as Nature's professors of agriculture: asan integral portion of any rational system of farming.
2. The policy of protecting crops from pests by means of sprays,powders, and so forth is unscientific and unsound as, even whensuccessful, such procedure merely preserves the unfit and obscures thereal problem--how to grow healthy crops.
3. The burning of diseased plants seems to be the unnecessarydestruction of organic matter as no such provision as this exists inNature, in which insects and fungi after all live and work.
This preliminary exploration of the ground suggested that the birthrightof every crop is health, and that the correct method of dealing withdisease at an Experiment Station is not to destroy the parasite, but tomake use of it for tuning up agricultural practice.
Steps were then taken to apply these principles to oxen, the power unitin Indian agriculture. For this purpose it was necessary to have thework cattle under my own charge, to design their accommodation, and toarrange for their feeding, hygiene, and management. At first this wasrefused, but after persistent importunity, backed by the powerfulsupport of the Member of the Viceroy's Council in charge of agriculture(the late Sir Robert Carlyle, K.C.S.I.), I was allowed to have charge ofsix pairs of oxen. I had little to learn in this matter as I belong toan old agricultural family and was brought up on a farm which had madefor itself a local reputation in the management of cattle. My workanimals were most carefully selected and everything was done to providethem with suitable housing and with fresh green fodder, silage, andgrain, all produced from fertile land. I was naturally intenselyinterested in watching the reaction of these well-chosen and well-fedoxen to diseases like rinderpest, septicaemia, and foot-and-mouthdisease which frequently devastated the countryside. These epidemics arethe result of starvation, due to the intense pressure of the bovinepopulation on the limited food-supply. None of my animals weresegregated; none were inoculated; they frequently came in contact withdiseased stock. As my small farm-yard at Pusa was only separated by alow hedge from one of the large cattle-sheds on the Pusa estate, inwhich outbreaks of foot-and-mouth disease often occurred, I have severaltimes seen my oxen rubbing noses with foot-and-mouth cases. Nothinghappened. The healthy well-fed animals reacted to this disease exactlyas suitable varieties of crops, when properly grown, did to insect andfungous pests--no infection took place.
As the factors of time and place are important when testing anyagricultural innovation, it now became necessary to try out the threeprinciples referred to above over a reasonably long period and in newlocalities. This was done during the next twenty-one years at threecentres: Pusa (1910-24), Quetta (summers of 1910-18), and Indore(1924-31).
At Pusa, during the years 1910 to 1924, outbreaks of plant diseases wererare, except on certain cultures with deep root systems which were grownchiefly to provide a supply of infecting material for testing thedisease resistance of new types obtained by plant-breeding methods. Poorsoil aeration always encouraged disease at Pusa. The unit species ofLathyras sativus provided perhaps the most interesting example of theconnexion between soil aeration and insect attack. These unit speciesfell into three groups: surface-rooted types always immune to green-fly;deep-rooted types always heavily infected; types with intermediate rootsystem always moderately infected. These sets of cultures were grownside by side year after year in small oblong plots about 10 feet wide.The green-fly infection repeated itself each year and was determined notby the presence of the parasite, but by the root development of thehost. Obviously the host had to be in a certain condition beforeinfection could take place. The insect, therefore, was not the cause butthe consequence of something else.
One of the crops under study at Pusa was tobacco. At first a great manymalformed plants--since proved to be due to virus--made their appearancein my cultures. When care was devoted to the details of growing tobaccoseed, to the raising of the seedlings in the nurseries, to transplantingand general soil management, this virus disease disappeared altogether.It was very common during the first three years; it then becameinfrequent; between 1910 and 1924 I never saw a single case. Nothing wasdone in the way of prevention beyond good farming methods and thebuilding up of a fertile soil. I dismissed it at the time as one of themany mare's nests of agricultural science--things which have no realexistence.
For a period of eight years, I was provided with a subsidiary experimentstation on the loess soils of the Quetta valley for the study of theproblems underlying fruit-growing and irrigation. I observed no fungousdisease of any importance in the dry climate of the Quetta valley duringthe eight summers I spent there. In the grape gardens, run by thetribesmen on the well-drained slopes of the valley, I never observed anydiseases--insect or fungous--on the grapes or on the vines, althoughthey were planted on the floors of deep trenches, allowed to climb upthe earth walls and were frequently irrigated. At first sight, all theconditions for mildew seemed to have been provided, yet I never saw asingle speck. Three favourable factors probably accounted for thisresult. The climate was exceedingly dry, with considerable air movementand cloudless skies; the soil made use of by the roots of the vine wasopen, well drained, and exceptionally well aerated; the only manure usedwas farm-yard manure. Growth, yield, quality, and disease resistanceleft nothing to be desired.
The chief pest of fruit-trees at Quetta was green-fly soon after theyoung leaves appeared. This could be produced or avoided at will bycareful attention to cultivation and irrigation. Any interference withsoil aeration brought on this trouble; anything which promoted soilaeration prevented it. I frequently produced a strong attack ofgreen-fly on peaches and almonds by over-irrigation during the winterand spring, and then stopped it dead by deep cultivation. The youngshoots were covered with the pest below, but the upper portions of thesame shoots were completely healthy. The green-fly never spread from thelower to the upper leaves on the same twig. The tribesmen got over thetendency of these loess soils to pack under irrigation in a very simpleway. Lucerne was always grown in the fruit orchards, and regularlytop-dressed with farm-yard manure. In this way the porosity of the soilwas maintained and the green-fly kept in check.
At the Institute of Plant Industry, Indore, only two cases of diseaseoccurred during the eight years I was there. The first occurred on asmall field of gram (Cicer arietinum), about two-thirds of which wasflooded for a few days one July, due to the temporary stoppage of one ofthe drainage canals which took storm water from adjacent areas throughthe estate. A map of the flooded area was made at the time. In October,about a month after sowing, this plot was heavily attacked by the gramcaterpillar, the insectinfected area corresponding exactly with theinundation area. The rest of the plot escaped infection and grewnormally. The insect did not spread to the other 50 acres of gram grownthat year alongside. Some change in the food of the caterpillar hadobviously been brought about by the alteration in the soil conditionscaused by the temporary flooding. The second case of disease occurred ina field of san hemp (Crotalaria juncea L.) intended for green-manuring;however, this was not ploughed in but was kept for seed. After floweringthe crop was smothered by a mildew; no seed was harvested. To produce acrop of seed of san on the black soils, it is necessary to manure theland with humus or farm-yard manure, when no infection takes place andan excellent crop of seed is obtained.
One experiment with cotton unfortunately could not be arranged in spiteof all my efforts. At Indore there was a remarkable absence of allinsect and fungous diseases of cotton. Good soil management, combinedwith dressings of humus, produced crops which were practically immune toall the pests of cotton. When the question of protecting India from thevarious cotton boll-worms and boll-weevils from America was discussed, Ioffered to have these let loose among my cotton cultures at Indore inorder (1) to settle the question whether these troubles in the U.S.A.were due to the insect or to the way the cotton was grown, and (2) tosubject my farming methods to a crucial test. I am pretty certain theinsects would have found my cotton cultures very indifferentnourishment. My proposal, however, did not find favour with theentomological advisers of the Indian Cotton Committee and the matterdropped.
At Quetta and Indore there was no case of infectious disease among theoxen. The freedom from disease observed at Pusa was again experienced inthe new localities--the Western Frontier and Central India.
It was soon discovered in the course of this work that the thing thatmatters most in crop production is a regular supply of well-madefarm-yard manure and that the maintenance of soil fertility is the basisof health.
HUMUS AND DISEASE RESISTANCE
Even on the Experiment Stations the supply of farm-yard manure wasalways insufficient. The problem was how to increase it in a countrywhere a good deal of the cattle-dung has to be burnt for fuel. Thesolution of this problem was suggested by the age-long practices ofChina. It involved the study of how best to convert the animal andvegetable wastes into humus, so that every holding in India could becomeself-supporting as regards manure. Such a problem did not fall within mysphere of work--the improvement of crops. It obviously necessitated agreat deal of chemical work under my personal control. The organizationof research at Pusa had gradually become more rigid; the old latitudewhich existed in the early days became a memory. That essential freedom,without which no progress is possible, had been gradually destroyed bythe growth of a research organization based on fragments of sciencerather than on the practical problems which needed investigation. Theinstrument became more important than its purpose. Such organizationscan only achieve their own destruction. This was the reason why Idecided to leave Pusa and found a new centre where I should be free tofollow the gleam unhampered and undisturbed. After a delay of six years,1918 to 1924, the Indore Institute was founded. In due course a simplemethod, known as the Indore Process, of composting vegetable and animalwastes was devised, tested, and tried out on the 300 acres of land atthe disposal of the Institute of Plant Industry, Indore. In a few yearsproduction more than doubled: the crops were to all intents and purposesimmune from disease.
Since 1931 steps have been taken to get the Indore Process taken up in anumber of countries, especially by the plantation industries such ascoffee, tea, sugar, sisal, maize, cotton, tobacco, and rubber. Theresults obtained have already been discussed. In all these trials theconversion of vegetable and animal wastes into humus has been followedby a definite improvement in the health of the crops and of the livestock. My personal experience in India has been repeated all over theworld. At the same time a number of interesting problems have beenunearthed. One example will suffice. In Rhodesia humus protects themaize crop from the attacks of the witchweed (Striga lutea). Is thisinfestation a consequence of malnutrition? Is immunity conferred by theestablishment of the mycorrhizal association? Answers to these questionswould advance our knowledge and would suggest a number of fascinatingproblems for investigation.
THE MYCORRHIZAL ASSOCIATION AND DISEASE
Why is humus such an important factor in the health of the crop? Themycorrhizal association provides the clue. The steps by which thisconclusion was reached in the case of tea have already been stated.
This association is not confined to one particular forest crop. Itoccurs in most if not all our cultivated plants. During 1938 Dr. Raynerand Dr. Levisohn examined and reported on a large number of mysamples--rubber, coffee, cacao, leguminous shade trees, green-manurecrops, coco-nuts, lung, cardamons, vine, banana, cotton, sugar-cane,hops, strawberries, bulbs, grasses and clovers and so forth. In all ofthese the mycorrhizal association occurs. It is probably universal. Weappear to be dealing with a very remarkable example of symbiosis inwhich certain soil fungi directly connect the humus in the soil with theroots of the crop. This fungous tissue may contain as much as 10 percent. of nitrogen in the form of protein, which is digested in theactive roots and probably carried by the transpiration current to theseat of carbon assimilation in the green leaves. Its effective presencein the roots of the plant is associated with health; its absence isassociated with diminished resistance to disease. Clearly the first stepin investigating any plant disease in the future will be to see that thesoil is fertile and that this fungous association is in full workingorder. If it is as important as is now suggested, there will be a markedimprovement in the behaviour of the host once the fertility of the soilis restored. If it has no significance, a fertile soil will make nodifference.
I have just obtained confirmatory results which prove how importanthumus is in helping a mycorrhiza-former--the apple--to throw offdisease. In 1935 I began the restoration, by means of humus, of my owngarden, the soil of which was completely worn-out when I acquired it inthe summer of 1934. The apple trees were literally smothered withAmerican blight, green-fly, and fruit-destroying caterpillars like thecodlin moth. The quality of the fruit was poor. Nothing was done tocontrol these pests beyond the gradual building up of the humus contentof the soil. In three years the parasites disappeared; the trees weretransformed; the foliage and the new wood now leave nothing to bedesired; the quality of the fruit is first class. These trees will nowbe used for infection experiments in order to ascertain whether thefertility of the soil has been completely restored or not. The reactionof the trees to the various pests of the apple will answer thisquestion. No soil analysis can tell me as much as the trees will.
The meaning of all this is clear. Nature has provided a marvellous pieceof machinery for conferring disease-resistance on the crop. Thismachinery is only active in soil rich in humus; it is inactive or absentin infertile land and in similar soils manured with chemicals. The fuelneeded to keep this machinery in motion is a regular supply of freshlyprepared humus, properly made. Fertile soils then yield crops resistantto disease. Worn-out soils, even when stimulated with chemical manures,result in produce which needs the assistance of insecticides andfungicides to yield a crop at all. These in broad outline are the facts.
The complete scientific explanation of the working of this remarkableexample of symbiosis remains to be provided. It would appear that in themycorrhizal association Nature has given us a mechanism far moreimportant and far more universal than the nodules on the roots of theclover family. It reconciles at one bound science and the age-longexperience of the tillers of the soil as to the supreme importance ofhumus. There has always been a mental reservation on the part of thebest farmers as to the value of artificial manures compared with goodold-fashioned muck. The effect of the two on the soil and on the crop isnever quite the same. Further, there is a growing conviction that theincrease in plant and animal diseases is somehow connected with the useof artificials. In the old days of mixed farming the spraying machinewas unknown, the toll taken by troubles like foot-and-mouth disease wasinsignificant compared with what it is now. The clue to all thesedifferences--the mycorrhizal association--has been there all the time.It was not realized because the experiment stations have blindlyfollowed the fashion set by Liebig and Rothamsted in thinking only ofsoil nutrients and have forgotten to look at the way the plant and thesoil come into gear. An attempt has been made to apply science to abiological problem by means of one fragment of knowledge only.
THE INVESTIGATIONS OF TO-MORROW
The next step in this investigation is to test the soundness of theviews put forward. This has been started by composting diseased materialand then using the humus to grow another crop on the same land. Diseasedtomatoes have been converted into humus by one of the large growers inthe south of England and the compost has been used to grow a second cropin the same greenhouses. No infection occurred.
The final proof that insects, fungi, viruses and so forth are not thecause of disease will be provided when the infection experiments ofto-morrow are undertaken. Instead of conducting these trials on plantsand animals grown anyhow, the experimental material will be plants andanimals, properly selected, efficiently managed, and nourished by or onthe produce of a fertile soil. Such plants can be sprayed with activefungous and insect material without harm. Among such herds of cattle,cases of foot-and-mouth disease can be introduced without any danger ofserious infection. The afflicted animals themselves will recover. Whensome audacious innovator of the Hosier type, who has no interest in themaintenance of the existing research structure, conducts suchexperiments, the vast fabric of disease-control which has been erectedin countries like Great Britain will finally collapse. Farmers willemancipate themselves from the thralldom created by the fear of theparasite. Another step forward will be taken which will not stop atfarming.
My self-imposed task is approaching completion. I have examined in greatdetail for forty years the principles underlying the treatment of plantand animal diseases, as well as the practice based on these principles.It now remains to sum up this experience and to offer suggestions forthe future.
There can be no doubt that the work in progress on disease at theExperiment Stations is a gigantic and expensive failure, that itscontinuance on present lines can lead us nowhere and that steps must betaken without delay to place it on sounder lines.
The cause of this failure is not far to seek. The investigations havebeen undertaken by specialists. The problems of disease have not beenstudied as a whole, but have been divorced from practice, split up,departmentalized and confined to the experts most conversant with theparticular fragment of science which deals with some organism associatedwith the disease.
This specialist approach is bound to fail. This is obvious when weconsider: (1) the real problem--how to grow healthy crops and how toraise healthy animals, and (2) the nature of disease--the breakdown ofa complex biological system, which includes the soil in its relation tothe plant and the animal. The problem must include agriculture as anart. The investigator must therefore be a farmer as well as a scientist,and must keep simultaneously in mind all the factors involved. Above allhe must be on his guard to avoid wasting his life in the study of amare's nest: in dealing with a subject which owes its existence to badfarming which will disappear the moment sound methods of husbandry areemployed.
The problems presented by the retreat of the crop and of the animalbefore the parasite and the conventional methods of investigation ofthese questions are clearly out of relation. It follows therefore that aresearch organization which has lost direction and has permitted such astate of things to arise and to develop must itself be in need ofoverhaul. This task has been attempted; the existing structure ofagricultural research has been subjected to a critical examination; theresults are set out in Chapter XIII.
HOWARD, A. Crop Production in India, Oxford University Press,1924, p. 176.
-------'The Role of Insects and Fungi in Agriculture', Empire CottonGrowing Review, xiii, 1936, p. 186.
-------'Insects and Fungi in Agriculture', Empire Cotton Growing Review,xv, 1938, p. 215.
TIMSON, S. D. 'Humus and Witchweed', Rhodesia Agricultural Journal,xxxv, 1938, p. 805.
SOIL FERTILITY AND NATIONAL HEALTH
In the last chapter the retreat of the crop and the animal before theparasite was discussed. Disease was regarded as Nature's verdict onsystems of agriculture in which the soil is deprived of its manurialrights. When the store of humus is used up and not replenished, bothcrops and animals first cease to thrive and then often fall a prey todisease. In other words, one of the chief causes of disease on the farmis bad soil management.
How does the produce of an impoverished soil affect the men and womenwho have to consume it? This is the theme of the present chapter. It isdiscussed, not on the basis of complete results, but from the point ofview of a very promising hypothesis for future work. No otherpresentation is possible because of the paucity, for the moment, ofdirect evidence and the natural difficulties of the subject.
In the case of crops and live stock, experiments are easy. Theinvestigator is not hampered in any way; he has full control of hismaterial and freedom in experimentation. He cannot experiment on humanbeings in the same way. The only subjects that might conceivably be usedfor nutrition experiments on conventional lines are to be found inconcentration camps, in convict prisons, and in asylums. Objections tousing them for such purposes would almost certainly be raised. Even ifthey were not, the investigator would be dealing with life in captivityand with abnormal conditions. Any results obtained would not necessarilyapply to the population as a whole.
Perhaps the chief difficulty at the moment in following up the possibleconnexion between the produce of a fertile soil and the health of thepeople who have to consume it, is to obtain from well-farmed landregular supplies of such produce in a perfectly fresh condition. Exceptin a few cases, food is not marketed according to the way it is grown.The buyer knows nothing of how it was manured. The only way to obtainsuitable material would be for the investigator to take up a piece ofland and grow the food itself. This, so far as my knowledge goes, hasnot been done. This omission explains the scarcity of direct results andwhy so little real progress has been made in human nutrition. Most ofthe work of the past has been founded on the use of food material veryindifferently grown. Moreover, no particular care has been taken to seethat the food has been eaten fresh from its source. Such investigationstherefore can have no solid foundation.
Apart from the evidence that can be gathered from nutrition experiments,is there anything to be learnt about health from agriculture itself? Canthe East which, long before the Roman Empire began or America wasdiscovered, had already developed the systems of good farming which arein full swing to-day, throw any light on the relation between a fertilesoil and a healthy population? It is well known that both China andIndia can show large areas of well-farmed land, which for centuries havecarried very large populations. Unfortunately two factors--overpopulationand periodic crop failures due to irregular rainfall--make it almostimpossible to draw any general lessons from these countries. Thepopulation, looked at in the mass, is always recovering from onecatastrophe after another. Over-population introduces a disturbingfactor--long-continued semi-starvation--so powerful in its effectson the race and on the individual that any benefits arising from afertile soil are entirely obscured.
When, however, the population of the various parts of India is examined,very suggestive differences between the races which make up its 350million inhabitants are disclosed. The physique seen in the northernarea is strikingly superior to that of the southern, eastern, andwestern tracts. We owe the investigation of the causes of thesedifferences to McCarrison, who found that they corresponded with thefood consumed. There is a gradually diminishing value in the food fromthe north to the east, south and west in respect of the amount andquality of the proteins, the quality of the cereal grains forming thestaple article of diet, the quantity and quality of the fats, themineral and vitamin content, as well as in the balance of the food as awhole.
Generally speaking the people of northern India, which include some ofthe finest races of mankind, are wheat eaters, the wheat being consumedin the form of thin, flat cakes made from flour, coarse but fresh-groundin a quern. All the proteins, vitamins, and mineral salts in the grainare consumed. The second most important article of diet is fresh milkand milk products--clarified butter, curds, and buttermilk; the thirditem is the seed of pulse crops; the fourth vegetables and fruit. Meat,as a rule, is very sparingly eaten except by the Pathans.
Turn now to the other parts of India, east, west, and south, in whichthe rice tracts provide the staple food. This cereal--a relatively poorgrain at best--is parboiled, milled or polished, washed in many changesof water, and finally boiled. It is thereby deprived of much of itsprotein and mineral salts and of almost all its vitamins. In addition,very little milk or milk products are consumed, while the proteincontent of the diet is low both in amount and quality. Vegetables andfruit are only sparingly eaten. It is these shortcomings in their foodthat explain the poor physique of the peoples of the rice areas.
In order to prove that these bodily differences were due to food,McCarrison carried out experiments on young growing rats. When younggrowing rats of healthy stock were fed on diets similar to those of theraces of northern India, the health and physique of the rats were good;when they were fed on the diets in vogue in the rice areas, the healthand physique of the rats were bad; when they were fed on the diets ofraces with middling physique, the health and physique of the rats weremiddling. Other things being equal, good or bad diet led to good or badhealth and physique.
When the health and physique of the various northern Indian races werestudied in detail the best were those of the Hunzas, a hardy, agile, andvigorous people, living in one of the high mountain valleys of theGilgit Agency, where an ancient system of irrigated terraces has beenmaintained for thousands of years in a high state of fertility. There islittle or no difference between the kinds of food eaten by these hillmenand by the rest of northern India. There is, however, a great differencein the way these foods are grown. The total area of the irrigatedterraces of the Hunzas is small; ample soil aeration results from theirconstruction; the irrigation water brings annual additions of fine siltproduced by the neighbouring glacier; the very greatest care is taken toreturn to the soil ail human, animal, and vegetable wastes after beingfirst composted together. Land is limited: upon the way it is lookedafter life depends. A perfect agriculture, in which all the factors thatcombine to produce high quality in food, naturally results.
What of the people who live upon this produce? In The WHEEL OF HEALTH,Wrench has gathered together all the information available and has laidstress on their marvellous agility and endurance, good temper andcheerfulness. These men think nothing of covering the 60 miles to Gilgiton foot in one stretch, doing their business and then returning.
There is one point about the Hunza agriculture which needs furtherinvestigation. The staircase cultivation of these hillmen receivesannual dressings of fresh rock-powder, produced by the grinding effectof the glacier ice on the rocks and carried to the fields in theirrigation water. Is there any benefit conferred on the soil and on theplant by these annual additions of finely divided materials? We do notknow the composition of this silt. If it contains finely dividedlimestone its value is obvious. If it is made up for the most part ofcrushed silicates, its possible significance awaits investigation. Dothe mineral residues in the soil need renewal as humus does? If so, thenNature has provided us with an Experiment Station ready-made and withresults that cannot be neglected. Perhaps in the years to come, someheaven-sent investigator of the Charles Darwin type will go thoroughlyinto this Hunza question on the spot, and will set out clearly all thefactors on which their agriculture and their marvellous health depend.
A study of the races of India and of their diet, coupled with theexperimental work on rats carried out by McCarrison, leaves no doubtthat the greatest single factor in the production of good health is theright kind of food and the greatest single factor in the production ofbad health is the wrong kind of food. Further, the very remarkablehealth and physique enjoyed by the Hunza hillmen appears to be due tothe efficiency of their ancient system of farming.
These results suggest that the population of Great Britain should bestudied and the efficiency of our food supply investigated. If thephysique and health of a nation ultimately depend on the fresh produceof well-farmed land, if bad farming is a factor in the production ofpoor physique and bad health, we must set about improving ouragriculture without delay.
Two very different methods have recently been employed for testing theefficiency of the food supply of this country. In the first case(Cheshire) the population of a whole county, which includes both ruraland urban areas, has been studied in the mass for a period oftwenty-five years and the general results have been recorded. In thesecond case (Peckham) a number of families have been periodicallyexamined with a view to throwing light on the general health andefficiency of a group of comparatively well-to-do workers in a city likeLondon.
The methods adopted in the study of the population of Cheshire and inthe publication of the results are highly original. About twenty-fiveyears ago, the National Health Insurance Act for the Prevention and Cureof Sickness came into force. This measure has brought the populationunder close medical observation for a quarter of a century. If theexperience of the Panel and family doctors of the county could besynthesized, valuable information as to the general health of thecommunity would be available. This has been accomplished. The localMedical and Panel Committee of Cheshire, which is in touch with the 600family doctors of the county, has recorded its experience in the form ofa Medical Testament. They find it possible to report definite progressin the 'Cure of Sickness'--the second part of the objective framed bythe National Health Insurance Act. There is no doubt that we have learntto 'postpone the event of death' and this is the more remarkable in viewof the rise in sickness, in short the failure of the first part of theAct's objective. On this latter count there is no room for complacency.
'Our daily work brings us repeatedly to the same point--this illnessresults from a life-time of wrong nutrition.' They then examine theconsequences of wrong nutrition under four heads--bad teeth, rickets,anaemia, and constipation--and indicate how all this and much othertrouble can be prevented by right feeding. For example, in dealing withthe bad teeth of English children some striking facts are emphasized. In1936 out of 3,463,948 schoolchildren examined, no less than 2,425,299needed dental treatment. That this reproach can be removed has beenshown by Tristan da Cunha, where the population is fed on the freshproduce of sea and soil--fish, potatoes, and seabirds' eggs are thestaple diet with sufficient milk and butter, meat occasionally and somevegetables--all raised naturally without the help of artificial manuresand poison sprays. In 1932, 156 persons examined had 3,181 permanentteeth of which 74 were carious. Imported flour and sugar have beenbrought in to a greater extent of late, which may account for thetendency of the teeth to deteriorate observed in 1937.
The Testament then goes on to the work of McCarrison (referred to above)'whose experiments afford convincing proof of the effects of food andguidance in the application of the knowledge acquired'. This has beenapplied in local practice in Cheshire and the results have been amazing.Two examples will suffice.
1. In a Cheshire village the nutrition of expectant mothers issupervised by the local doctor once a month. The food of the mother iswhole-meal bread, raw milk, butter, Cheshire cheese, oatmeal porridge,eggs, broth, salads in abundance, green leaf vegetables, liver and fishweekly, fruit in abundance and a little meat. The whole-meal bread ismade from a mixture of two parts locally grown wheat, pulverized by asteel fan revolving 2,500 times a minute, and one part of raw wheat-germ(fresh off the rollers of a Liverpool mill). The flour is baked withinthirty-six hours at most--a point to be rigidly insisted upon--and arather close but very palatable bread is obtained. With rare exceptionsthe mothers feed their infants at the breast--nine months is advised andthen very slow weaning finishing at about a year. The nursing mother'sfood continues as in pregnancy; the infants are fed five times a daywith four-hour intervals beginning at 6 a.m. The children are splendid;perfect sets of teeth are now more common; they sleep well; pulmonarydiseases are almost unknown; one of their most striking features istheir good humour and happiness. They are sturdy-limbed, beautifullyskinned, normal children. This was not a scientific experiment. It waspart of the work of family practice. The human material was entirelyunselected and the food was not specially grown; but that, in spite ofthese imperfections, the practical application of McCarrison's workshould yield recognizable results shows that in a single generationimprovement of the race can be achieved.
2. A young Irishman aged 23, with a physique and an alertness of mindand body it was a delight to behold, was found to be suffering fromcatarrhal jaundice after two months' residence in England, where he hadbeen living on a diet mostly composed of bacon, white bread, meatsandwiches and tea, with a little meat and an occasional egg. In Irelandhis food had consisted of the fresh natural products of thesoil--potatoes, porridge, milk and milk products, broth (made fromvegetables) and occasional meat, eggs, and fish. The change over to adiet of white bread and sophisticated food was at once followed bydisease. This case shows how quickly good health can be lost by improperfeeding.
The Testament then leaves the purely medical domain and deals with thatprinciple or quality in the varied diets which produces the sameresult--health and freedom from disease (such as the Esqulmaux on flesh,liver, blubber, and fish; the Hunzas and Sikhs on wheaten chappattis,fruit, milk, sprouted legumes and a little meat; the islanders ofTristan on potatoes, seabirds' eggs, fish, and cabbage). In all thesecases the diets have one thing in common--the food is fresh and littlealtered by preparation. The harvest of the sea is a natural product.When the foods are based on agriculture, the natural cycle from soil toplant, animal and man is complete without the intervention of anychemical or substitution phase. In other words, when the natural produceof sea and soil has escaped the attention of agricultural science andthe various food preservation processes, it would seem that healthresults and that there is a marked absence of disease.
The last part of the Medical Testament deals with my own work on theconnexion between a fertile soil and healthy plants and animals; withthe means by which soil fertility can be restored and maintained; with anumber of examples in which this has been done. These have already beendescribed and need not be repeated.
This remarkable document concludes with the following words:
'The better manuring of the home land so as to bring an ample successionof fresh food crops to the tables of our people, the arrest of thepresent exhaustion of the soil and the restoration and permanentmaintenance of its fertility concern us very closely. For nutrition andthe quality of food are the paramount factors in fitness. No healthcampaign can succeed unless the materials of which the bodies are builtare sound. At present they are not.
'Probably hall our work is wasted' since our patients are so fed fromthe cradle, indeed before the cradle, that they are certaincontributions to a C3 nation. Even our country people share the whitebread, tinned salmon, dried milk regime. Against this the efforts of thedoctor resemble those of Sisiphus.
'This is our medical testament, given to all whom may concern--and whomdoes it not concern?'
The Testament was put to a public meeting held at Crewe on March 22nd,1939, by the Lord Lieutenant of Cheshire, Sir WilliamBromley-Davenport, and carried by a unanimous vote. More than fivehundred persons representing the activities of the County of Cheshirewere present. The Medical Testament was published in full in the issueof the British Medical Journal of April 15th, 1939. It has been widelynoticed in the press all over the Empire.
The experience of the Cheshire doctors is supported by the work ofDoctors Williamson and Pearse at the Peckham Health Centre in SouthLondon. In connexion with the study of families whose average wage isbetween 3 pounds 15s. and 4 pounds 10s. a week, about 20,000 medicalexaminations have been recorded. The results have recently been publishedin book form under the title BIOLOGISTS IN SEARCH OF MATERIAL(Faber & Faber). It was found that no less than 83 per cent. of apparentlynormal people had something the matter with them, ranging from some minormaladjustment to incipient disease. One of the most importantcontributions of these Peckham pioneers has been to unearth thebeginnings of a C3 population. The next step will be to see how farthese early symptoms of trouble can be removed by fresh food grown onfertile soil. For this the Centre must have: (1) a large area of land ofits own on which vegetables, milk, and meat can be raised, and (2) amill and bakehouse in which whole-meal bread, produced on Cheshire linesfrom English wheat grown on fertile soil, can be prepared. In this way alarge amount of food resembling that of the Hunza hillmen can beobtained. The medical records of the families which consume thisproduce, after the change over from the canned stuffof the shops and thesemi-carrion of the cold stores has been made, will form interestingreading.
The health of our population has been studied by these two verydifferent methods. Both lead to the same conclusion, namely, that all isnot well: that there is an enormous amount of indisposition,inefficiency, and actual disease. The Medical Testament boldly suggeststhat want of freshness in the food and improper methods of agricultureare at the root of the mischief. This provides a stimulating hypothesisfor future work. A case for action has been established. The basis ofthe public health system of the future has been foreshadowed.
A certain amount of supporting evidence is already available. Two recentexamples can be quoted, the first dealing with live stock, the secondwith schoolboys.
At Marden Park in Surrey, Sir Bernard Greenwell has found that a changeover to a ration of fresh home-grown food (raised on soil manured withhumus) fed to poultry and pigs has been followed by three importantresults: (1) the infantile mortality has to all intents and purposesdisappeared; (2) the general health and well-being of the live stock hasmarkedly improved; (3) a reduction of about lo per cent. in the rationhas been obtained because such home-grown produce possesses anextra-satisfying power.
At a large preparatory school near London, at which both boarders andday-boys are educated, the change over from vegetables, grown withartificial manures, to produce grown on the same land with Indorecompost has been accompanied by results of considerable interest toparents and to the medical profession. Formerly, in the days whenartificials were used, cases of colds, measles, and scarlet fever usedto run through the school. Now they tend to be confined to the singlecase imported from outside. Further, the taste and quality of thevegetables have definitely improved since they were raised with humus.
Much more work on these lines is needed. A search will have to be madethroughout Great Britain and Northern Ireland for resident communitiessuch as boarding-schools, training centres, the resident staff ofhospitals and convalescent homes which satisfy the following fourconditions: (1) the control of sufficient fertile and well-farmed landfor growing the vegetables, fruit, milk and milk products, and meatrequired by the residents; (2) a mill and bakehouse for producingwholemeal bread with the new Cambridge wheats grown on fertile soilwithout the assistance of artificial manures; (3) the medicalsupervision of the community by a carefully chosen disciple ofpreventive medicine; (4) a man or woman in control who is keenlyinterested in putting the findings of the Medical Testament to the testand who is prepared to surmount any difficulties that may arise. In avery few years it is more than probable that islands of health willarise in an ocean of indisposition. No controls will be necessary--thesewill be provided by the country-side round about. Elaborate statisticswill be superfluous as the improved health of these communities willspeak for itself and will need no support from numbers, tables, curves,and the higher mathematics. Mother earth in the appearance of herchildren will provide all that is necessary. The materials for MedicalTestament No. 2 will then be available. Cheshire no doubt will againtake the lead and provide a second milestone on the long road which mustbe traversed before this earth can be made ready to receive herchildren.
In this work research can assist. Medical investigations should bedeflected from the sterile desert of disease to the study of health--tomankind in relation to his environment. Agricultural search, afterreorganization on the lines suggested in the next chapter, should startafresh from a new base-line--soil fertility--and so provide the rawmaterial for the nutritional studies of the future--fresh produce fromfertile soil. The agricultural colleges with their farms should devotesome of their resources to feeding themselves, and so demonstrating whatthe products of well-farmed land can accomplish. They should strive toequal and then to surpass what a tribe of northern India has alreadyachieved.
SCOTT WILLIAMSON, G., and INNES PEARSE, H. Biologists in Search ofMaterial, Faber & Faber, London, 1938.
HOWARD, SIR ALBERT. 'Medical Testament on Nutrition', British MedicalJournal, May 27th, 1939, p. 1106.
MCCARRISON, SIR ROBERT. 'Nutrition and National Health' (Cantor Lectures),Journal of the Royal Society of Arts, lxxxiv, 1936, pp. 1047, 1067,and 1087.
-------'Medical Testament on Nutrition', Supplement to the BritishMedical Journal, April 15th, 1939, p. 157; Supplement to the New EnglishWeekly, April 6th, 1939.
WRENCH, G. T. The Wheel of Health, London, 1938.
PART IV AGRICULTURAL RESEARCH
A CRITICISM OF PRESENT-DAY AGRICULTURAL RESEARCH
A want of relation between the conventional methods of investigation andthe nature of disease in plants and animals has been shown to exist. Thevast fabric of agricultural research must now be examined in order todetermine whether effective contact has been maintained with theproblems of farming. This is the theme of the present chapter.
The application of science to agriculture is a comparatively moderndevelopment, which began in 1834 when Boussingault laid the foundationsof agricultural chemistry. Previously all the improvements in farmingpractice resulted from the labours of a few exceptional men, whoseinnovations were afterwards copied by their neighbours. Progress tookplace by imitation. After 1834 the scientific investigator became afactor in discovery. The first notable advance by this new agencyoccurred in 1840, when Liebig's classical monograph on agriculturalchemistry appeared. This at once attracted the attention ofagriculturists. Liebig was a great personality, an investigator ofgenius endowed with imagination, initiative, and leadership and wasexceptionally well qualified for the scientific side of his task--theapplication of chemistry to agriculture. He soon discovered twoimportant things: (1) that the ashes of plants gave useful informationas to the requirements of crops, and (2) that a watery extract of humusgave little or no residue on evaporation. As the carbon of the plant wasobtained from the atmosphere by assimilation in the green leaf,everything seemed to point to the supreme importance of the soil and thesoil solution in the raising of crops. It was only necessary to analysethe ashes of plants, then the soil, and to apply to the latter thenecessary salts to obtain full crops. To establish the new point of viewthe humus theory, which then held the field, had to be demolished.According to this theory the plant fed on humus. Liebig believed he hadshown that this view was untenable; humus was insoluble in water andtherefore could not influence the soil solution.
In all this he followed the science of the moment. In his onslaught onthe humus theory he was so sure of his ground that he did not call inNature to verify his conclusions. It did not occur to him that while thehumus theory, as then expressed, might be wrong, humus itself might beright. Like so many of his disciples in the years to come, he failed toattach importance to the fact that the surface soil always contains veryactive humus, and did not perceive that critical field experiments,designed to find out if chemical manures were sufficient to supply allthe needs of crops, should always be done on the sub-soil, afterremoving the top 9 inches or so. If this is not arranged for, the yieldof any crop may be influenced by the humus already in the soil. Failureto perceive this obvious fact is the main reason why Liebig and hisdisciples went astray.
He also failed to realize the supreme importance to the investigator ofa first-hand knowledge of practical-agriculture, and the significance ofthe past experience of the tillers of the soil. He was only qualifiedfor his task on the scientific side; he was no farmer; as aninvestigator of the ancient art of agriculture he was only half a man.He was unable to visualize his problem from two very different points ofview at one and the same moment--the scientific and the practical. Hisfailure has cast its shadow on much of the scientific investigation ofthe next hundred years. Rothamsted, which started in 1843, wasprofoundly influenced by the Liebig tradition. The celebratedexperiments on Broadbalk Field caught the fancy of the farming world.They were so telling, so systematic, so spectacular that they set thefashion till the end of the last century, when the great era ofagricultural chemistry began to wane. During this period (1840-1900),agricultural science was a branch of chemistry; the use of artificialmanures became firmly welded into the work and outlook of the ExperimentStations; the great importance of nitrogen (N), phosphorus (P), andpotash (K) in the soil solution was established; what may briefly bedescribed as the NPK mentality was born.
The trials of chemical manures, however, brought the investigators fromthe laboratory to the land; they came into frequent contact withpractice; their outlook and experience gradually widened. One result wasthe discovery of the limitations of chemical science; the deficienciesof the soil, suggested by chemical analysis, were not always made up bythe addition of the appropriate artificial manure; the problems of cropproduction could not be dealt with by chemistry alone. The physicaltexture of the soil began to be considered; the pioneering work ofHilgard and King in America led to the development of a new branch ofthe subject--soil physics--which is still being explored. Pasteur's workon fermentation and allied subjects, by drawing attention to the factthat the soil is inhabited by bacteria and other forms of life,disclosed a new world. A notable elucidation of the complex life of thesoil was contributed by Charles Darwin's fascinating account of theearthworm. The organisms concerned with the nitrification of organicmatter were discovered by Winogradsky and the conditions necessary fortheir activity in pure cultures were determined. Another branch ofagricultural science--soil bacteriology--arose. While the biology andphysics of the soil were being studied, a new school of soil sciencearose in Russia. Soils began to be regarded as independent naturalgrowths: to have form and structure due to climate, vegetation, andgeological origin. Systems of soil classification, based primarily onthe soil profile, with an appropriate nomenclature developed in harmonywith these views, which, for the moment, have been widely accepted. Anew branch of soil science--pedology--arose. The Liebig conception ofsoil fertility was thus gradually enlarged and it became clear that theproblem of increasing the produce of the soil did not lie within thedomain of any one science but embraced at least four--chemistry,physics, bacteriology, and geology.
At the beginning of the present century, the investigators began to paymore attention to what is after all the chief agent in cropproduction--the plant itself. The rediscovery of Mendel's law byCorrens, the conception of the unit species which followed the work ofJohannsen and the recognition of its importance in improvement byselection have led directly to the modern studies of cultivated crops,in which the Russians have made such noteworthy contributions. The wholeworld is now being ransacked to provide the plant breeders with a widerange of raw material. These botanical investigations are constantlybroadening and now embrace the root system, its relation to the soiltype, the resistance of the plant to disease, as well as the internalmechanism by which inheritance takes place. The practical results of thelast forty years which have followed the application of botanicalscience to agriculture are very considerable. In wheat, for example, thelabours of Saunders in Canada led to the production of Marquis, an earlyvariety with short straw, which soon covered 20,000,000 acres in Canadaand the neighbouring States of the Union. This is the most successfulwheat-hybrid yet produced. In Australia the new wheats raised by Farrerwere soon widely cultivated. In England the new hybrids raised atCambridge established themselves in the wheat-growing areas of thiscountry. In India the Pusa wheats covered several million acres of land.By 1915 the total area of the new varieties of wheat had reached over25,000,000 acres. When the annual dividend, in the form of increasedwealth, was compared with the capital invested in these investigations,it was at once evident that the return was many times greater than thatyielded by the most successful industrial enterprise. Similar resultshave been obtained with other crops. The new varieties of maltingbarley, raised by Beaven, have for years been a feature of the Englishcountry-side; the new varieties of sugarcane produced by Barber atCoimbatore in South India soon replaced the indigenous types of cane innorthern India. In cotton, jute, rice, grasses, and clovers and manyother crops new varieties have been obtained; the old varieties arebeing systematically replaced. Nevertheless the gain per acre obtainedby changing the variety is as a rule small. As will be seen in the nextchapter, the great problem of agriculture at the moment is the intensivecultivation of these new types; how best to arrange a marriage betweenthe new variety and a fertile soil. Unless this is done, the value of anew variety can only be transient; the increased yield will be obtainedat the expense of the soil capital; the labours of the plant breederswill have provided another boomerang.
A number of other developments have taken place which must briefly bementioned. Since the Great War the factories then engaged in thefixation of atmospheric nitrogen for the manufacture of the vastquantities of explosives, needed to defend and to destroy armies wellentrenched, have had to find a new market This was provided by the largearea of land impoverished by the over-cropping of the war period. Ademand was created by the low price at which the mass-produced unit ofnitrogen could be put on the market and by the reliability of theproduct. Phosphates and potash fell into line Ingenious mixtures ofartificial manures, containing everything supposed to be needed by thevarious crops, could be purchased all over the world. Sales increasedrapidly; the majority of farmers and market gardeners soon based theirmanurial programme on the cheapest forms of nitrogen, phosphorus, andpotash or on the cheapest mixtures. During the last twenty years theprogress of the artificial manure industry has been phenomenal; the ageof the manure bag has arrived; the Liebig tradition returned in fullforce.
The testing of artificial manures and new varieties has necessitatedinnumerable field experiments, the published results of which arebewildering in their volume, their diversity, and often in theconclusions to be drawn from them. By a judicious selection of thismaterial, it is possible to prove or disprove anything or everything.Something was obviously needed to regulate the torrent of field resultsand to ensure a greater measure of reliability. This was attempted bythe help of mathematics. The technique was overhauled; the field plotswere 'replicated' and 'randomized'; the figures were subjected to arigid statistical scrutiny. Only those results which are fortunateenough to secure what has been described as the fastidious approval ofthe higher mathematics are now accepted. There is an obvious weakness inthe technique of these field experiments which must be mentioned. Smallplots and farms are very different things. It is impossible to manage asmall plot as a self-contained unit in the same way as a good farm isconducted. The essential relation between live stock and the land islost; there are no means of maintaining the fertility of the soil bysuitable rotations as is the rule in good farming. The plot and the farmare obviously out of relation; the plot does not even represent thefield in which it occurs. A collection of field plots cannot representthe agricultural problem they set out to investigate. It follows thatany findings based on the behaviour of these small fragments ofartificially manured land are unlikely to apply to agriculture. Whatpossible advantage therefore can be obtained by the application of thehigher mathematics to a technique which is so fundamentally unsound?
With the introduction of artificials there has been a continuousincrease in disease, both in crops and in live stock. This subject hasalready been discussed. It is mentioned again to remind the reader ofthe vast volume of research on this topic completed and in progress.
Side by side with the intrusion of mathematics into agriculture, anotherbranch of the subject has grown up--economics. The need for reducingexpenditure so that farming could yield a profit has brought everyoperation, including manuring and the treatment of disease, underexamination in order to ascertain the cost and what profit, if any,results. Costings are everywhere the rule; the value of any experimentand innovation is largely determined by the amount of profit which canbe wrung from Mother earth. The output of the farm and of the factoryhave been looked at from the same standpoint--dividends. Agriculturejoined the ranks of industry.
Agricultural science, like Topsy, has indeed grown. In little more thanforty years a vast system of research institutes, experimental farms,and district organizations (for bringing the results of research to thefarming community) has been created all over the world. As this researchstructure has grown up in piecemeal fashion as a result of the work ofthe pioneers, it will be interesting to examine it and to ascertainwhether or not direction has been maintained. Has the presentorganization any virtue in itself or does it merely crystallize thestages reached in the scientific exploration of a vast biologicalcomplex? If it is useful it will be justified by results; if its valueis merely historical, its reform can only be a question of time.
In Great Britain two documentas have recently appeared (Constitution andFunctions of the Agricultural Research Council, H.M. Stationery OfficeLondon, 1938; Report on Agricultural Research in Great Britain, PEP., 16Queen Anne's Gate, London, S.W. 1, 1938.) which make it easy to conductan inquest on agricultural research in this country. They describe fullythe structure and working of the offficial machine which controls andfinances research, the organization of the work itself, and the methodsof making the results known to farmers. In addition to the Treasury andthe Committee of the Privy Council, official control is exercised by noless than three other organizations: (1) The Ministry of Agriculture(which administers the grants); (2) the Development Commission (whichawards funds from grants placed at its disposal by the Treasury); and(3) the Agricultural Research Council (which reviews and advises onapplications for grants, and also coordinates State-aided agriculturalresearch in Great Britain). Eventually the Research Institutes, whichcarry out the work, are reached.
These Research Institutes are fifty in number and are of three types:
(a) Government laboratories or research stations;
(b) Institutes attached to universities or university colleges;
(c) Independent institutes.
Most of these institutes were set up in 1911 to provide for basicresearch in each of the agricultural sciences: agricultural economics,soil science, plant physiology, plant breeding, horticulture and fruitresearch, plant pathology, animal heredity and genetics, animalphysiology and nutrition, animal diseases, dairy research, foodpreservation and transport, agricultural engineering and agriculturalmeteorology. These groups can again be divided into four classes:background research (dealing with fundamental scientific principles);basic research (the recognized sphere of the research institute); ad hocresearch (the study of specific practical problems, as they arise, suchas the control of foot-and-mouth disease); pilot or development research(such as the growing on of new strains of plants).
After research proper, the organization then deals with the results ofits investigations. The first stage in this process is the ProvincialAdvisory Service which operates in sixteen provinces. From one to sevenAdvisory Officers are stationed at each centre, their specializedknowledge being at the disposal of County Organizers and farmers. Thefinal link in the long chain from the Treasury to the soil is providedby the Agricultural Organizers of the County Councils, who act as a freeScientific Information Bureau for farmers and market gardeners. Mostcounties also support farm institutes-which provide technical educationand also have experimental farms of their own. Appended to this researchstructure are two Imperial Institutes and nine Imperial Bureaux, whichprovide an information and abstracting service in entomology, mycology,soil science, animal health, animal nutrition and genetics, plantgenetics, fruit production, agricultural parasitology, and dairying. Thenumber of agricultural research workers in Great Britain is about 1,000.The total State expenditure on agricultural research amounted in 1938 toabout 700,000 pounds. This is about 90 per cent. of the total cost, theremaining 10 per cent. being met by local authorities, universities,marketing boards, private companies and individuals, agriculturalsocieties, fees, and sales of produce. The farmers, even when organizedas marketing boards, have shown little recognition of the value ofresearch and make no serious contribution to its cost.
A formidable, complex, and costly organization has thus grown up since1911. No less than seven organs of the Central Government have to dowith agricultural research, the personnel of which has to be fed with aconstant stream of reports, memoranda, and information which must absorba large amount of the time and energy of the men who really matter--theinvestigators. A feature of the official control is the committee, adevice which has developed almost beyond belief since the AgriculturalResearch Council came into being in 1934. Six standing committees werefirst formed to carry out a survey of existing research. These led to acrop of new committees to go farther into matters disclosed by thispreliminary survey. In addition to the six standing committees, no lessthan fifteen scientific committees are dealing with the most importantbranches of research. Twelve of these fifteen committees are consideringthe diseases of crops and live stock--the main preoccupation of theCouncil at the present time.
Is so much machinery necessary? Between the Treasury (which decides whatsum can be granted) and the Research Institutes, would not a singleagency such as the Ministry of Agriculture be all that is needed in theway of control? This would appear likely when it is remembered thatthere is one thing only in research that matters--the man or woman whois to undertake it. Once these are found and provided with the means,nothing else is necessary. The best service the official organizationcan then perform is to remain in the background, ready to help when theworkers need assistance. It follows then that simplicity and modestymust always be the keynote of the controlling authority.
A serious defect in the research organization proper is encountered atthe very beginning. The Research Institutes are organized on the basisof the particular science, not on recognized branches of farming. Theinstrument (science) and the subject (agriculture) at once lose contact.The workers in these institutes confine themselves to some aspect oftheir specialized field; the investigations soon becomedepartmentalized; the steadying influence of firsthand practicalexperience is the exception rather than the rule. The reports of theseResearch Institutes describe the activities of large numbers of workersall busy on the periphery of the subject and all intent on learning moreand more about less and less. Looked at in the mass, the most strikingfeature of these institutions is the fragmentation of the subject intominute units. It is true that attempts are made to co-ordinate thiseffort by such devices as the formation of groups and teams, but as willbe shown later this rarely succeeds. Another disquieting feature is thegap between science and practice. It is true that most, if not all, ofthese establishments possess a farm, but this is mostly taken up withsets of permanent experiments. I know of no research institute in GreatBritain besides Aberystwyth where a scientific worker has under hispersonal control an area of land with his own staff where he can followthe gleam wheresoever it may lead him. Even Aberystwyth stops shortbefore the animal is reached. The improved strains of herbage plants andthe method of growing them are not followed to their logicalconclusion--a flock of healthy sheep ready for the market and a supplyof well-nourished animals by which the breed can be continued.
Has the official machine ever posed to itself such questions as these?What would be the reaction of some Charles Darwin or Louis Pasteur ofthe future to one or other of these institutes? What would have beentheir fate if circumstances had compelled them to remain in such anorganization, working at some fragment of science? How can the excessivedepartmentalization of research provide that freedom without which noprogress has ever been made in science? Is it rational in such a subjectas agriculture to attempt to separate science and practice? Will not theorganization of such research always be a contradiction in terms,because the investigator is born not made? The official reply to thesequestions would form interesting reading.
How does this research organization strike the tillers of the soil forwhose benefit it has been created? The farmers complain that theresearch workers are out of touch with farming needs and conditions;that the results of research are buried in learned periodicals andexpressed in unintelligible language; that these papers deal withfragments of the subject chosen haphazard; that the organization ofresearch. is so cumbersome that the average farmer cannot obtain aprompt answer to an inquiry and that there are no demonstration farms atwhich practical solutions of local problems are to be seen.
There seems to be only one effective answer to these objections. Theexperiment station workers should take their own advice and try outtheir results. The fruits of this research should be forthcoming on theland itself. All the world over this simple method of publication neverfails to secure the respect and attention of the farming community;their response to such messages is always generous and immediate. InGreat Britain, however, the retort of the administration takes anotherline. The idea is fostered that the experiment stations are arsenals ofscientific knowledge which actually needs explanation and dilution forthe farmer and his land to benefit. Thus in dealing with this point thePEP Report states: 'One of the principal tasks of the administrator isto ensure that the general body of scientific knowledge, includingrecent results of the research workers' efforts, is brought to thefarmer in such a way that he can understand it and apply it on hisfarm.' The most effective way of doing this is for the organization todemonstrate, in a practical way for all to see, the value of some, atany rate, of these researches. This simple remedy will silence thecritics and scoffers; any delay in furnishing it will only add fuel tothe fire. After all, a research organization which costs the nation700,000 pounds a year cannot afford to have its operations called inquestion by the very men for whose benefit it has been designed. Thecomplaints of the farming community must be removed.
A system not unlike that just described in Great Britain has beenadopted in the Empire generally. There is, however, one interestingdifference. The official machinery is comparatively simple; themultiplication of agencies and supervisory committees is not sopronounced; the step from the Treasury to the farmer is much shorter.When, however, we come to the research proper, the system is verysimilar to that which obtains in Great Britain. There is the sametendency to divide research into two groups--fundamental and local; torely on the piecing together of fragments of science; to extol theadvantages of co-operation; to adopt the team rather than theindividual. It is the exception rather than the rule to find aninvestigation in the hands of one competent investigator, provided withland, ample means, and complete freedom.
The completion of an imperial chain of experiment stations forfundamental research was emphasized by a Conference (Report of theImperial Agricultural Research Conference, H.M. Stationery Office,London, 1927) which met in London in 1927. The financial depression,which set in soon after the Report appeared, interfered with thisscheme. No additions to the two original links of the chain of five orsix super-Research Institutes contemplated--sometimes irreverentlyreferred to as the 'chain of pearls'--have been added to the one in theWest Indies (Trinidad) and the other in East Africa (Amani).
Two examples will suffice to illustrate the methods now being employedin this fundamental research work. These are taken from a recent paperby Sir Geoffrey Evans, C.I.E., entitled 'Research and Training inTropical Agriculture', which appeared in the Journal of the RoyalSociety of Arts of February 10th, 1939. Sir Geoffrey selected thecurrent work on cacao and bananas when explaining how research isconducted at the Imperial College of Tropical Agriculture in Trinidad.He laid great stress on the merits of team work, a method ofinvestigation which we must now examine. These Trinidad examples ofresearch do not stand alone. They resemble what is going on all over theEmpire, including India. Similar work can be collected by the basketful.
In 1930 a study of cacao was commenced in Trinidad in twodirections--botanical and chemical. After a preliminary examination ofthe crop, which is made up of a bewildering number of types, varyingwidely in fruitfulness and quality, a hundred special trees wereselected as a basis for improvement. As cacao does not breed true fromseed, methods of vegetative reproduction by means of cuttings and budwood were first studied. The mechanism of pollination, however, showedthat cacao is frequently self-sterile and that many of the special treesrequired to be cross-pollinated before they could set seed. Suitablepollen parents had then to be found. Manurial experiments onconventional lines led to numerous field experiments all over the islandas well as to a detailed soil survey. The biochemical study of the cacaobean produced results described as intricate and baffling; nocorrelation between the tannin content and quality emerged. TheEconomics Department of the College investigated the decline of theindustry since the War, and established the interesting fact that acacao plantation reaches its peak in about twenty-five years and thenbegins to decline. The causes of this decline have been studied and thesystem of regenerating old plantations by supplying vacancies withhigh-yielding types has been devised. As, however, the decline of thesecacao estates is more likely to be due to wornout soil than anythingelse, this method by itself is not likely to succeed. Pests and diseasestake their toll of cacao, so the entomologists and mycologists werecalled in to deal with thrips--the most serious insect pest--and thewitch-broom disease--a fungous pest which has done great damage in theWest Indies.
The Trinidad investigations on the banana owe their origin to theoutbreak of the Panama disease (Fusarium cubense) all over the WestIndies and the Central American Republics. When the nature of thetrouble was established by the mycologists, a search for immune andresistant varieties followed. This included plant breeding, theinvestigation of the causes of seedlessness, the raising of numerousseedlings, and the search for the ideal parent from which to breed a newcommercial banana which is disease-resistant, seedless, of good quality,and capable of standing up to transport conditions. In this work theassistance Or the Royal Botanic Gardens at Kew was enlisted; it involvedthe problem of protecting the banana in the West Indies from disease,including virus, when importing from Malaya (the home of the chiefbanana of commerce--the Gros Michel) and other places the materialneeded for the plant-breeding work. The problems of ripening duringtransport, including a study of the respiration processes during gasstorage and the effect of humidity, and the reason for chilling alsoreceived attention.
These interesting investigations, which have as their aim the productionof higher yields of better cacao and better bananas, have been carriedon by what is known as team work. They have necessitated the services ofbotanists, chemists, mycologists, entomologists and economists, and bothhave involved considerable expense and much time.
As examples of the way in which the more difficult problems of tropicalagriculture are now approached by a number of workers, they are typicalof the methods of research everywhere. Many aspects of the cacao andbanana problems have been studied; the methods of research have beenclearly set out. The workers have evidently spared no pains to achievesuccess. Nevertheless, the results are negative. The paper under reviewsuggests that matters are still very much in the programme stage; few ifany tangible results have been obtained; neither the cacao nor thebanana industry has been set on its feet.
If we take a wide view of these two problems and consider: (1) thepresent methods by which cacao and bananas are grown in the West Indies;(2) the indications furnished by disease that all is not well with theseplantations, and (3) the best examples of cacao and banana cultivationto be found in the East where, by means of farm-yard manure only, heavycrops of fine, healthy produce are obtained, the suspicion grows that atleast some vital factors have been forgotten in these Trnidadinvestigations. The spectacular response of cacao trees to humus seemsto have been missed altogether and no attention has been given to thesignificance of the mycorrhizal association in the roots of both cacaotrees and bananas. In the cacao and banana plantations in the WestIndies, there is a want of balance between the crop and the animal.There is insufficient live stock. There is a disquieting amount ofdisease and general unthriftiness, which is associated with the absenceof conditions suitable for mycorrhizal formation.
Practical experience of the best banana and cacao cultivation in Indiaand Ceylon proves beyond all doubt that the two factors which areessential, if satisfactory yields of high quality are to be obtained andthe plantations are to be kept healthy, are: (1) good soil aeration, and(2) supplies of freshly prepared humus from animal and vegetable wastes,which are needed to maintain in effective operation the mycorrhizalassociation. Want of attention to either of these factors is at oncefollowed by loss of quality, by diminished returns, and finally bydisease. A better way of dealing with these West Indian problems wouldhave been by good farming methods, including a proper balance betweencrops and live stock, and by the conversion of all available vegetableand animal wastes into humus.
The Trinidad investigations are quoted as 'an example which can hardlyfail to impress the student investigator with the necessity forco-operation'. In reality all they show is how employment can be foundfor a number of specialists for quite a long time, and indeed what a lotof scientific work can be done by competent workers with purely negativeresults as far as the yield and the quality of the crop are concerned.
It is not difficult to see the weakness of this method of approach. Theproblem is never envisaged as a whole and studied in the field fromevery angle before research on some branch of science is undertaken.Methods of crop improvement are now expected to come from the laboratoryand not from the field as they have always done throughout farminghistory. The control of the team is of necessity very loose. It isnormally placed in the hands of persons of administrative rather thanpractical experience and of limited training in research methods. Oftenthey have other important duties and cannot give the time and thoughtrequired. Unable themselves to make a correct diagnosis of the case inthe field, their only resource is to go on adding specialist afterspecialist to their staff in the hope that the study of a fresh fragmentof the subject will lead them to some solution. It is almost certainthat had the West Indian problems been tackled by one investigator witha real knowledge of farming combined with a wide training in science,and had he been provided with the necessary land, money, and facilitiesand with complete freedom in conducting the investigation, Sir GeoffreyEvans would have told a very different story. From the point of view ofthe students at the Trinidad College, it would have been still better tohave used these crops for illustrating both methods simultaneously--thebanana studied by a single investigator, adequately equipped; cacao bymeans of a team. In this way the relative merits of the two methodscould have been settled for all time. In all probability, two resultswould have been obtained: (1) the principle that the researcher is theonly thing that matters in research would have been established; (2)team work would have ceased to be considered as an effective instrumentof investigation.
Team work offers no solution for the evils which result fromfragmentation of a research problem. The net woven by the team is oftenfull of holes. Is the fragmentation of the problem accompanied by anyother disadvantages? This question is at once answered if we examine anyof the major problems of presentday farming. Two British examples willsuffice to prove that an inevitable consequence of fragmentation andspecialization is loss of direction. Science then loses itself in a mazeof detail.
The retreat of the potato crop before blight, eelworm, and virus is oneof the most disquieting incidents in British agriculture. One of ourmost important food crops cannot now be grown successfully on a fieldscale without a thin film of copper salts; a new rotation of crops fromwhich the potato is omitted until the cysts of the eelworm disappearfrom the soil; a frequent change of seed from Scotland, Wales, orNorthern Ireland. Evidently something is very wrong somewhere, becausethis crop, when grown in thousands of fertile kitchen gardens throughoutthe country, is healthy, not diseased. Agricultural science began byfragmenting this potato problem into a number of parts. Potato blightfell within the province of the mycologist; a group of investigatorsdealt with eelworm; a special experiment station was created for virusdisease; the breeding and testing of disease resistant varieties wasagain a separate branch of the work; the manuring and general agronomyof the crop fell within the province of the agriculturist. Themultiplication of workers obscures rather than clarifies this widebiological problem. The fact that these potato diseases exist at allimplies that some failure in soil management has occurred. The obviousmethod of dealing with a collapse of this kind should have been toascertain the causes of failure rather than to tinker with theconsequences of some mistake in management. The net result has been thatall this work on the periphery of the subject has not solved the problemof how to grow a healthy potato. This is because direction has beencompletely lost.
The same story is repeated in manuring: fragmentation has again beenfollowed by loss of direction. Notwithstanding the fact that in theforest Nature has provided examples to copy and in the peat-bog examplesto avoid, when devising any rational system of manuring, agriculturalscience at once proceeded to fragment the subject. For nearly a hundredyears some of the ablest workers have devoted themselves to a study ofsoil nutrients, including trace elements like boron, iron, and cobalt.Green-manuring is a separate subject, so is the preparation ofartificial farm-yard manure and the study of the ordinary manure heap.The weight of produce and the cost of manuring overshadow questions ofquality. The two subjects which really matter in manuring--thepreservation of soil fertility and the quality of the produce--escapeattention altogether, mainly because direction has been so largely lost.
The insistence on quantitative results is another of the weaknesses inscientific investigation. It has profoundly influenced agriculturalresearch. In chemistry and physics, for example, accurate records areeverything: these subjects lend themselves to exact determinations whichcan be recorded numerically. But the growing of crops and the raising oflive stock belong to biology, a domain where everything is alive andwhich is poles asunder from chemistry and physics. Many of the thingsthat matter on the land, such as soil fertility, tilth, soil management,the quality of produce, the bloom and health of animals, the generalmanagement of live stock, the working relations between master and man,the esprit de corps of the farm as a whole, cannot be weighed ormeasured. Nevertheless their presence is everything: their absencespells failure. Why, therefore, in a subject like this should there beso much insistence on weights and measures and on the statisticalinterpretation of figures? Are not the means (quantitative results andstatistical methods) and the subject investigated (the growth of a cropor the raising of live stock) entirely out of relation the one to theother? Can the operations of agriculture ever be carried out, even on anexperiment station, so that the investigator is sure that everythingpossible has been done for the crop and for the animal? Can a mutuallyinteracting system, like the crop and the soil, for example, dependenton a multitude of factors which are changing from week to week and yearto year, ever be made to yield quantitative results which correspondwith the precision of mathematics?
The invasion of economics into agricultural research naturally followedthe use of quantitative methods. It was an imitation of the successfulapplication of coatings to the operations of the factory and the generalstore. In a factory making nails, for example, it is possible, indeedeminently desirable, to compare the cost of the raw material and theoperations of manufacture, including labour, fuel, overhead expenses,wear and tear and so forth, with the output, and to ascertain how andwhere savings in cost and general speeding up can be achieved. Rawmaterials, output, and stocks can all be accurately determined. In avery short time a manufacturer with brains and energy will know the costof every step in the process to the fourth place of decimals. This isbecause everything is computable. In a similar manner the operations ofthe general store can be reduced to figures and squared paper. The menin the counting-house can follow the least falling-off in efficiency andin the winning of profit. How very natural it was some thirty years agoto apply these principles to Mother earth and to the farmer! The resulthas been a deluge of coatings and of agricultural economics largelybased on guess-work, because the machinery of the soil will alwaysremain a closed book. Mother earth does not keep a pass-book. Almostevery operation in agriculture adds or subtracts an unknown quantity toor from the capital of the soil--fertility--another unknown quantity.Any experimental result such as a crop is almost certain to be partlydue to the transfer of some of the soil's capital to the profit and lossaccount of the farmer. The economics of such operations must thereforebe based on the purest of guess-work. The results can hardly be worththe paper they are written on. The only things that matter on a farm arethese: the credit of the farmer--that is to say what other people,including his labour force and his bank manager, think of him; the totalannual expenditure; the total annual income and the annualvaluation--the condition of the land and of the live and dead stock atthe end of the year. If all these things are satisfactory nothing elsematters. If they are not, no amount of coatings will avail. Why,therefore, trouble about anything beyond these essentials?
But economics has done a much greater disservice to agriculture than thecollection of useless data. Farming has come to be looked at as if itwere a factory. Agriculture is regarded as a commercial enterprise; fartoo much emphasis has been laid on profit. But the purpose ofagriculture is quite different from that of a factory. It has to providefood in order that the race may flourish and persist. The best resultsare obtained if the food is fresh and the soil is fertile. Quality ismore important than weight of produce. Farming is therefore a vitalmatter for the population and ranks with the supply of drinking water,fresh air, and protection from the weather. Our water supplies do notalways pay their way; the provision of green belts and open spaces doesnot yield a profit; our housing schemes are frequently uneconomic. Why,then, should the quality of the food on which still more depends thanwater, oxygen, or warmth be looked at in a different way? The peoplemust be fed whatever happens. Why not, then, make a supreme effort tosee that they are properly fed? Why neglect the very foundation-stone ofour efficiency as a nation? The nation's food in the nature of thingsmust always take the first place. The financial system, after all, isbut a secondary matter. Economics therefore, in failing to insist onthese elementary truths, has been guilty of a grave error of judgement.
In allowing science to be used to wring the last ounce from the soil bynew varieties of crops, cheaper and more stimulating manures, deeper andmore thorough cultivating machines, hens which lay themselves to death,and cows which perish in an ocean of milk, something more than a want ofjudgement on the part of the organization is involved. Agriculturalresearch has been misused to make the farmer, not a better producer offood, but a more expert bandit. He has been taught how to profiteer atthe expense of posterity--how to transfer capital in the shape of soilfertility and the reserves of his live stock to his profit and lossaccount. In business such practices end in bankruptcy; in agriculturalresearch they lead to temporary success. All goes well as long as thesoil can be made to yield a crop. But soil fertility does not last forever; eventually the land is worn out; real farming dies.
In the following chapter an example of the type of research needed inthe future will be described.
CARREL, ALEXIS. Man, the Unknown, London, 1939.
Constitution and Functions of the Agricultural Research Council, H.M.Stationery Office, London, 1938.
DAMPER, SIR WILLIAM C. 'Agricultural Research and the Work of theAgricultural Research Council', Journal of the Farmers' Club, 1938, p. 55.
EVANS, SIR GEOFFREY. 'Research and Training in Tropical Agriculture',Journal of the Royal Society of Arts, lxxxvii, 1939, p. 332.
LIEBIG, J. Chemistry in its Applications to Agriculture and Physiology,London, 1840.
Report of the Imperial Agricultural Research Conference, H.M. StationeryOffice, London, 1927.
Report on Agricultural Research in Great Britain, PEP, 16 OueenAnne's Gate, London, 1938.
A SUCCESSFUL EXAMPLE OF AGRICULTURAL RESEARCH
In the last chapter the agricultural research of to-day was severelycriticized; its many shortcomings were frankly set out; suggestions weremade for its gradual amendment. That these strictures are justified willbe evident if we examine in detail a piece of successful researchcarried out on the sugar-cane crop in India during a period of nearlytwenty-seven years: 1908-35.
In 1910 the investigations on sugar-cane in Northern India were mainlyconcentrated in the United Provinces, where a considerable localindustry was already in existence. Narrow-leaved, thin canes wereplanted under irrigation at the beginning of the hot season in March;the crop was crushed by bullock power during the cold weather (Januaryto March); the juice was converted into crude sugar in open pans. Theyield was low, a little over one ton to the acre on the average. It wasdecided to develop this primitive industry and the work, at first purelychemical, was placed in the hands of Mr. George Clarke, the AgriculturalChemist. The choice proved to be a happy one. Clarke combined afirst-class knowledge of chemistry and general science with considerableexperience of research methods, obtained under Professors Kipping andPope at Nottingham University College and the School of Technology,Manchester. The son of a south Lincolnshire farmer, he had all his lifebeen familiar with good agricultural practice and had inherited a markedaptitude for farming from a long line of yeomen ancestors. He hadtherefore acquired the three preliminary qualifications essential for aninvestigator in agriculture, namely, the makings of a good farmer, asound training in science, and a first-hand acquaintance with methods ofresearch. It will be seen from what follows that he also possessed thegift of correct diagnosis, the capacity to pose to himself the problemsto be investigated, the persistence to solve them, and the drive neededto get the results taken up by the people and firmly welded into thepractice of the country-side.
Clarke was most fortunate in the choice of his staff. He had associatedwith him throughout two Indian officers--S. C. Banerji (afterwards RaiBahadur) and Sheikh Mahomed Naib Husain (afterwards Khan Bahadur).Banerji, who possessed the dignity and repose of his race, was in chargeof the laboratories--always a model of order and efficiency--and wasaccurate and painstaking almost beyond belief. Naib Husain was of a verydifferent temperament--hot-tempered and full of the energy and driveneeded to break new ground in crop production. His absorbing interest inlife was the Shahjahanpur farm and the condition of his crops and henever spared himself to make all he undertook a success. Both these mengave their lives to their work and both lived to see their effortscrowned with success, and the Shahjahanpur farm the centre of perhapsthe most remarkable example of rural development so far achieved. NoEuropean officer in India has ever had more loyal assistants; Indianagriculture has never been served with more devotion. I saw much oftheir work and watched the growth of the modest but efficientorganization they helped to build. It is a great regret to me that theyare not here to read this genuine tribute of admiration and respect froma fellow worker of another race.
It had been the custom till 1912 in the United Provinces to keep theirscientific officers isolated from the practical side of agriculturalimprovement, and there were no clear ideas how the combined scientificand practical problems connected with cane cultivation should betackled. It did not strike any one that it would be necessary for thescientific investigator to grow the crop and master the localagriculture before any improvement could be devised and tried. Whentherefore in 1911 Clarke asked to be provided with a farm, there was agood deal of discussion and some amazement. The matter was referred tothe All-India Board of Agriculture in 1911, where the proposal wasseverely criticized. The agricultural members did not like the idea ofscientific men having land of their own; the representatives of scienceconsidered they would lose caste if another of their number took upfarming.
In 1912 I happened to be on tour in the United Provinces when the mattercame up for final decision. The Director of Agriculture asked my advice.I strongly supported Clarke's proposal and assured the authorities thatgreat things would result if they gave their agricultural chemist thebest farm they could, and then left him alone to work out his ownsalvation. This carried the day; a special sugar-cane farm wasestablished in 1912 near Shahjahanpur on the bank of the Kanout riverand on one of the main roads leading into the town. From 1912 to 1931,an unbroken period of nineteen years, Clarke remained in charge ofShahjahanpur in addition to the three posts he held: AgriculturalChemist (1907-21), Principal of the Agricultural College (1919-21), andDirector of Agriculture (1921-31). From 1912 to 1921 he was there nearlyevery week-end. Until he became Director of Agriculture in 1921, he wasat Shahjahanpur every year from Christmas until March for the sugar-caneharvest and the planting of the next year's crop. It was during theseperiods that he gained a first-hand knowledge of the Indian village, itspeople, its fields, and its agricultural problems, which was to standhim in such good stead when he was called upon to direct theagricultural development of the Provinces in the early years of theMontagu-Chelmsford Reforms.
The sugar-growing tract of northern India, the most important in thecountry, is a broad strip of deep alluvial land about 500 miles inlength skirting the Himalayas. It begins in Bihar; it ends in thePunjab, and reaches its greatest development in the Revenue Divisions ofGorakhpur, Meerut, and Rohilkhand of the United Provinces. The soil iseasily cultivated and is particularly suitable for the root developmentof the sugar-cane. The climate, however, is not particularly favourableas the growing period is so short and confined to the rainy season--thelast half of June, July, August, and September--when the moist tropicalconditions created by the south-west monsoon are established. The rainsare followed by the cold season (October 15th to March 15th) duringwhich very little rain is received. After the middle of March theweather again changes, becoming very hot and dry till the break of therains in June. During the hot weather the cane, which is usually plantedtowards the end of February, has to be irrigated.
When work was started in 1912, the yield of stripped cane on 95 percent. of the sugar-cane area of the United Provinces was only 13 tons tothe acre, producing just over 1 ton of crude sugar (gur). The land wasfallowed during the previous rains and was well prepared for the crop by15 to 20 shallow ploughings with the native plough. As in many otherIndian crops a good balance has been established, as a result ofage-long experience, between the methods of cultivation and the economiccapacity of the indigenous varieties. The methods of cultivation, thenitrogen supply, and the kinds grown were all in correct relation theone to the other. These varieties had been cultivated for at leasttwenty centuries and were thin, short, and very fibrous with juice richin sugar in good seasons. They remind one more of the wild species ofthe genus Saccharum than of the thick sugar-canes found in tropicalcountries. Five or six varieties are grown together, each with a name,usually of Sanskrit origin, denoting their qualities, and each isreadily recognized by the people.
The types of cane grown by the cultivators in the Rohilkhand Divisionwere first separated and an attempt was made to intensify thecultivation of the best. The yield of cane was raised from 13 to 16 tonsper acre without deterioration in the quality of the juice, but furtherintensification did not succeed. As much as 27 tons to the acre wasobtained, but the thin, watery juice contained so little sugar that itwas not worth extracting. The variety and the improved soil conditionswere not in correct relation. The leaf area developed by the indigenousvarieties was insufficient, in the short growing period of North India,to manufacture the cellulose required for the fibre and other tissue ofso large a crop, and enough sugar to make the juice of economic value.This was a most important experiment as it defined the general problemand showed definitely what had to be done. To raise the out-turn ofsugar in the United Provinces, a combination of intensive methods ofcultivation with more efficient varieties, adapted to the very specialclimatic conditions, would be necessary. These two problems were takenup simultaneously: in all the subsequent work the greatest care wastaken to avoid the fragmentation of the factors, a rock on which so muchof the agricultural research of the present day founders.
Attention was then paid to the two chief factors underlying the problem:(1) the discovery of a suitable cane, and (2) the study of intensivecane growing with the object of finding out the maximum yield that couldbe obtained.
The collection of cane varieties at Shahjahanpur included a Javaseedling--POJ 213 which was exactly suited to the local soil and climateand which responded to intensive cultivation. This Java cane was ahybrid. Its pollen parent was the Rohilkhand variety Chunni, which hadbeen given to the Dutch experts, who visited India twenty years earlier,by the Rosa Sugar Factory. Chunni was immune to sereh--a serious diseasethen threatening the sugar industry in Java--and, when crossed with richtropical canes, produced immune or very resistant seedlings of goodquality, widely known throughout the world as POJ (Passoerean Ost-Java)seedlings. POJ 213 proved invaluable during the early stages of theShahjahanpur work. It was readily accepted by the cultivators among whomit was known as 'Java'. A large area was soon grown in Rohilkhand and itsaved the local sugar industry then on the verge of extinction. Mostimportant of all it created an interest in new kinds of sugar-cane andprepared the ground for the great advance, which came a few years laterwhen a Coimbatore seedling--Co 213--raised by the late Dr. Barber,C.I.E.--replaced it.
Clarke had not been long in the United Provinces before he noticed thatthe soil of the Gangetic plain could be handled in much the same way asthat of the Holland Division of Lincolnshire, where the intensivecultivation of potatoes had been introduced sixty or seventy yearsbefore and brought to a high state of perfection. Both soils arealluvial though of widely different date. The problems connected withthe intensive cultivation of potatoes in Lincolnshire and sugar-cane inthe United Provinces have a great deal in common. Both crops arepropagated vegetatively, and in both it is a most important point toproduce the soil conditions necessary to develop the young plantquickly, so that it is ready to manufacture and store a large quantityof carbohydrate in a short period of favourable climatic conditions.When the intensification of sugar-cane cultivation was begun atShahjahanpur, the lessons learnt in the potato fields of Lincolnshirewere at once applied. During the fallow which preceded the crop the landwas cultivated and, as soon as possible after the retreat of themonsoon, the farm-yard manure was put on and ploughed in. This gave thetime necessary for a valuable supply of humus to be formed in the toplayer of the soil. The sugar-cane was planted in shallow trenches 2 feetwide, 4 feet from centre to centre. The soil from each trench wasremoved to a depth of 6 inches and piled on the 2 feet space leftbetween each two trenches, the whole making a series of ridges asillustrated in Fig. 6.
FIG. 6. Trench System at Shahjahanpur
As soon as the trenches are made in November, they are dug with a localtool (kasi) to a further depth of 9 inches, and the oilcake, or whateverconcentrated organic manure is available, is thoroughly mixed with thesoil of the floor of the trenches and allowed to remain, with occasionaldigging, till planting time in February. The thorough cultivation andmanuring of the trenches at least two months, and preferably three,before the canes are planted, proved to be essential if the best resultswere to be obtained. Readers familiar with the methods of sugar-canecultivation in Java will at once realize that this Shahjahanpur methodis a definite advance on that in use in Java, in that the use ofartificials is entirely unnecessary. Hand-made trenches always givebetter yields than those made by mechanical means--an interestingresult, which has often been obtained elsewhere, but which has neverbeen adequately explained. It may be that speed in cultivation is anadverse factor in the production of tilth.
At first heavy dressings of organic manures like castor cake meal at therate of about 2,870 lb. to the acre were used in the trenches. Thiscontains about 4.5 per cent. of nitrogen, so that 2,870 lb. isequivalent to 130 lb. of nitrogen to the acre. This heavy manuring,however, was soon reduced after the introduction of the method ofgreen-manuring described below. When green-manuring was properly carriedout, the dung applied before making the trenches could be reduced tohalf or even less.
At first the trenches were irrigated about a month before planting andlightly cultivated when dry enough. These operations promoted the decayof the manure, and allowed for abundant soil aeration. The canes wereplanted in the freshly dug moist rich earth towards the end of February.Later this preliminary watering was dispensed with. The cuttings wereplanted in the dry earth, and lightly watered the next day. This savedone irrigation and proved to be an effective protection from white ants(Termites), which often attacked the cane cuttings unless these startedgrowth at once and the young plants quickly established themselves. Fourlight waterings, followed in every case by surface cultivation, werenecessary before the break of the monsoon in June. As soon as the youngcanes were about 2 feet high, and were filtering vigorously, thetrenches were gradually filled in, beginning about the middle of May andcompleting the operation by the end of the month. Before the rainsbegan, the earthing up of the canes commenced. It was completed by aboutthe middle of July (Fig. 7).
FIG. 7. Earthing up sugar-cane at Shahjahanpur, July 10th, 1919
One of the consequences of earthing up canes, grown in fertile soil,observed by Clarke was the copious development of fungi which wereplainly visible as threads of white mycelium all through the soil of theridges, and particularly round the active roots. As the sugar-cane is amycorrhiza-former there is little doubt that the mycelium, observed insuch quantities, was connected with the mycorrhizal association. Theprovision of all the factors needed for this association--humus,aeration, moisture, and a constant supply of active roots--probablyexplains why such good results have always followed this method ofgrowing the cane and why the crops are so healthy. When grown on theflat, want of soil aeration would always be a limiting factor in thefull establishment of the mycorrhiza.
The operation of earthing up serves four purposes: (1) the succession ofnew roots, arising from the lower nodes, thoroughly combs the highlyaerated and fertile soil of the ridges; (2) the conditions suitable forthe development of the mycorrhizal association are provided; (3) thestanding power of the canes during the rains is vastly improved; and (4)the excessive development of colloids in the surface soil is prevented.If this earthing up is omitted, a heavy crop of cane is almost alwayslevelled by the monsoon gales; crops which fall down during the rainsnever give the much-prized light coloured crude sugar. The production ofcolloids in the surface soil, when the canes are grown on the flat,always interferes with soil aeration during the period when sugar isbeing formed; crops which ripen under conditions of poor soil aerationnever give the maximum yield.
An essential factor in obtaining the highest efficiency in this ridgingsystem is good surface drainage. This was achieved by lowering the earthroads and paths which, when grassed over, acted as very efficient drainsfor carrying off the excess rainfall during the monsoon. The surfacewater collected in the trenches which were suitably connected with thesystem of lowered paths and roads. By this means the drainage creptaway, in thin sheets of clear water, to the river without any loss oforganic matter or of fine soil particles. The grass carpet acted as amost efficient filter and was at the same time manured. The roadsyielded good crops of grass for the work cattle. This simple deviceshould be utilized wherever possible to prevent both water-logging andsoil erosion.
The results of this intensive method of cane cultivation--based on thegrowth of efficient varieties, proper soil aeration, good surfacedrainage, carefully controlled irrigation, and an adequate supply oforganic matter--were astounding. In place of 13 tons of cane and justover a ton of sugar per acre, a yield of just over or just under 36 tonsof cane and 3-1/2 tons of sugar per acre was obtained for a period oftwenty years--year in and year out. These are the figures for the farmas a whole. The yield of sugar had been trebled. Such a result hasrarely been obtained for any crop in so short a time and by such simplemeans. In a few cases yields as high as 44 tons of cane and 4-1/2 tonsof sugar were obtained, figures which probably represent the highestpossible production in the climate of the United Provinces.
In working out this method of cane growing in northern India, twocritical periods in sugar production were observed: (1) May and earlyJune when the tillers and root system are developing, and (2) August andSeptember when the main storage of sugar takes place. A check receivedat either of these periods permanently reduces the yield. The acre yieldof sugar is positively and closely correlated with the amount of nitratenitrogen in the soil during the first period and with soil moisture,soil aeration, and atmospheric humidity in the second period. Anyimprovement in cane growing must therefore take into account these twoprinciples.
A new method of intensive cane cultivation had been devised and put intosuccessful practice on a field scale at a State Experiment Station; thefirst step in improving sugar production had been taken. It was nownecessary to fit this advance into a system of agriculture made up of amultitude of small holdings, varying from an average of 4 acres in theeastern districts to 8 acres in the western half of the province. Eachholding is not only minute but it is divided into tiny fields, scatteredover the village area, which is by no means uniform in fertility.Moreover, the farmers of these small holdings possess practically nocapital for investment in intensive agriculture. How could the averagecultivator obtain the necessary manure? The solution of this problementailed a detailed study of the nitrogen cycle on the Gangeticalluvium, the relation between climate, methods of cultivation, and theaccumulation of soil nitrate as well as the discovery of what amounts toa new method of green-manuring for sugar-cane. These investigations wereset in motion the moment the possibilities of intensive cane growingbecame apparent.
The study of the nitrogen cycle, in any locality, naturally includes anintimate acquaintance with the local agriculture. The outstandingfeature of the agricultural year in the United Provinces is the rapiditywith which the seasons change, and the wide variation in theircharacter. The most important of these abrupt transitions are: (1)change from the excessive dryness and high temperatures of April, May,and early June to the moist tropical conditions which set in when thesummer crops are sown at the end of June, immediately after the break ofthe southwest monsoon, and (2) the sudden transition from high humidity,high temperature, and a saturated condition of the soil, at the end ofthe monsoon in September, to the dry temperate conditions which obtainwhen the autumn sowings of food crops take place in October. Thesesudden seasonal changes impose definite limits on what can be done toincrease production. There is very little time for the preparation ofthe land, or for the manufacture of plant food by biological agencies;the period of active growth of the crop is severely limited. The formerinfluences the methods of cultivation and manuring; the latter theselection of varieties. The wide difference between the two agriculturalseasons in the United Provinces is best realized in the autumn (Novemberand December), when crops of ripening cane and growing wheat are to beseen side by side in adjacent fields.
How do the summer and autumn crops, often raised in this area underextensive methods, manage to obtain a supply of nitrate without anyadded manure, and how is it that the soil fertility of the Gangeticalluvium remains so constant? To begin to answer these questions, soilborings from a typical unmanured area--fallowed after the wheat cropwhich was removed in April--were systematically examined and the nitricnitrogen estimated directly by Schloesing's method.
PLATE VII. Nitrate Accumulation in the Gangetic Alluvium
The results, as well as the details of temperature and rainfall, aregiven in Plate VII. The curve brings out clearly: (1) the large andrapid formation of nitrate as the temperature rises in February andMarch, just at the time when the young sugar-cane plant takes in itssupply of nitrogen, (2) the almost complete disappearance of nitratesfrom the soil after the first falls of heavy rain--these are partlywashed out and partly immobilized by fungous growth, provided the humuscontent of the soil has been maintained, (3) the absence ofnitrification in the saturated soil during the monsoon, (4) anotheraccumulation of nitrate (less rapid and less in quantity than in thespring) which occurs in the autumn, following the drying of the soil atthe end of the rains, combined with improved aeration, the result offrequent surface cultivation. Five ploughings to a depth of 3 inches,followed by the levelling beam, were given between September 25th andNovember 31st. These accumulations, obviously the result of biologicalprocesses, fit in with the quantitative requirements of the summer andautumn crops, which need immediate supplies of nitrogen as soon as theseed germinates.
When we compare these results on nitrate accumulation with what theIndian cultivator is doing, we are lost in admiration of the way he setsabout his task. With no help from science, and by observation alone, hehas in the course of ages adjusted his methods of agriculture to theconservation of soil fertility in a most remarkable manner. He is by nomeans the ignorant and backward villager he is sometimes represented tobe, but among the most economical farmers in the world as far as themanagement of the potent element of fertility--combined nitrogen--goes,and tropical agriculture all over the world has much to learn from him.The sugar grower of the great plains of India cannot take a heavyoverdraft of nitrogen from his soil. He has only a limited store--thesmall current account provided by non-symbiotic nitrogen fixation andthe capital stock of humus needed to maintain the crumb structure andthe general life of the soil. He must make the most of his currentaccount; he dare not utilize any of his capital. He has in the course ofages instinctively devised methods of management which furfil theseconditions. He does not over-cultivate or cultivate at the wrong time.Nothing is done to over-oxidize his precious floating nitrogen or todestroy his capital of humus. He probably does more with a littlenitrogen than any farmer in the world outside China. For countless ageshe has been able to maintain the present standard of fertility.
If the production of sugar was to be raised, obviously the first stepwas to provide more nitrate for the critical growth period of May andJune, when the tillers and root system are developing. The conventionalmethod would be to stimulate the crop by the addition of factory-madeand imported fertilizers such as sulphate of ammonia. There are weightyobjections to such a course. The cultivator could not afford them; thesupply might be cut off in time of war; the effect of adding thesesubstances to the soil would be to upset the balance of soilfertility--the foundation of the Indian Empire--by setting in motionoxidation processes which would eat into India's capital, and burn upthe vital store of soil humus. Increased crops would indeed be obtainedfor a few years, but at what a cost--lowered soil fertility, loweredproduction, inferior quality, diseases of crops, of animals, and of thepopulation, and finally diseases of the soil itself, such as soilerosion and a desert of alkali land! To place in the hands of thecultivator such a means of temporarily increasing his crops would bemore than a mere error of judgement: it would be a crime. The use ofartificials being ruled out altogether, some alternative source ofnitrogen had to be found.
Any intensive method of sugar growing in the United Provinces mustaccomplish two things: (1) the normal accumulations of nitrates in thesoil at the beginning of the rains must be fully utilized, and (2) thecontent of soil organic matter must be raised and the biologicalprocesses speeded up so that these natural accumulations can beincreased.
The problem of making use of the nitrate naturally formed in order toraise the content of organic matter was solved in a very neatfashion--by a new method of green-manuring. The fallow, which ordinarilyprecedes cane, was used to grow a crop of san hemp with the help ofabout 4 tons of farm-yard manure to the acre. This small dressing ofcattle manure had a remarkable effect on the speed of growth and also onthe way the green crop decayed when it was ploughed in. Yields of 8 tonsof green-manure were produced in about 60 days which added nearly 2 tonsof organic matter, or 75 lb. of nitrogen, to each acre. In this way thenitrates accumulated at the break of the rains were absorbed andimmobilized; a large mass of crude organic material was provided by thegreen manure itself and by the small dressing of farm-yard manureapplied before sowing. Sheet composting took place in the surface soil.
The early stages of decomposition need ample moisture. The rainfallafter the green crop was ploughed in was carefully watched. If it wasless than 5 inches in the first fortnight in September, the fields wereirrigated. In this way an abundant fungous growth was secured on thegreen-manure as the land slowly dried. The conversion of the whole ofthe green crop into humus was not complete until the end of November.Nitrification then began, slowly, owing to the low temperatures of thecold weather in North India and at a season when there is little risk ofloss. It was not until the newly planted canes were watered at the endof February and the temperature rose at the beginning of the hot weatherthat all the available nitrogen in the freshly prepared humus wasrapidly nitrified to meet the growing needs of the developing rootsystem of the cane. This means simply that a definite time is requiredfor the formation of humus, whether it takes place in the soil by sheetcomposting or in the compost heap, a longer period being required in thesoil than in the heap. The gradual filling of the trenches and thewatering of the canes during the hot weather continued the nitrificationprocess, which was carried a stage farther by the earthing up of thecanes. The provision of drainage trenches between the rows reduced to aminimum any losses of nitrogen due to poor soil aeration following theformation of soil colloids. The canes were thus provided with amplenitrate throughout the growth period. The conditions necessary for themycorrhizal association were also established.
PLATE VIII. Nitrate Accumulation, Green-Manure Experiement,Shahjahanpur, 1928-9
The effects of green-manuring on the nitrate supply is shown in PlateVIII. It will be seen that the enrichment of the soil with humus hasmarkedly increased the amount of nitrate formed during the crucialperiod (March to June) when the rapidly growing cane absorbs most of itssupplies.
The yields of cane and of raw sugar of twenty-seven randomized plots inthe green-manured and control plots are given below:
Effect of green manuring on sugar-cane
Sugar-cane maunds Raw sugar maunds, Dry matter maunds, (82-2/7 lb.), per acre per acre per acre
Green-manure 847.0 87.0 246.0Control 649.0 67.2 200.1
These control plots are representative of the fertile plots of theShahjahanpur Experiment Station, not of the fields of the cultivators.
The crop in the field is shown in Plate IX. The practical result of thissimple method of intensive cane growing worked out at a profit of 6 poundsan acre. These satisfactory results were reflected in the annual statementof income and expenditure of the Shahjahanpur Experiment Station. Formany years income exceeded expenditure by about 50 per cent.
PLATE IX. Green-manure Experiment, Shahjahanpur, 1928-9
The question therefore of the practical value of the work done at thisStation needed no argument. It was obvious. By the help of green-manurealone, supplemented by a small dressing of cattle dung, the yield ofcane was raised from 13 to over 30 tons to the acre; the yield of sugarfrom 1 ton to over 3 tons.
The effect of the intensive cultivation of sugar-cane is not confined tothat crop. The residual fertility and the deep cultivation of thetrenches enabled bumper crops of Pusa wheat and gram--the two rotationcrops grown with cane at Shahjahanpur--to be obtained. These were morethan three times the average yields obtained by the cultivators. In onecase in a field of 31 acres, Pusa 12 wheat gave 35 maunds to the acrewith one irrigation of 4 inches in November. The preceding cane crop wasAshy Mauritius, which yielded 34.7 tons to the acre.
In the early days of the Shahjahanpur farm the effect of the canetrenches on the following wheat crop was very pronounced. The surface ofthe wheat fields resembled a sheet of corrugated iron, the ridgescorresponding to the trenches. After a few sugar crops this conditionpassed off, and the wheat appeared uniform; all the land had been raisedto the new level of fertility.
It is now possible to record the various stages passed through in thisstudy of intensive sugar production:
1. The unimproved crop in an average year yielded 350 maunds per acre (1maund = 82-1/7 lb.; 27.2 maunds = 1 ton).
2. The best indigenous varieties, grown at their maximum capacity withslightly deeper ploughing than the cultivator gives and a small quantityof manure, gave 450 maunds per acre.
3. The introduction of new varieties like POJ 213 and Co 213, grown onthe flat with the same cultivation as (2) above, gave 600 maunds peracre. The increment due to variety was therefore 150 mounds per acre(600-450).
The use of new varieties plus green-manure on the flat without trenchesyielded 800 maunds per acre. The increment due to green-manure wastherefore 200 maunds per acre (800-600).
Intensive cultivation in trenches, with green-manure plus the manuringof the trenches with castor cake meal at the rate of 1,640 lb. per acre,yielded 1,000 maunds per acre. The increment due to improved soilaeration and an adequate supply of humus in the trenches was therefore200 maunds per acre (1,000-800).
The very highest yield ever obtained at Shahjahanpur by the use of (5)above was 1,200 maunds per acre. The additional increment, when all thefactors were functioning at or near their optima was 200 maunds per acre(1,200--1,000).
It will be seen that a combination of variety, green manuring, andcorrect soil management, including the manuring of the trenches, added650 maunds per acre (1,000-350) and that increases of 850 maunds peracre are possible (1,200-350). In the intensive trench method the plantattains an exceptionally high efficiency in the synthesis ofcarbohydrates. In an out-turn test at Shahjahanpur 1,200 maunds ofstripped cane per acre contained 17 per cent. of fibre (mostly purecellulose), 12 per cent. of sucrose, and 1 per cent. of invert sugar.The total quantity of carbohydrate synthesized per acre in about fourmonths of active growth was 204 maunds of cellulose, 144 maunds ofsucrose, and 12 maunds of invert sugar; in all 360 maunds (13.2 tons)per acre of carbohydrates. This means 3.3 tons per acre during theperiod of active growth when every assistance as regards choice ofvariety, soil fertility, and soil management had been provided.
We have in these Shahjahanpur results a perfect example of themanufacture of humus by means of a green-manure crop and its utilizationafterwards. Success depends on two things: (1) a knowledge of thenitrogen cycle and of the conditions under which humus is manufacturedand utilized, and (2) an effective agricultural technique based on thesebiological principles.
The stage was now set for getting the Shahjahanpur results taken up bythe cultivators. Two questions had to be settled:
1. Should an attempt be made to introduce the full Shahjahanpurmethods--improved green-manuring, manured trenches, and newvarieties--or should a beginning be made with green-manuring plus newvarieties with or without trenches according to circumstances? It wasfinally decided to introduce the new variety along with the new methodof green-manuring and to omit the trenches. This decision was madebecause of the scarcity of manure for the full Shahjahanpur method. Thisdifficulty, however, was removed in 1931, the year Clarke left India,with the introduction of the Indore Process, which could have providedevery village with an adequate supply of manure for intensive methods.
2. Should a large organization be created for bringing the results tothe notice of the villagers? At this point the Agricultural Departmentwas transferred to the control of an Indian Minister, and Clarke becameDirector of Agriculture in the United Provinces and a member of theLegislative Council, offices which he held with short temporary breaksfor ten years. He was thus provided with administrative powers fordeveloping to the full the results of his work as a scientificinvestigator. The first two Ministers under whom he served, Mr. C. Y.Chintamani (now Sir Chirravoori) and the Nawab of Chhatari, though ofwidely different political views, were in complete agreement regardingthe necessity of agricultural development and both gave theirunqualified support to the proposals which were placed before them,while in the Council itself members of every shade of opinion, from theextreme Left to the extreme Right, demanded a large extension ofagricultural work. The annual debate on the agricultural budget was oneof the events of the year. From 1921 to 1931 the financial proposals ofGovernment for agricultural improvement were passed without an adversevote of any kind. This was incidentally an example of the success thatcan be obtained under a popular Government in India by a Department whenit is backed by efficient technical work. A large number of Members ofthe Council were influential landlords, deeply interested in thedevelopment of the country-side, and they, and many others outside theCouncil, were anxious to take up something of practical value. It wastherefore decided to start, in the main sugar-growing areas, State-aidedprivate farms for the purpose of demonstrating the new methods ofgrowing cane and providing the large quantity of planting materialrequired for the extension of the area under the new varieties.
The amount of aid given by the State was small, about Rs. 2,000 to Rs.3,000 for every farm. An agreement was entered into, between thelandlords and the Agricultural Department, by which the former agreed toput down a certain area under Co 213, to green-manure the land and toconduct the cultivation on Shahjahanpur lines. Cuttings were to besupplied to the locality at a certain fixed rate. In this way theexample and influence of the landlords was secured at very small cost.At the same time the hold of the Agricultural Department on thecountry-side was increased and strengthened--the landlords became to allintents and purposes an essential portion of the higher staff of theAgricultural Department. They differed, however, from the ordinaryDistrict staff in two important respects: (1) they possessed aninfluence far surpassing that of the ablest members of the AgriculturalDepartment; (2) they were unofficial and unpaid.
The contribution of the Indian landowners to this work was of thegreatest importance. Without their active support and their publicspirit in opening farms, and thus setting up a multitude of localcentres for demonstrating on a practical scale the new method of sugarproduction, and at the same time providing the material for planting ata low rate, the Agricultural Department would have had to fall back onitself for getting the improvements taken up. In place of thedemonstration farms, provided by the landlords at an exceedingly lowcost, the Government would have had to acquire land and start localfarms for advertising the new method and for the supply of plantmaterial. The cost would have been colossal and quite beyond theresources of Government. In place of the influence and personal interestof the natural leaders of the country-side, the Agricultural Departmentwould have had to rely on the work of a host of low-paid subordinates,and would have had to increase its inspecting staff out of allknowledge. An unwieldy and expensive organization would have been theresult. All this was rendered unnecessary by the admirable system ofprivate farms. The idea of using the landlords in agriculture began inOudh in 1914, when a number of private farms were started on the estatesof the Talukdars for demonstrating the value of the new Pusa wheats andfor producing the large quantities of seed needed. Clarke extended thisidea to all parts of the Provinces, and showed how the results obtainedat one experimental farm could be expanded rapidly and effectively byenlisting the active help of the landowners. He provided them with anopportunity, eagerly taken up, of showing their value to thecommunity--that of leadership in developing the country-side bypractical examples of better agriculture which their tenants andneighbours could copy. Landlords all the world over will act in asimilar way once the Agricultural Departments can provide them withresults of real value.
The magnitude of these operations and the speed with which they wereconducted will be obvious from the following summary of the finalresults. In 1916-17 Clarke received about 20 lb. of cuttings of Co 213from Coimbatore for trial. In 1934-5, 33,000,000 tons of this varietywere produced in the United Provinces. The value of the crop of Co 213cane to the cultivator, at the low minimum rate fixed by Government forsugar-cane under the Sugar-Cane Act of 1934, was over 20,000,000 pounds,more than half of which was entirely new wealth. The value of the sugarwhich could be manufactured from this was 42,000,000 pounds. A large sumwas distributed in factory wages, salaries, and dividends, to say nothingof the benefit to the British engineering trade and the effect onemployment in Great Britain of orders for over 10,000,000 pounds worth ofmachinery for new factories. There was no question of glutting anover-stocked market in India. All the additional sugar and sugarproducts were readily absorbed by the local markets.
Here we have a successful effort in directed economy--the development ofimperial resources by simple technical improvements in agriculture,rendered possible by the protection of a valuable imperial market by astraight tariff.
Since Clarke retired from the Indian Agricultural Department, two newfactors--both favourable--have been in operation, which make it easy tofollow up this initial success. The difficulty of producing enough humusin the villages for the trench system has been removed by the Indoresystem of composting. Irrigation has been improved in the sugar-growingtracts by the completion of the Sarda Canal and the provision of cheapelectric power for raising water from wells. The two essentials forintensive agriculture--humus and water--are now available. Before long adetailed account of the progress made by the introduction of the fullShahjahanpur method will no doubt be available. The story begun in thischapter can then be carried on another stage. It will make interestingand stimulating reading.
CLARKE, G., BAYERJEE, S. C., NAIB HUSAIN, M., and QAYUM, A.'Nitrate Fluctuations in the Gangetic Alluvium,and Some Aspects of the Nitrogen Problem in India', Agricultural Journalof India, xvii, 1922, p. 463.
CLARKE, G. 'Some Aspects of Soil Improvement in Relation to CropProduction', Proc. of The Seventeenth Indian Science Congress,Asiatic Society of Bengal, Calcutta, 1930, p. 23.
PART V CONCLUSIONS AND SUGGESTIONS
A FINAL SURVEY
The capital of the nations which is real, permanent, and independent ofeverything except a market for the products of farming, is the soil. Toutilize and also to safeguard this important possession the maintenanceof fertility is essential.
In the consideration of soil fertility many things besides agricultureproper are involved--finance, industry, public health, the efficiency ofthe population, and the future of civilization. In this book an attempthas been made to deal with the soil in its wider aspects, while devotingdue attention to the technical side of the subject.
The Industrial Revolution, by creating a new hunger--that of themachine--and a vast increase in the urban population, has encroachedseriously on the world's store of fertility. A rapid transfer of thesoil's capital is taking place. This expansion in manufacture and inpopulation would have made little or no difference had the wasteproducts of the factory and the town been faithfully returned to theland. But this has not been done. Instead, the first principle ofagriculture has been disregarded: growth has been speeded up, butnothing has been done to accelerate decay. Farming has becomeunbalanced. The gap between the two halves of the wheel of life has beenleft unbridged, or it has been filled by a substitute in the shape ofartificial manures. The soils of the world are either being worn out andleft in ruins, or are being slowly poisoned. All over the world ourcapital is being squandered. The restoration and maintenance of soilfertility has become a universal problem.
The outward and visible sign of the destruction of soil is the speed atwhich the menace of soil erosion is growing. The transfer of capital, inthe shape of soil fertility, to the profit and loss account ofagriculture is being followed by the bankruptcy of the land. The onlyway this destructive process can be arrested is by restoring thefertility of each field of the catchment area of the rivers which areafflicted by this disease of civilization. This formidable task is goingto put some of our oversea administrations to a very severe test.
The slow poisoning of the life of the soil by artificial manures is oneof the greatest calamities which has befallen agriculture and mankind.The responsibility for this disaster must be shared equally by thedisciples of Liebig and by the economic system under which we areliving. The experiments of the Broadbalk field showed that increasedcrops could be obtained by the skilful use of chemicals. Industry atonce manufactured these manures and organized their sale.
The flooding of the English market with cheap food, grown anywhere andanyhow, forced the farmers of this country to throw to the winds the oldand well-tried principles of mixed farming, and to save themselves frombankruptcy by reducing the cost of production. But this temporarysalvation was paid for by loss of fertility. Mother earth has recordedher disapproval by the steady growth of disease in crops, animals, andmankind. The spraying machine was called in to protect the plant;vaccines and serums the animal; in the last resort the afflicted livestock are slaughtered and burnt. This policy is failing before our eyes.The population, fed on improperly grown food, has to be bolstered up byan expensive system of patent medicines, panel doctors, dispensaries,hospitals, and convalescent homes. A C3 population is being created.
The situation can only be saved by the community as a whole. The firststep is to convince it of the danger and to show the road out of thisimpasse. The connexion which exists between a fertile soil and healthycrops, healthy animals and, last but not least, healthy human beingsmust be made known far and wide. As many resident communities aspossible, with sufficient land of their own to produce their vegetables,fruit, milk and milk products, cereals, and meat, must be persuaded tofeed themselves and to demonstrate the results of fresh food raised onfertile soil. An important item in education, both in the home and inthe school, must be the knowledge of the superiority in taste, quality,and keeping power of food, like vegetables and fruit, grown with humus,over produce raised on artificials. The women of England--the mothers ofthe generations of the future--will then exert their influence in foodreform. Foodstuffs will have to be graded, marketed, and retailedaccording to the way the soil is manured. The urban communities (whichin the past have prospered at the expense of the soil) will have to joinforces with rural England (which has suffered from exploitation) inmaking possible the restitution to the country-side of its manurialrights. All connected with the soil--owners, farmers, andlabourers--must be assisted financially to restore the lost fertility.Steps must then be taken to safeguard the land of the Empire from theoperations of finance. This is essential because our greatest possessionis ourselves and because a prosperous and contented country-side is thestrongest possible support for the safeguarding of the country's future.Failure to work out a compromise between the needs of the people and offinance can only end in the ruin of both. The mistakes of ancient Romemust be avoided.
One of the agencies which can assist the land to come into its own isagricultural research. A new type of investigator is needed. Theresearch work of the future must be placed in the hands of a few men andwomen, who have been brought up on the land, who have received afirst-class scientific education, and who have inherited a specialaptitude for practical farming. They must combine in each one of thempractice and science. Travel must be included in their training becausea country like Great Britain, for instance, for reasons of climate andgeology, cannot provide examples of the dramatic way in which the growthfactors operate.
The approach to the problems of farming must be made from the field, notfrom the laboratory. The discovery of the things that matter isthree-quarters of the battle. In this the observant farmer and labourer,who have spent their lives in close contact with Nature, can be of thegreatest help to the investigator. The views of the peasantry in allcountries are worthy of respect; there is always good reason for theirpractices; in matters like the cultivation of mixed crops theythemselves are still the pioneers. Association with the farmer and thelabourer will help research to abandon all false notions of prestige;all ideas of bolstering up their position by methods far too reminiscentof the esoteric priesthoods of the past. All engaged on the land must bebrother cultivators together; the investigator of the future will onlydiffer from the farmer in the possession of an extra implement--science--and in the wider experience which travel confers. The futurestanding of the research worker will depend on success: on abilityto show how good farming can be made still better. The illusionthat the agricultural community will not adopt improvements willdisappear, once the improver can write his message on the land itselfinstead of in the transactions of the learned societies. The naturalleaders of the country-side, as has been abundantly proved in ruralIndia, are only too ready to assist in this work as soon as they areprovided with real results. No special organization, for bringing theresults of the experiment stations to the farmer, is necessary.
The administration of agricultural research must be reformed. The vast,top-heavy, complicated, and expensive structure, which has grown up byaccretion in the British Empire, must be swept away. The time-consumingand ineffective committee must be abolished. The vast volume of printmust be curtailed. The expenditure must be reduced. The dictum of Carrelthat 'the best way to increase the intelligence of scientists would beto reduce their number' must be implemented. The research applied toagriculture must be of the very best. The men and women who are capableof conducting it need no assistance from the administration beyond themeans for their work and protection from interference. One of the chiefduties of the Government will be to prevent the research workersthemselves from creating an organization which will act as a bar toprogress.
The base line of the investigations of the future must be a fertilesoil. The land must be got into good heart to begin with. The responseof the crop and the animal to improved soil conditions must be carefullyobserved. These are our greatest and most profound experts. We mustwatch them at work; we must pose to them simple questions; we must buildup a case on their replies in ways similar to those Charles Darwin usedin his study of the earthworm. Other equally important agencies inresearch are the insects, fungi, and other micro-organisms which attackthe plant and the animal. These are Nature's censors for indicating badfarming. To-day the policy is to destroy these priceless agencies and toperpetuate the inefficient crops and animals they are doing their bestto remove. To-morrow we shall regard them as Nature's professors ofagriculture and as an essential factor in any rational system offarming. Another valuable method of testing our practice is to observethe effect of time on the variety. If it shows a tendency to run out,something is wrong. If it seems to be permanent, our methods arecorrect. The efficiency of the agriculture of the future will thereforebe measured by the reduction in the number of plant breeders. A few onlywill be needed when soils become fertile and remain so.
Nature has provided in the forest an example which can be safely copiedin transforming wastes into humus--the key to prosperity. This is thebasis of the Indore Process. Mixed vegetable and animal wastes can beconverted into humus by fungi and bacteria in ninety days, provided theyare supplied with water, sufficient air, and a base for neutralizingexcessive acidity. As the compost heap is alive, it needs just as muchcare and attention as the live stock on the farm; otherwise humus of thebest quality will not be obtained.
The first step in the manufacture of humus, in countries like GreatBritain, is to reform the manure heap--the weakest link in Westernagriculture. It is biologically unbalanced because the micro-organismsare deprived of two things needed to make humus--cellulose andaufficient air. It is chemically unstable because it cannot hold itselftogether--valuable nitrogen and ammonia are being lost to theatmosphere. The urban centres can help agriculture, and incidentallythemselves, by providing the farmers with pulverized town wastes fordiluting their manure heaps and, by releasing, for agriculture andhorticulture, the vast volumes of humus lying idle in the controlledtips.
The utilization of humus by the crop depends partly on the mycorrhizalassociation--the living fungous bridge which connects soil and sap.Nature has gone to great pains to perfect the work of the green leaf bythe previous digestion of carbohydrates and proteins. We must make thefullest use of this machinery by keeping up the humus content of thesoil. When this is done, quality and health appear in the crop and inthe live stock.
Evidence is accumulating that such healthy produce is an importantfactor in the well-being of mankind. That our own health is notsatisfactory is indicated by one example. Carrel states that in theUnited States alone no less than 700,000,000 pounds a year is spent inmedical care. This sum does not include the loss of efficiency resultingfrom illness. If the restitution of the manurial rights of the soils ofthe United States can avoid even a quarter of this heavy burden, itsimportance to the community and to the future of the American peopleneeds no argument. The prophet is always at the mercy of events;nevertheless, I venture to conclude this book with the forecast that atleast half the illnesses of mankind will disappear once our foodsupplies are raised from fertile soil and consumed in a fresh condition.
COMPOST MANUFACTURE ON A TEA ESTATE IN BENGAL
The Gandrapara Tea Estate is situated about 5 miles south of thefoothills of the Himalayas in North-East India in the district calledthe Dooars (the doors of Bhutan). The Estate covers 2,796 acres, ofwhich 1,242 are under tea, and it includes 10 acres of tea seed bushes.There are also paddy or rice land, fuel reserve, thatch reserves,bamboos, tuna oil, and grazing land. The rainfall varies from 85 to 160inches and this amount falls between the middle of April and the middleof October, when it is hot and steamy and everything seems to grow.
The cold-weather months are delightful, but from March till the monsoonbreaks in June the climate is very trying.
There are approximately 2,200 coolies housed on the garden; most ofthese originally came from Nagpur, but have been resident for a numberof years. The Estate is a fairly healthy one, being on a plateau betweenlarge rivers; and there are no streams of any kind near or runningthrough the property. All drainage is taken into a near-by forest andinto waste land. The coolies are provided with houses, water-supply,firewood, medicines, and medical attention free, and when ill they arecared for in the hospital freely. Ante-natal and post-natal casesreceive careful attention and are inspected by the European MedicalOfficer each week and paid a bonus; careful records of babies and theirweights are kept and their feeding studied; the Company providesfeeding-bottles, 'Cow and Gate' food, and other requirements to build upa coming healthy labour force. As we survey all living things on theearth to-day we have little cause to be proud of the use to which wehave put our knowledge of the natural sciences. Soil, plant, animal, andman himself--are they not all ailing under our care?
The tea plant requires nutrition and Sir Albert Howard not only wants toincrease the quality of human food, but in order that it may be ofproper standard, he wants to improve the quality of plant food. That isto say, he considers the fundamental problem is the improvement of thesoil itself--making it healthy and fertile. 'A fertile soil,' he says,'rich in humus, needs nothing more in the way of manure: the croprequires no protection from pests: it looks after itself.' . . .
In 1934 the manufacture of humus on a small scale was instituted underthe 'Indore method' advocated by Sir Albert Howard. The humus ismanufactured from the waste products of tea estates. All availablevegetable matter of every description, such as Ageratum, weeds, thatch,leaves, and so forth, are carefully collected and stacked, put into pitsin layers, sprinkled with urinated earth to which a handful of woodashes has been added, then a layer of broken-up dung, and soiledbedding; the contents are then watered with a fine spray--not too muchwater but well moistened. This charging process is continued till thepit is full to a depth of from 3 to 4 feet, each layer being wateredwith a fine spray as before.
PLATE X: Plan of the Compost Factory, Gandrapara Tea Estate
To do all this it was most necessary to have a central factory, so thatthe work could be controlled and the cost kept as low as possible. Acentral factory was erected; details are given in the plan (Plate X);there are 41 pits each 31 x 15 x 3 feet deep; the roofs over these pitsare 33 by 17 feet, space between sheds 12 feet and between lines ofsheds 30 feet; also between sheds to fencing 30 feet; this allowsmaterials to be carted direct to the pits and also leaves room forfinished material. Water has been laid on, a 2-inch pipe with l-inchstandards and hydrants 54 feet apart, allowing the hose to reach allpits. A fine spreaderjet is used; rain-sprinklers are also employed witha fine spray. The communal cow-sheds are situated adjacent to the humusfactory and are 50 by 15 feet each and can accommodate 200 head ofcattle: the enclosure, 173 by 57 feet, is also used to provide outsidesleeping accommodation; there is a water trough 11 feet 6 inches long by3 feet wide to provide water for the animals at all times; the livinghouses of the cowherds are near to the site. An office, store, andchowkidar's house are in the factory enclosure. The main cart-road tothe lines runs parallel with the enclosure and during the cold weatherall traffic to and from the lines passes over this road, where materialthat requires to be broken down is laid and changed daily as required.Water for the factory has a good head and is plentiful, the main cockfor the supply being controlled from the office on the site. All pitsare numbered, and records of material used in each pit are kept,including cost; turning dates and costs, temperatures, watering andlifting, etc., are kept in detail; weighments are only taken when thehumus is applied so as to ascertain tasks and tons per acre ofapplication to mature tea, nurseries, tung berees, seed-bearing bushes,or weak plants.
The communal cow-sheds and enclosure are bedded with jungle and this isremoved as required for the charging of the pits. I have tried out pitswith brick vents, but I consider that a few hollow bamboos placed in thepits give a better aeration and these vents make it possible to increasethe output per pit, as the fermenting mass can be made 4 to 5 feet deep.Much care has to be taken at the charging of the pits so that notrampling takes place and a large board across the pits saves thecoolies from pressing down the material when charging. At the first turnall woody material that has not broken down by carts passing over it ischopped up by a sharp hoe, thus ensuring that full fermentation may act,and fungous growth is general.
PLATE XI: Above, Covered and uncovered pits. Middle, Roofing a pit.Below, Cutting Ageratum.
With the arrangement of the humus factory compost can be made at anytime of the year, the normal process taking about three months. With thecentral factory much better supervision can be given, and a better classof humus is made. That made outside and alongside the raw material andleft for the rains to break down acts quite well, but the finishedproduct is not nearly so good. It therefore pays to cut and wither thematerial and transport it to the central factory as far as possible.
In the cold weather, a great deal of sheet-composting can be done. Afterpruning, the humus is spread at 5 tons to the acre; and hoed in with theprunings; the bulk of prunings varies, but on some sections up to 16tons per acre have been hoed in with the humus and excellent results arebeing obtained.
On many gardens the supply of available cow-dung manure and greenmaterial is nothing like equal to the demand. Many agriculturists try tomake up the shortage by such expedients as hoeing-in of green crops andthe use of shade trees or any decaying vegetable material that may beobtainable; on practically all gardens some use is made of all forms oforganic materials, and fertility is kept up by these means. It issignificant to note that, for many years now, manufacturers whospecialize in compound manures usually make a range of specialfertilizers that contain an appreciable percentage of humus. Theimportance of supplying soils with the humus they need is obvious. Ihave not space to consider the important question of facilitating thework of the soil-bacteria, but it has to be acknowledged that a supplyof available humus is essential to their well-being and beneficialactivities.
Without the beneficial soil-bacteria there could be no growth, and itfollows that, however correctly we may use chemical fertilizersaccording to some theoretical standard, if there is not in the soil asupply of available humus, there will be disappointing crops, weakbushes, blighted and diseased frames. Also it will be to the good ifevery means whereby humus can be supplied to the soil in a practical andeconomical way can receive the sympathetic attention of those who at thepresent time mould agricultural opinion.
To the above must be added the aeration of the soil by drainage andshade, and I am afraid that many planters and estates do not under standthis most important operation in the cultivation of tea. To maintain thefertility we must have good drainage, shade trees, tillage of variousdescriptions, and manuring. Compost is essential, artificials are atonic, while humus is a food and goes to capital account.
This has been most marked in the season just closing. From October I 938to April 20th, 1939, there had been less than 1-1/2 inches of rain, andconsequently the gardens that suffered most from drought were those thathad little store of organic material--drainage, feeding of the soil, andestablishment of shade trees being at fault.
Coolies are allowed to keep their own animals, which graze free on theCompany's land, and the following census gives an idea of what is on theproperty: 133 buffaloes, 115 bullocks, 612 cows, 466 calves, 21 ponies,384 goats, 64 pigs: in all, 1,795 animals.
During the past two years practically no chemical manure or sprays fordisease and pest-control have been used, the output for the past year ofhumus was about 3,085 tons, while a further 1,270 tons of forestleaf-mould have been applied. The cost of making and applying the formeris Rs.2/8/6 per ton, and cost and applying forest leaf-mould is RS.1/3/9per ton
The conversion of vegetable and animal waste into humus has beenfollowed by a definite improvement in soil-fertility.
The return to the soil of all organic waste in a natural cycle isconsidered by many scientists to be the mode of obtaining thebest-tasting tea, and to resisting pest and disease.
Nature's way, they claim, is still the best way.
GANDRAPARA TEA ESTATE,BANARHAT, P.O.J.C. WATSON.18 November, 1939.
COMPOST MAKING AT CHIPOLI, SOUTHERN RHODESIA
Compost of a kind has been made at Chipoli for a number of years, buttill Sir Albert Howard's methods were mastered some years ago the wasteof material had been considerable, the product unsatisfactory, and thecost, in comparison with that now produced, high.
Deep pits were used and the process was chicfly carried out underanaerobic conditions, with the result that it took many months and mostof the nitrogen was lost. Farm-yard manure was stored either in thestockyards or in large solid heaps, with the result that when the masswas broken up to be carted on to the fields most of the nitrogen hadbeen lost, and much of the coarse grass, reeds, and similar matter usedfor bedding remained fairly well preserved, much as bog oak in the mud,and the process of decomposition remained to be completed in the soilwith the growing crop, much to the detriment of the latter.
At Chipoli the compost-field has been laid out on the same principle asat Indore. Water is laid on and standpipes are situated at regularintervals. One-inch rubber hose-pipes are used to spray the water on tothe compost heaps. With this arrangement compost can be made at any timeof the year, the normal process taking almost exactly three months.
It has been claimed that it is cheaper to make compost in heapsalongside the lands where the raw material is grown and to rely on therains for the water. If the rains are regular this acts quite well; butthis is not always the case, and with the interruption of the processthe finished product is not so good. Another objection to making compostaway from an artificial water-supply is that the material to becomposted cannot be used the same season, with the result that a year islost. I have known seasons when the sequence of the rainfall has beenunsuitable for the completion of the manufacture, with the result thatthe position of a farmer who had been relying on this method for theprovision of compost to maintain the fertility of his lands would beserious. The cost of a water-supply is a small insurance premium to payfor certainty of manufacture.
I find pits unnecessary even in the hot weather. If the heaps aresprayed over every day it is quite enough to maintain the correct degreeof moisture, and one native can easily control 500 tons. To apply waterin buckets is not satisfactory: the material does not get a uniformwetting--too much is thrown on one place and too little on another.
As the heaps are being turned, a controlled spray keeps the moisturecontent correct.
The question of cost is raised against the central manufactory. I am ofopinion that the small extra cost of transportation is far more thanoffset by better supervision and the control of the process. The cost ofmoving the raw material can be reduced by stacking the san hemp, orwhatever is being used, in heaps, and allowing it to rot to a certainextent. This considerably reduces the bulk.
The material used for making compost at Chipoli is mostly coarse veltgrass which is cut from river banks, dongas, and wherever it isavailable; next in bulk is san hemp grown for the purpose, and thenrushes, crop wastes, weeds, garden refuse, and so forth.
Compost is returned to the san hemp stubble and the land then ploughed.In the past large quantities of san hemp have been ploughed into theland to maintain the humus supply. In some seasons this works quitewell, but in others, owing to unfavourable weather conditions,quantities of unrotted vegetable matter are left on or under thesurface, to be decomposed the following season before a crop can beplanted. By cutting and composting this surface growth and returning itto the land, everything is ready for planting as soon as the rainscommence. Again, compost made from combined animal and vegetable wastehas evidently some great advantage over humus derived from the topgrowth of a green crop only.
In making the heaps, a layer of vegetable waste is put down; the heapsare built about 25 yards long and 15 feet wide. Dung and urine-saturatedbedding is then laid on top and on this is spread the correct quantityof soil and wood-ash; the whole is then wetted from the hose-pipe andthe process repeated till the heap is some 3 feet high. Heatingcommences at once, and after some ten days, when fungous growth hasbecome general, the heap is turned and more water applied if required.Two heaps are made side by side and if the bulk has become reducedconsiderably, as generally happens by the time the third turning is due,the two heaps are thrown into one. This maintains the bulk and soensures that the process goes on properly without any interruption.Should action appear slow at the first turning, compost from anotherheap--which is being turned for the second time and in which action hasbeen normal--is scattered among the material as it is being turned;inoculation thus takes place and the process starts up as it should.
I have found that a mixture of grass and san hemp acts much better thaneither san hemp or grass alone.
It has been the practice to lay coarse material on the roads and toallow wagon traffic to pass over it for some time; this breaks it downand action is much more satisfactory when manufacture commences. Abetter plan is to pass all the raw material through the stock-yards,where it becomes impregnated with urine and dung and gets broken up atthe same time by being trampled. All that is then necessary in makingthe heaps is to mix this material with soil and wood-ash and moisten it.
It has always been the routine to broadcast some form of phosphaticfertilizer on the lands. This is now added direct to the compost heapsand so reaches the fields when the compost is being spread. The cheapestform of manure to be bought locally is bone-meal; besides phosphate thiscontains about 4 per cent. of nitrogen. Dried grass, the chief source ofraw material, contains about one-half per cent. of nitrogen; this isvery low, so that the addition of the extra nitrogen in the bone-mealassists the manufacture, and none of the nitrogen is lost. This additionof bone-meal is simply a local variation and is in no way necessary forthe working of the process.
This year a spell of very wet weather converted the open cattle-yardsinto a quagmire. As soon as possible the sodden bedding and manure wascarted on to the compost field and built into heaps with a liberalinterbedding of soil. The material was so sodden that it packed tightlyand a dark-coloured liquid exuded from the heaps. The material wasturned immediately and more soil added, which absorbed the free liquid.After an interval of three days, a further turning took place and withthis the swarms of flies, which had followed the manure from the yards,disappeared. Heating was slow, so a further turn was given; at each turnthe heaps became more porous; with this last turn, heating became rapidand the fungous growth started, normal compost manufacture havingcommenced. Now that the principle of turning with the consequentaeration is understood, losses which took place in the past throughimproper storage will be avoided. One is reminded of the family middenin countries like Belgium, with their offensive smells and clouds offlies; if the composting principle was understood, what loss could beavoided and how much more sanitary would conditions become!
The chief inquiry with many people before commencing compost making isthat of cost. This largely depends on local conditions. Labour costs andthe ease with which the raw materials can be collected are the chieffactors. I happen to grow tobacco and to use wood as fuel for curing; mytobacco barns are close to the compost field so that my supply ofwood-ash is both plentiful and handy. The stock-yards are situated closeat hand, through which in future it is hoped to pass all the vegetablewastes. It has been found that san hemp hay makes an excellent stockfood; stacks of this will be made alongside the compost field andfeeding pens put up where the working oxen can get a daily ration, therefuse being put on to the heaps.
Compost making has been going on for too short a time here to be able togive definite costs. A particular operation that costs a certain sumthis year may have its cost halved next year as methods of working areimproved. As an approximate indication, however, the following willserve.
On a basis of turning out 1,000 tons of finished compost, collecting allthe raw material and spreading the compost on the field.
For those who do not know, a South African wagon is generally 18 feetlong; it is drawn by a span of sixteen oxen and holds a normal load of 5tons. For carting vegetable wastes I make a framework of gum poles whichsits on the top of the wagon and so greatly increases its carrying powerfor bulky materials. Sometimes two or three such wagons work on compostmaking the same day, and sometimes not any, but an average would be onewagon full time for four months. Such a wagon requires a driver and aleader and two other men for loading and unloading with the help of thedriver and sometimes the leader. Labour for cutting and collecting thecoarse grass, reeds, etc., works out at about ten natives every day fortwo months. The san hemp is cut with a mowing-machine and collected witha sweep, say four natives for one month. As regards the manufactureitself, four natives for five months can attend to everything. Thisgives a total of 1,800 native days. For spreading the finished compostsome people use a manure-spreader, which does an excellent job, but suchan implement would be too slow for us.
PLATE XIII: Compost Making at Chipoli, Southern RhodesiaAbove, General view of composting area.Below, Watering the heaps.
On Chipoli three wagons are used for spreading at the same time; eachwagon carries something over 3 tons of finished compost. Four nativesfill the wagons at the heaps and as soon as a wagon arrives in the fieldit is boarded by four other natives with shovels or forks who spread thecompost on a strip of predetermined width as the wagon moves slowlyalong. On an average, taking adjacent and more remote lands, one wagonmakes eight trips a day; thus with a total of fourteen natives we spreadsome 75 tons of compost a day. Spreading 1,000 tons thus takes 200native days. In other words, the whole operation from cutting the wastematerials to spreading the finished product on the land takes 2,000native days. This means that the work of two natives for one day isrequired for each ton of compost made and spread on the land.
To the above must, of course, be added the upkeep and depreciation onwagons, mowing-machine, etc., when engaged on this work, but this isquite a small item. The ox is not taken into account, as not only doeshe assist in the manufacture by providing waste material, but when histerm of service has come to an end he is fattened up and sold to thebutcher, generally for a sum at least as much as he cost.
My water service, made from material purchased from an old mine, waswritten off after the first season.
I made the statement recently before the Natural Resources Commissionthat, if compost making became general in Southern Rhodesia, theagricultural output of the country could be doubled without any more newland being brought under cultivation.
Last year the bill for artificials on Chipoli was roughly half of whatit used to be, and if the state of the growing crops is any indicationthe out-turn will increase by fifty per cent.
This season compost has been used on citrus, maize, tobacco, monkeynuts, and potatoes. A neighbour was persuaded, somewhat against hiswill, to make some compost; this he did and applied it to land on whichhe planted tobacco: he now tells me that that particular tobacco wasmuch the best on his farm.
Some photographs published in the Rhodesia Agricultural Journal show ina striking manner the drought-resisting properties imparted to landafter being dressed with compost. The maize plants on the land to whichcompost had been added show almost no signs of distress, while thosealongside on land that had no compost are all shrivelled up. Properlymade compost has the property of fixing a certain amount of atmosphericnitrogen. To do this to the best advantage it appears necessary that themanufacture should be carried out as quickly as possible. There must beno interruption, and the material must on no account be allowed to dryout or to become too wet. I am inclined to use more soil than isabsolutely necessary; it costs nothing, and the small extra charge intransport is more than covered by its presence as a form of insuranceagainst any nitrogen that might be given off' which it tends to graspand fix. We at the present stage know little about mycorrhiza, but it isprobable that an excess of soil is not a disadvantage where this isconcerned.
Where the acreage is large and the compost will not go round it all, itis probably better to give a medium dressing to a larger acreage than aheavy dressing to a smaller one. A dressing of about 5 tons to the acreis about the minimum for ordinary crops, but for such things as potatoesand truck crops at least 10 tons to the acre should be given, and, ifavailable, considerably more. It must be borne in mind that much of thesoil in Rhodesia has been so depleted of humus that in order to bring itproperly to life again much heavier dressings of compost will benecessary now than when it has once attained natural conditions.
The more I see of compost-making the more necessary it appears to be tolet the material have continuous access to air. This, as has beenpreviously explained, can be done by frequent turning, and if turnedquickly very little heat need be lost and no interruption in the processtakes place.
An advance to better air-supply would be a series of brick flues underthe heaps. But under my conditions, with the position of the heapscontinually changing and with Scotch carts and heavy wagons continuallymoving among the heaps, the flues would always be getting broken.Six-inch pipes with slots cut in the sides and the piece of metal fromthe slot hinged on one side and turned outwards on each side so as toform an air-space in the compost, with a continual supply of air frominside the pipe, would probably act quite well, the advantage being thatsuch pipes would be portable and would be laid down just before the heapwas about to be built. The disadvantage is, of course, one of cost. Togo even farther, a small oil-driven compressor, such as is used to drivea pneumatic hammer, and mounted on a wheelbarrow or small hand-truck andconnected to a pipe by rubber hose, could be used. The pipe would be,say, 1 inch in diameter and pointed at one end. For a distance ofperhaps 18 inches from the point small holes would be drilled. The pipewould be pushed into the heap at the centre and air pumped in, theoperation being repeated at perhaps distances of 3 feet. A large numberof heaps could be treated with forced aeration in a day, and if thismethod resulted in the fixation of only a few extra pounds of nitrogenper ton it might be well worth while.
This is, however, perhaps going too far at the present stage. The greatbeauty of Sir Albert Howard's method is its simplicity. It can be usedin native villages by primitive people using their own tools equallywell as on the most up-to-date estates using elaborate machinery.
I am glad to say that the Rhodesian Government have laid it down thatcompost-making is to be taught at all native agricultural instructionalcentres. Interest in the matter will gradually awaken. I have alreadyhad old men from neighbouring villages come in to see how manure wasmade from dry grass.
We are on the eve of the compost era. Had its principles been appliedyears ago, the desolation that has taken place in the Middle WesternStates of America could have been avoided. The so-called 'law ofdiminishing returns' is seen to apply only to those who do not reallyunderstand the soil and treat it as Nature meant it to be treated.Rhodesia is fortunately a young country and the destruction of its soilhas not gone very far, comparatively speaking.
If compost making becomes general, which means thorough rebuilding ofthe soil and so providing it with greater fertility, greater power towithstand droughts through its enhanced ability to absorb the rainfall,much of which now runs needlessly to the ocean, a great change in theagricultural outlook will take place. The present system, employed bymany, of mining instead of farming the soil, of stimulating it to thelast extent with artificials, and--when it has been killed--abandoningit, must be exchanged for real soil-building according to Nature'smethods. Only in this way can disaster, examples of which can be seenall round, be avoided, and the land be made to produce what it wasintended to produce before our too clever methods were employed upon it.
J. M. MOUBRAYCHIPOLI SHAMVA,SOUTHERN RHODESIA2 February 1939.
THE MANUFACTURE OF HUMUS FROM THE WASTES OF THE TOWN AND THE VILLAGEBy SIR ALBERT HOWARD, C.I.E., M.A.,Formerly Director of the Institute of Plant Industry,Indore, Central India, and AgriculturalAdviser to Slates in Central India and Rajputana.
The forest suggests the basic principle underlying the correct disposalof town and village wastes in the tropics. The residues of the trees andof the animal life, met with in all woodlands, become mixed on the floorof the forest, and are converted into humus through the agency of fungiand bacteria. The process is sanitary throughout and there is nonuisance of any kind. Nature's method of dealing with forest wastes isto convert them into an essential manure for the trees by means ofcontinuous oxidation. The manufacture of humus from agricultural andurban wastes by the Indore Process depends on the same principle--anadequate supply of oxygen throughout the conversion.
THE INDORE PROCESS
The Indore Process, originally devised for the manufacture of humus fromthe waste products of agriculture, has provided a simple solution forthe sanitary disposal of night soil and town wastes. The method is acomposting process. All interested in tropical hygiene will find adetailed account of the big-chemical principles underlying the IndoreProcess, and of the practical working of the method, in the five paperscited at the end of this note.
HUMUS MANUFACTURE AT TOLLYGUNGE, CALCUTTA
Perhaps the best way of introducing the application of the IndoreProcess to town wastes will be to give an account of the recent workdone by Mr. E. F. Watson, O.B.E., at the Tollygunge Municipalitytrenching ground, near Calcutta.
The conversion of house refuse and night soil into humus is carried outin brick-lined pits, 2 feet deep, the edges of which are protected by abrick kerb. The guard rim is made of two bricks laid flat in cementmortar, two quarter-inch rods in the join serving as reinforcement. Theupper brick should project 1 inch over the pit to form a lip forpreventing the escape of fly larvae. Each compartment of the pit has acapacity of 500 cubic feet and channels for aeration and drainage aremade in the floor. The aeration channels are covered with bricks laidopen-jointed, and are carried up at the ends into chimneys open to thewind. By this means air permeates the fermenting mass from below. At onepoint these channels are continued as a drain to the nearest low-lyingland. It is an advantage when bricking the pits to give a slight slopetowards the aeration channels as this helps in keeping the pits dry inwet weather. The area round the pit is protected by brick soling.Working details of these composting pits are shown in Fig. I.
The method of charging the pits is most important, as success depends oncorrect procedure at this point. To begin with, a cartload of unsortedrefuse is tipped into the pit from the charging platform and spread bydrag rakes (Fig. 9) to make a layer 3 or 4 inches thick. Anothercartload of refuse is then tipped on this layer and raked into a slopereaching from the edge to the middle of the pit and occupying its wholewidth. The surface of this slope is slightly hollowed by raking a littlerefuse from the centre to the sides. A little refuse is also raked on tothe sill at the road edge to receive any night soil spilt on it bytipping. Half a cartload of night soil is then tipped on the slope andwith the moistened refuse below it is drawn by drag-rakes in small lotsuntil the breadth of the pit is covered. This done, the remaininghalf-load of night soil is poured on the freshly exposed surface of theslope and distribution by raking repeated until the slope (and therefuse on the sill) is altogether removed and forms a layer over thewhole of the pit being charged. Another cartload of refuse is thentipped, another slope made, the sill covered, night soil added and rakedaway. The whole group of operations is so repeated until the pit ischarged. This takes 2 days. The top layer of the first day's charge mustbe covered with 2 inches of refuse and left unmixed with the layerbelow. This helps to keep uniform moisture and heat in the mixed chargeand to prevent the access of flies. The last operation on the second dayis to make a vacant space at the end of each pit for subsequent turningand also for assisting drainage after heavy rains. This is done bydrawing up 2 feet of the contents at one end over the rest. The surfaceis then raked level and covered with a thin layer of dry house refuse.
There is no odour from a pit properly filled, because the copiousaeration effectively suppresses all nuisance. Smell, therefore, can bemade use of in the practical control of the work; if there is anynuisance the staff employed is not doing the charging properly. They areeither leaving pockets of night soil or else definite layers of thismaterial, both of which interfere with aeration and so produce smell.
First Turn.--Five days from the start the contents of the pit must beturned. The object of this turn is to complete the mixing and to turninto the middle, and so destroy the fly larvae which have been forced tothe cooler surfaces by the heat of the mass.
The original mixing of the heap, as well as the turning, are best donewith long-handled manure drags by men standing on the division walls oron a rough plank spanning them.
Second Turn. After a further ten days the mass is turned a second time,by which time all trace of night soil will have disappeared.
Watering. In dry weather it may be necessary to sprinkle a little wateron the refuse at each turn. The contents must be kept damp but not wet.
In very wet weather, when the surface of the pits is kept continuallycool by rain, there is much development of fly larvae before the firstturn, but since these cannot escape and are turned into the hot mass anddestroyed before they can emerge as flies, no nuisance results. Flies,therefore, are most useful in providing another means of automaticcontrol.
Ripening of the Compost. After a further two weeks the material isremoved from the pits to the platform for ripening. The whole process,therefore, takes one month. The stacks of ripening compost should be 4feet high, arranged clear of the loading platform on a stacking groundrunning between two lines of pits (Fig. 10). The stacking processpermits of sorting. Any material not sufficiently broken down, such assticks, leather, coco-nut husks, and tin cans are picked out and throwninto an adjacent pit for further treatment. Inert materials such asbrickbats and potsherds are thrown on the roads for metalling.Hand-picking is easy at this stage, as the contents of the pit have beenconverted into a rough, inoffensive compost. The ripening process iscompleted in one month, when the humus can be used either for manuringvacant land or as a top dressing for growing crops.
Cost. The capital cost is very small. A population of 5,000 in Indiayields some 250 cubic feet of house refuse daily, enough to mix with allthe night soil. This will require a compost factory of sixteen pits of500 cubic feet each, one pit being filled in two days (Fig. 10). Withroads, platforms, and tools this costs from Rs. 1,000 to Rs. 1,500. Thedaily output is 150 cubic feet of finished compost, which finds a readysale at Rs. 5 to Rs. 7. At the lower figure the sale proceeds of thefirst year will be about Rs. 1,800. This more than covers the workingexpenses. A factory of this size will need a permanent staff of fivemen.
A SIMPLE INSTALLATION FOR A VILLAGE
When a rural community is too poor to own conservancy carts or toconstruct brick-lined pits, composting can be carried out in an opentrench on any high ground, without the use of partition walls.
The difficulty with unlined pits is the escape of fly larvae which breedin the walls of the trench and in the stacks of ripening compost. Thisdisadvantage can be overcome either by bricking the vertical walls or bykeeping fowls, which thrive on the larvae.
SOME FURTHER DEVELOPMENTS
The Use of Humus in Collecting Night Soil. There is one weak point inthese two applications of the Indore Process to urban wastes. In bothcases night soil is collected, transported, and composted in the crudestate. This gives time for putrefaction to begin and for nuisance todevelop. It can be prevented by the use of humus in the latrine pails,which ensures the oxidation of the night soil from the moment ofdeposition, and so prevents nuisance and the breeding of flies. Thepails should contain at least 3 inches of dry humus when brought intouse each day, and the droppings should be covered with a similar layerof humus when the pails are emptied into the conservancy carts. In thisway putrefaction and smell will be avoided; the composting process willstart in the pails themselves. The use of humus will augment the volumeand weight of the night soil handled, but this increase in the work willbe offset by the greater efficiency of composting, by the suppression ofsmell and flies, and by a considerable reduction in the loss of combinednitrogen.
Composting Night Soil and town Wastes in Small Pits. Night soil can becomposted in small pits without the labour of turning. These pits can beof any convenient size, such as 2 feet by 12 feet and 9 inches deep, andcan be dug in lines (separated by a foot of undisturbed soil) in anyarea devoted to vegetables or crops. Into the floor of the pits a forkis driven deeply and worked from side to side to aerate the subsoil andto provide for drainage after heavy rain. The pits are then one-thirdfilled with town or vegetable waste, or a mixture of both, and thencovered with a thin layer of night soil and compost from the latrinepails. The pit is then nearly filled with more waste, after which thepit is topped up with a 3-inch layer of loose soil. The pit now becomesa small composting chamber, in which the wastes and night soil arerapidly converted into humus without any more attention. After three orfour months the pits will be full of finished compost and alive withearthworms. A mixed crop of maize and some pulse like the pigeon pea(Cajanus indicus) can then be sown on the rows of pits as the rainfallpermits, and gradually earthed up with the surplus soil. The maize willripen first, leaving the land in pigeon pea. The next year the pits canbe repeated in the vacant spaces between the lines of pulse. In twoseasons soil fit for vegetables can be prepared.
Reprinted from a paper read at the Health Congress at the Royal SanitaryInstitute held at Portsmouth from July 11th to 16th, 1938.
HOWARD, A., and WAD, Y. D. The Waste Products of Agriculture: TheirUtilization as Humus. Oxford University Press, 193 I.
JACKSON, F. K., and WAD, Y. D. 'The sanitary Disposal and AgriculturalUtilization of Habitation Wastes by the Indore Method', Indian MedicalGazette, lxix, February 1934.
HOWARD, A. 'The Manufacture of Humus by the Indore Method', Journal ofthe Royal Society of Arts, November 22nd, 1935, and December 18th, 1936.(These papers have been reprinted in pamphlet form and copies can beobtained from The Secretary, Royal Society of Arts, John Street,Adelphi, W.C. 2.)
WATSON, E. F. 'A Boon to Smaller Municipalities: The Disposal of HouseRefuse and Night Soil by the Indore Method', The Commercial andTechnical Journal, Calcutta, October 1936. (This paper is now out ofprint, but the substance has been incorporated in a lecture by SirAlbert Howard to the Ross Institute of Tropical Hygiene on June 17th,1937. Copies can be obtained on application to the lecturer at I4Liskeard Gardens, Blackheath, S.E. 3.)
HOWARD, A. 'Soil Fertility, Nutrition and Health', Chemistry andIndustry, vol. lvi, no. 52, December 25th, 1937.