The Soil and Health
A Study of Organic Agriculture
Sir Albert Howard, a sound hard-headed farmer and honest scientist, worked during the first half of this century, without prejudice or sponsorial obligation, to understand the principles of farming. His findings, and his skill with communication through writings, are felt by many to be the very foundation of all modern thinking with regard to biological farming. His perseverance and political savvy are credited with the beginnings of the “organic” farming and gardening movement. I see him as one of the true GIANTS of pertinent agricultural thought and practice. I am a lifelong aficionado of Howard’s work and seeing my own ideological roots stemming, in part, from “An Agricultural Testament” I was thrilled to happen onto a first edition of another of his books “Soil and Health.” With the aid of the Library of Congress we have discerned that this text is in the public domain. We are hoping and trusting that you will agree with our decision that this material deserves to be reprinted in full and that serialization in Small Farmer’s Journal is appropriate.
Some of you may find this material exhaustive and tedious, maybe even boring, I find it amazing, critically important and provocative. It may be the most significant information we have ever published. It needs to return to print and we are pleased to try. We want to know what you think. LRM
by Sir Albert Howard, C.I.E., M.A.
Author of An Agricultural Testament
Originally published in book form and copyrighted 1947 by the Devin-Adair Company
The earth’s green carpet is the sole source of the food consumed by livestock and mankind. It also furnishes many of the raw materials needed by our factories. The consequence of abusing one of our greatest possessions is disease. This is the punishment meted out by Mother Earth for adopting methods of agriculture which are not in accordance with Nature’s law of return. We can begin to reverse this adverse verdict and transform disease into health by the proper use of the green carpet – by the faithful return to the soil of all available vegetable, animal, and human wastes.
The purpose of this book is threefold: to emphasize the importance of solar energy and the vegetable kingdom in human affairs; to record my own observations and reflections, which have accumulated during some forty-five years, on the occurrence and prevention of disease; to establish the thesis that most of this disease can be traced to an impoverished soil, which then leads to imperfectly synthesized protein in the green leaf and finally to the breakdown of those protective arrangements which Nature has designed for us.
During the course of the campaign for the reform of agriculture, now in active progress all over the world, I have not hesitated to question the soundness of present-day agricultural teaching and research – due to failure to realize that the problems of the farm and garden are biological rather than chemical. It follows, therefore, that the foundations on which the artificial manure and poison spray industries are based are also unsound. As a result of this onslaught, what has been described as the war in the soil has broken out in many countries and continues to spread. The first of the great battles now being fought began in South Africa some ten years ago and has ended in a clear-cut victory for organic farming. In New Zealand the struggle closely follows the course of the South African conflict. The contest in Great Britain and the United States of America has only now emerged from the initial phase of reconnaissance, in the course of which the manifold weaknesses of the fortress to be stormed have been discovered and laid bare.
I am indebted to some hundreds of correspondents all over the world for sending me reports of the observations, experiments, and results which have followed the faithful adoption of Nature’s great law of return. Some of this information is embodied and acknowledged in the pages of this book. A great deal still remains to be summarized and reduced to order – a labour which I hope soon to begin. When it is completed, a vast mass of material will be available which will confirm and extend what is to be found in these pages. Meanwhile a portion of this evidence is being recorded by Dr. Lionel J. Picton, O.B.E., in the News-Letter on Compost issued three times a year by the County Palatine of Chester Local Medical and Panel Committees at Holms Chapel, Cheshire. By this means the story begun in their Medical Testament of 1939 is being continued and the pioneers of organic farming and gardening are kept in touch with events.
The fourth chapter on “The Maintenance of Soil Fertility in Great Britain” is very largely based on the labours of a friend and former colleague, the late Mr. George Clarke, C.I.E., who, a few days before his untimely death in May 1944, sent me the results of his study of the various authorities on the Saxon Conquest, the evolution of the manor, the changes it underwent as the result of the Domesday Book, and the enthronement of the feudal system till the decay of the open-field system and its replacement by enclosure.
The spectacular progress in organic farming and gardening which has taken place in South Africa and Rhodesia during the last few years owes much to the work of Captain Moubray, Mr. J.P.J. van Vuren, and Mr. G.C. Dymond, who have very generously placed their results at my disposal. Captain Moubray and Mr. van Vuren have contributed two valuable appendices, while Mr. Dymond’s pioneering work on virus disease in the cane and on composting at the Springfield Sugar Estate in Natal has been embodied in the text. For the details relating to the breakdown of the cacao industry in Trinidad and on the Gold Coast and for a number of other suggestions on African and West Indian agriculture I am indebted to Dr. H. Martin Leake, formerly Principal of the Imperial College of Tropical Agriculture, Trinidad.
I have been kept in constant touch with the progress of organic farming and gardening in the United States of America by Mr. J.I. Rodale of Emmaus, PA, the editor of Organic Gardening, who has started a movement in the New World which promises soon to become an avalanche. Mr. Rodale was the prime mover in bringing out the first American edition of An Agricultural Testament and is responsible for the simultaneous publication of this present book in the United States and of a special American issue of Lady Eve Balfour’s stimulating work – The Living Soil.
In India I have made full use of the experience of Colonel Sir Edward Hearle Cole, C.B., C.M.G., on the Coleyana Estate in the Punjab, and of Mr. E.F. Watson’s work on the composting of water hyacinth at Barrackpore. Messrs. Walter Duncan & Company have generously permitted Mr. J.C. Watson to contribute an appendix on the remarkable results he has obtained on the Gandrapara Tea Estate in North Bengal. In this fine property India and the rest of the Empire possess a perfect example of the way Nature’s law of return should be obeyed and of what freshly preparedhumus by itself can achieve.
I owe much to a number of the active members of the New Zealand Compost Club, and in particular to its former Honorary Secretary, Mr. T.W.M. Ashby, who have kept me fully informed of the results obtained by this vigorous association. The nutritional results obtained by Dr. G.B. Chapman, the President, at the Mount Albert Grammar School, which show how profoundly the fresh produce of fertile soil influences the health of schoolboys, have been of the greatest use. In Eire the Rev. C.W. Sowby, Warden of the College of St. Columba, Rathfarnham, Co. Dublin, and the Rev. W.S. Airy, Head Master of St. Martin’s School, Sidmouth, have placed at my disposal the results of similar work at their respective schools. These pioneering efforts are certain to be copied and to be developed far and wide. Similar ideas are now being applied to factory canteen meals in Great Britain with great success, as will be evident from what Mr. George Wood has already accomplished at the Co-operative Wholesale Society’s bacon factory at Winsford in Cheshire.
For furnishing full details of a large-scale example of successful mechanized organic farming in this country and of the great possibilities of our almost unused downlands I owe much to Mr. Friend Sykes. The story of Chantry, where the results of humus without any help from artificial manures are written on the land itself, provides a fitting conclusion to this volume.
In the heavy task of getting this book into its final shape I owe much to the care and devotion of my private secretary, Miss Ellinor Kirkham.
AN ADVENTURE IN RESEARCH
My first post was a somewhat unusual one. It included the conventional investigation of plant diseases, but combined these duties with work on general agriculture; officially I was described as Mycologist and Agricultural Lecturer to the Imperial Department of Agriculture for the West Indies.
The headquarters of the department were at Barbados. While I was here provided with a laboratory for investigating the fungous diseases of crops (mycology) and was given special facilities for the study of the sugar-cane, my main work in the Windward and Leeward Islands was much more general – the delivery of lectures on agricultural science to groups of schoolmasters to help them to take up nature study and to make the fullest use of school gardens.
Looking back I can now see where the emphasis of my job rightly lay. In Barbados I was a laboratory hermit, a specialist of specialists, intent on learning more and more about less and less: but in my tours of the various islands I was forced to forget my specialist studies and become interested in the growing of crops, which in these districts were principally cacao, arrowroot, ground nuts, sugar-cane, bananas, limes, oranges, and nutmegs. This contact with the land itself and with the practical men working on it laid the foundations of my knowledge of tropical agriculture.
This dual experience had not long been mine before I became aware of one disconcerting circumstance. I began to detect a fundamental weakness in the organization of that research which constituted officially the more important part of my work. I was an investigator of plant diseases, but I had myself no crops on which I could try out the remedies I advocated: I could not take my own advice before offering it to other people. It was borne in on me that there was a wide chasm between science in the laboratory and practice in the field, and I began to suspect that unless this gap could be bridged no real progress could be made in the control of plant diseases: research and practice would remain apart: mycological work threatened to degenerate into little more than a convenient agency by which – provided I issued a sufficient supply of learned reports fortified by a judicious mixture of scientific jargon – practical difficulties could be side-tracked.
Towards the end of 1902, therefore, I took steps which terminated my appointment and gave me a fresh start. My next post was more promising – that of Botanist to the South-Eastern Agricultural College at Wye in Kent, where in addition to teaching I was placed in charge of the experiments on the growing and drying of hops which had been started by the former Principal, Mr. A.D. (later Sir Daniel) Hall. These experiments brought me in contact with a number of the leading hop growers, notably Mr. Walter (afterwards Sir Walter) Berry, Mr. Alfred Amos, and Colonel Honyball – all of whom spared no pains in helping me to understand the cultivation of this most interesting crop. I began to raise new varieties of hops by hybridization and at once made a significant practical discovery – the almost magical effect of pollination in speeding up the growth and also in increasing the resistance of the developing female flowers (the hops of commerce) to green-fly and mildew (a fungous disease) which often did considerable damage. The significant thing about this work was that I was meeting the practical men on their own ground. Actually their practice – that of eliminating the male plant altogether from their hop gardens – was a wide departure from natural law. My suggestion amounted to a demand that Nature be no longer defied. It was for this reason highly successful. By restoring pollination the health, the rate of growth, and finally the yield of hops were improved. Soon the growers all over the hop-growing areas of England saw to it that their gardens were provided with male hops, which liberated ample pollen just as it was needed.
This, my first piece of really successful work, was done during the summer of 1904 – five years after I began research. It was obtained by happy chance and gave me a glimpse of the way Nature regulates her kingdom: it also did much to strengthen my conviction that the most promising method of dealing with plant diseases lay in prevention – by tuning up agricultural practice. But to continue such work the investigator would need land and hops of his own with complete freedom to grow them in his own way. Such facilities were not available and did not seem possible at Wye.
Then my chance came. Early in 1905 I was offered and accepted the post of Economic Botanist at the Agricultural Research Institute about to be founded by Lor Curzon, the then Viceroy of India, at Pusa in Bengal. On arrival in India in May 1905 the new institute only existed on paper, but an area of about seventy-five acres of land at one end of the Pusa Estate had not yet been allocated. I secured it instantly and spent my first five years in India learning how to grow the crops which it was my duty to improve by modern plant-breeding methods.
It was a decided advantage that officially my work was now no longer concerned merely with the narrow problem of disease. My main duties at Pusa were the improvement of crops and the production of new varieties. Over a period of nineteen years (1905-24) my time was devoted to this task, in the course of which many new types of wheat (including rust-resistant varieties), of tobacco, gram, and linseed were isolated, tested, and widely distributed.
In pursuance of the principle I had adopted of joining practice to my theory, the first step was to grow the crops I had to improve. I determined to do so in close conformity with local methods. Indian agriculture can point to a history of many centuries: there are records of the same rice fields being farmed in north-east India which go back for hundreds of years. What could be more sensible than to watch and learn from an experience which had passed so prolonged a test of time? I therefore set myself to make a preliminary study of Indian agriculture and speedily found my reward.
Now the crops grown by the cultivators in the neighbourhood of Pusa were remarkably free from pests: such things as insecticides and fungicides found no place in this ancient system of cultivation. This was a very striking fact, and I decided to break new ground and try out an idea which had first occurred to me in the West Indies and had forced itself on my attention at Wye, namely, to observe what happened when insect and fungous diseases were left alone and allowed to develop unchecked, indirect methods only, such as improved cultivation and more efficient varieties, being employed to prevent attacks.
In pursuit of this idea I found I could do no better than watch the operations of the peasants as aforesaid and regard them and the pests for the time being as my best instructors.
In order to give my crops every chance of being attacked by parasites nothing was done in the way of direct prevention; no insecticides and fungicides were used; no diseased material was ever destroyed. As my understanding of Indian agriculture progressed and as my practice improved, a marked diminution of disease in my crops occurred. At the end of five years’ tuition under my new professors – the peasants and the pests – the attacks of insects and fungi on all crops whose root systems suited the local soil conditions became negligible. By 1919 I had learnt how to grow healthy crops, practically free from disease, without the 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 modern experiment station.
This preliminary exploration of the ground suggested that the birthright of every crop is health.
In the course of the cultivation of the seventy-five acres at my disposal I had to make use of the ordinary power unit in Indian agriculture which is oxen. It occurred to me that the same practices which had been so successful in the growing of my crops might be worth while if applied to my animals. To carry out such an idea it was necessary to have these work cattle under my own charge, to design their accommodation, and to arrange for their feeding hygiene, and management. At first this was refused, but after persistent importunity backed by the powerful support 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 of six pairs of oxen. I had little to learn in this matter, as I belong to an old agricultural family and was brought up on a farm which had made for itself a local reputation in the management of cattle. My work animals were most carefully selected and everything was done to provide them with suitable housing and with fresh green fodder, silage, and grain, all produced from fertile land. I was naturally intensely interested in watching the reaction of these wellchosen and well-fed oxen to diseases like rinderpest, septicaemia, and foot-and-mouth disease which frequently devastated the countryside. (These epidemics are the result of starvation, due to the intense pressure of the bovine population on the limited food supply.) None of my animals were segregated; none were inoculated; they frequently came in contact with diseased stock. As my small farmyard at Pusa was only separated by a low hedge from one of the large cattle sheds on the Pusa estate, in which outbreaks of foot-and-mouth disease often occurred, I have several times seen my oxen rubbing noses with foot-and-mouth cases. Nothing happened. The healthy, well-fed animals failed to react to this disease exactly as suitable varieties of crops, when properly grown, did to insect and fungous pests – no infection took place. These experiences were afterwards repeated at Indore in Central India, but here I had forty, not twelve, oxen. A more detailed account of the prevention and cure of foot-and-mouth disease is given in a later chapter.
These observations, important as they appeared both at the time and in retrospect, were however only incidental to my main work which was, as already stated, the improvement of the varieties of Indian crops, especially wheat. It was in the testing of the new kinds, which in the case of wheat soon began to spread over some millions of acres of India, that there gradually emerged the principle of which my observations about disease did but supply the first links in evidence: namely, that the foundations of all good cultivation lie not so much in the plant as in the soil itself: there is so intimate a connection between the state of soil, i.e. its fertility, and the growth and health of the plant as to outweigh every other factor. Thus on the capital point of increase of yield, if by improvement in selection and breeding my new special varieties of wheat, etc., might be estimated to produce an increase of 10 to 15 percent, such yields could at once be increased not by this paltry margin, but doubled or even trebled, when the new variety was grown in soil brought up to the highest state of fertility. My results were afterwards amply confirmed by my colleague, the late Mr. George Clarke, C.I.E., who, by building up the humus content of his experiment station at Shahjahanpur in the United Provinces and by adopting simple improvements in cultivation and green-manuring, was able to treble the yields of sugar-cane and wheat.
Between the years 1911 and 1918 my experience was considerably enlarged by the study of the problems underlying irrigation and fruit growing. For this purpose I was provided with a small experimental farm on the loess soils of the Quetta valley in Baluchistan where, till 1918, the summer months were spent. After a supply of moisture had been provided to supplement the scanty winter rainfall, the limiting factors in crop production proved to be soil aeration and the humus content of the land. Failure to maintain aeration was indicated by a disease of the soil itself. The soil flora became anaerobic: alkali salts developed: the land died. The tribesmen kept the alkali condition at bay in their fruit orchards in a very suggestive manner – by means of the deep-rooting system of lucern combined with surface dressings of farmyard manure. Moreover they invariably combined their fruit growing with mixed farming and livestock. Nowhere, as in the West, did one find the whole farm devoted to fruit with no provision for an adequate supply of animal manure. This method of fruit growing was accompanied by an absence of insect and fungoid diseases: spraying machines and poison sprays were unheard of: artificial manures were never used. The local methods of grape growing were also intensely interesting. To save the precious irrigation water and as a protection from the hot, dry winds, the vines were planted in narrow ditches dug on the slopes of the valley and were always manured with farmyard manure. Irrigation was led along the ditches and the vines were supported by the steep sides of the trenches. At first sight all the conditions for insect and fungous diseases seemed to be provided, but the plants were remarkably healthy. I never found even a trace of disease. The quality of the produce was excellent: the varieties grown were those which had been in cultivation in Afghanistan for centuries. No signs of running out were observed. Here were results in disease resistance and in the stability of the variety in striking contrast to those of western Europe, where disease is notorious, the use of artificial manures and poison sprays is universal, and where the running out of the variety is constantly taking place.
These results and observations taken together and prolonged over a period of nineteen years at length indicated what should be the right method of approach to the work I was doing. Improvement of varieties, increased yields, freedom from disease were not distinct problems, but formed parts of one subject and, so to speak, were members one of another, all arising out of the great linkage between the soil, the plant, and the animal. The line of advance lay not in dealing with these factors separately but together. If this were to be the path of progress and if it was useless to proceed except on the basis of crops grown on fertile land, then the first prerequisite for all subsequent work would be just the bringing of the experiment station area to the highest state of fertility and maintaining it in that condition.
This, however, opened up a further problem. The only manure at the command of the Indian cultivator was farmyard manure. Farmyard manure was therefore essential, but even on the experiment stations the supply of this material was always insufficient. The problem was how to increase it in a country where a good deal of the cattle-dung has to be burnt for fuel. No lasting good could be achieved unless this problem were overcome, for no results could be applied to the country at large.
The solution was suggested by the age-long practices of China, where a system of utilizing farm wastes and turning them into humus had been evolved which, if applied to India, would make every Indian holding self-supporting as regards manure. This idea called for investigation.
I now came up against a very great difficulty. Such a problem did not fall within my official sphere of work. It obviously necessitated a great deal of chemical and agricultural investigation under my personal control and complete freedom to study all aspects of the question. But while my idea was taking shape, the organization of agricultural research at Pusa had also developed. A series of watertight compartments – plant breeding, mycology, entomology, bacteriology, agricultural chemistry, and practical agriculture – had become firmly established. Vested interests were created which regarded the organization as more important than its purpose. There was no room in it for a comprehensive study of soil fertility and its many implications by one member of the staff with complete freedom of action. My proposals involved “overlapping,” a defect which was anathema both to the official mind (which controlled finance) and to a research institute subdivided as Pusa always had been.
The obvious course was to leave the institute and to collect the funds to found a new centre where I could follow the gleam unhampered and undisturbed. After a delay of six precious years, 1918-24, the Indore Institute of Plant Industry (at which cotton was the principal crop) was founded, where I was provided with land, ample money, and complete freedom. Now the fundamental factor underlying the problems of Indian cotton was none other than the raising of soil fertility. I might therefore kill two birds with one stone. I could solve the cotton problem if I could increase the amount of farmyard manure for India as a whole.
At Indore I had a considerably larger area at my disposal, namely, 300 acres. From the outset the principles which I had worked out at Pusa were applied to cotton. The results were even better. The yield of cotton was almost trebled and the whole experiment station area stood out from the surrounding countryside by reason of the fine crops grown. Moreover these crops were free from disease, with only two exceptions, during the whole eight years of my work there, exceptions in themselves highly significant. A small field of gram, which had become accidentally water-logged three months before the crop was sown, was, a month after sowing, found to be heavily attacked by the gram caterpillar, the infected areas corresponding with the waterlogged areas with great exactness, while the rest of the plot remained unaffected: the caterpillar did not spread, though nothing was done to check it. In the second case a field of san hemp (Crotalaria juncea, L.), originally intended for greenmanuring, was allowed to flower for seed; after flowering it was smothered in mildew and insect pests and no seed set. Subsequent trials showed that this crop will set seed and be disease free on black soils only if the land is previously well manured with farmyard manure or compost.
These results were progressive confirmation of the principle I was working out – the connection between land in good heart and disease-free crops: they were proof that as soon as land drops below par, disease may set in. The first case showed the supreme importance of keeping the physical texture of the soil right, the second was an interesting example of the refusal of Mother Earth to be overworked, of her unbreakable rule to limit herself strictly to that volume of operations for which she has sufficient reserves: flowers were formed, but seed refused to set and the mildew and insects were called in to remove the imperfect product.
These were the exceptions to prove the rule, for during the eight years of my work at Indore it was assumed by me as a preliminary condition to all experiments that my fields must be fertile. This was brought about by supplying them with heavy dressings of compost made on a simple development of the Chinese system. As I was now free, it was possible for me to make these arrangements on a large scale, and in the course of doing so it seemed well worth while to work out the theory that underlay the empiric Chinese practice. A complete series of experiments and investigations were carried out, establishing the main chemical, physical, and biological processes which go to humus formation in the making of compost. In this work I received valuable help from Mr. Y.D. Wad who was in charge of the chemical side of the investigation. On my retirement from official service in 1931 I assumed that the publication of this joint work in book form would be the last scientific task which I should ever undertake.
It proved instead to be the beginning of a new period which has been based on the long preparation which preceded it: the years of work and experiment carried out in the tropics had gradually but inevitably led me up to the threshold of ideas which embrace and explain the facts and the practices, the theory and also the failures, which had med me in the course of these thirty-two years. Our book on The Waste Products of Agriculture: Their Utilization as Humus, designed to be a practical guide to assist the Indian cotton cultivators, evoked a much wider interest. The so-called Indore Process of making compost was started at a number of centres in other countries and interesting results began to be reported, very much like what I had obtained at Indore.
Two years after publication, in February, 1933, I saw the inception of a compost-making scheme at Colonel Grogan’s estate not far from Nairobi in Kenya Colony. During this visit it first occurred to me gradually to terminate all my other activities and to confine myself to encouraging the pioneers engaged in agriculture all over the world to restore and maintain the fertility of their land. This would involve a campaign to be carried out single-handed at my own expense as no official funds could be expected for a project such as mine. Even if I could have obtained the means needed it would have been necessary to work with research organizations I had long regarded not only as obsolete, but as the perfect means of preventing progress. A soil fertility campaign carried on by a retired official would also throw light on another question, namely, the relative value of complete freedom and independence in getting things done in farming, as compared with the present cumbrous and expensive governmental organization.
By the end of 1933 matters had progressed far enough to introduce the Indore Process to a wider public. This was done by means of two lectures before the Royal Society of Arts in 1933 and 1935, some thousands of extra copies of both of which were distributed all over the world, and subsequent contributions to the Journal of that society, to a German periodical – Der Tropenpflanzer – and a Spanish review – the Revista del Instituto de Defensa del Cafe of Costa Rica. The process became generally known and was found to be a most advantageous proposition in the big plantation industries – coffee, tea, sugar, maize, tobacco, sisal, rice, and vine – yields and quality alike being notably improved. I devoted my energies to advising and assisting those interested, and during this period became greatly indebted to the teaindustry for material help and encouragement.
In 1937 results were reported in the case of tea which were difficult to explain. Single light dressings of Indore compost improved the yield of leaf and increased the resistance of the bush to insect attacks in a way which much surpassed what was normally to be expected from a first application. While considering these cases I happened to read an account of Dr. Rayner’s work on conifers at Wareham in Dorsetshire, where small applications of humus had also produced spectacular results. Normally humus is considered to act on the plant indirectly: the oxidation of the substances composing it ultimately forming salts in the soil, which are then absorbed by the root hairs in the usual processes of nutrition. Was there here, however, something more than this, some direct action having an immediate effect and one very powerful?
Such indeed has proved to be the case and the explanation can now be set forth of the wonderful double process by which Nature causes the plant to draw its nurture from the soil. The mechanism by which living fungous threads (mycelium) invade the cells of the young roots and are gradually digested by these is described in detail in a later chapter. It was this, the mycorrhizal association, which was the explanation of what had happened to the conifers and the tea shrubs, both forest plants, a form of vegetation in which this association of root and fungus has been known for a long time. This direct method of feeding would account for the results observed.
A number of inquiries which I was now able to set on foot revealed the existence of this natural feeding mechanism in plant after plant, where it had hitherto neither been observed nor looked for, but only, be it noted, where there was ample humus in the soil. Where humus was wanting, the mechanism was either absent of ineffective: the plant was limited to the nurture derived by absorption of the salts in the soil solution: it could not draw on these rich living threads, abounding in protein.
The importance of the opening up of this aspect of plant nutrition was quite obvious. Here at last was a full and sufficient explanation of the facts governing the health of plants. From this point on evidence began to accumulate to illumine the new path of inquiry, which in my opinion is destined to lead us a very long way indeed. It is clear that the doubling of the processes of plant nutrition was one of those reserve devices on which rests the permanence and stability of Nature. Plants deprived of the mycorrhizal association continue to exist, but they lose both their power to resist shock and their capacity to reproduce themselves. A new set of facts suddenly fell into place: the running out of varieties, a marked phenomenon of modern agriculture, to answer which new varieties of the important crops have constantly to be bred – hence the modern plant breeding station – could without hesitation be attributed to the continued impoverishment of modern soils owing to the prolonged negligence of the Western farmer to feed his fields with humus. By contrast the maintenance of century-old varieties in the East, so old that in India they bear ancient Sanskrit names, was proof of the unimpaired capacity of the plant to breed in those countries where humus was abundantly supplied.
The mycorrhizal association may not prove to be the only path by which the nitrogen complexes derived from the digestion of proteins reach the sap. Humus also nourishes countless millions of bacteria whose dead bodies leave specks of protein thickly strewn throughout the soil. But these complex bodies are not permanent: they are reduced by other soil organisms to simpler and simpler bodies which finally become mineralized to form the salts taken up by the roots for use in the green leaves. May not some of the very early stages in the oxidation of these specks of protein be absorbed by the root hairs from the soil water? It would seem so, because a few crops exist, like the tomato, which although reacting to humus are not provided with the mycorrhizal association. This matter is discussed in the next chapter.
These results set up a whole train of thought. The problem of disease and health took on a wider scope. In March, 1939, new ground was broken. The Local Medical and Panel Committees of Cheshire, summing up their experience of the working of the National Health Insurance Act for over a quarter of a century in the county, did not hesitate to link up their judgment on the unsatisfactory state of health of the human population under their care with the problem of nutrition, tracing the line of fault right back to an impoverished soil and supporting their contentions by reference to the ideas which I had for some time been advocating. Their arguments were powerfully supported by the results obtained at the Peckham Health Centre and by the work, already published, of Sir Robert McCarrison, which latter told the story from the other side of the world and from a precisely opposite angle – he was able to instance an Eastern people, the Hunzas, who were the direct embodiment of an ideal of health and whose food was derived from soil kept in a state of the highest natural fertility.
By these contemporaneous pioneering efforts the way was blazed for treating the whole problem of health in soil, plant, animal, and man as one great subject, calling for a boldly revised point of view and entirely fresh investigations.
By this time sufficient evidence had accumulated for setting out in book form the case for soil fertility. This was published in June, 1940, by the Oxford University Press under the title of An Agricultural Testament. This book, now in its fourth English and second American edition, set forth the whole gamut of connected problems as far as can at presentbe done – what wider revelations the future holds is not yet fully disclosed. In it I summed up my life’s work and advanced the following views:
- The birthright of all living things is health.
- This law is true for soil, plant, animal, and man: the health of these four is one connected chain.
- Any weakness or defect in the health of any earlier link in the chain is carried on to the next and succeeding links, until it reaches the last, namely, man.
- The widespread vegetable and animal pests and diseases, which are such a bane to modern agriculture, are evidence of a great failure of health in the second (plant) and third (animal) links of the chain.
- The impaired health of human populations (the fourth link) in modern civilized countries is a consequence of this failure in the second and third links.
- This general failure in the last three links is to be attributed to failure in the first link, the soil: the undernourishment of the soil is at the root of all. The failure to maintain a healthy agriculture has largely cancelled out all the advantages we have gained from our improvements in hygiene, in housing, and our medical discoveries.
- To retrace our steps is not really difficult if once we set our minds to the problem. We have to bear in mind Nature’s dictates, and we must conform to her imperial demand: (a) for the return of all wastes to the land; (b) for the mixture of the animal and vegetable existence; (c) for the maintaining of an adequate reserve system of feeding the plant, i.e., we must not interrupt the mycorrhizal association. If we are willing so far to conform to natural law, we shall rapidly reap our reward not only in a flourishing agriculture, but in the immense asset of an abounding health in ourselves and in our children’s children.
These ideas, straightforward as they appear when set forth in the form given above, conflict with a number of vested interests. It has been my self-appointed task during the last few years of my life to join hands with those who are convinced of their truth to fight the forces impeding progress. So large has been the flow of evidence accumulating that in 1941 it was decided to publish a News-Letter on Compost, embodying the most interesting of the facts and opinions reaching me or others in the campaign. The News-Letter, which appears three times a year under the aegis of the Cheshire Local Medical and Panel Committees, has grown from eight to sixty-four pages and is daily gaining new readers.
The general thesis that no one generation has a right to exhaust the soil from which humanity must draw its sustenance has received further powerful support from religious bodies. The clearest short exposition of this idea is contained in one of the five fundamental principles adopted by the recent Malvern Conference of the Christian Churches held with the support of the late Archbishop of Canterbury, Dr. Temple. It is as follows: “The resources of the earth should be used as God’s gifts to the whole human race and used with due consideration for the needs of the present and future generations.”
Food is the chief necessity of life. The plans for social security which are now being discussed merely guarantee to the population a share in a variable and, in present circumstances an uncertain quantity of food, most of it of very doubtful quality. Real security against want and ill health can only be assured by an abundant supply of fresh food properly grown in soil in good heart. The first place in post-war plans of reconstruction must be given to soil fertility in every part of the world. The land of this country and the Colonial Empire, which is the direct responsibility of Parliament, must be raised to a higher level of productivity by a rational system of farming which puts a stop to the exploitation of land for the purpose of profit and takes into account the importance of humus in producing food of good quality. The electorate alone has the power of enforcing this and to do so it must first realize the full implications of the problem.
They and they alone possess the power to insist that every boy and every girl shall enter into their birthright – health, and that efficiency, well-being, and contentment which depend thereon. One of the objects of this book is to show the man in the street how this world of ours can be born again. He can help in this task, which depends at least as much on the plain efforts of the plain man in his own farm, garden, or allotment as on all the expensive paraphernalia, apparatus, and elaboration of the modern scientist: more so in all probability, inasmuch as one small example always outweighs a ton of theory. If this sort of effort can be made and the main outline of the problems at stake are grasped, nothing can stop an immense advance in the well-being of our earth. A healthy population will be no mean achievement, for our greatest possession is ourselves.
The man in the street will have to do three things:
- He must create in his own farm, garden, or allotment examples without end of what a fertile soil can do.
- He must insist that the public meals in which he is directly interested, such as those served in boarding schools, in the canteens of day schools and of factories, in popular restaurants and tea shops, and at the seaside resorts at which he takes his holidays are composed of the fresh produce of fertile soil.
- He must use his vote to compel his various representatives – municipal, county, and parliamentary – to see to it: (a) that the soil of his country is made fertile and maintained in this condition; (b) that the public health system of the future is based on the fresh produce of land in good heart.
This introduction started with the training of an agricultural investigator: it ends with the principles underlying the public health system of tomorrow. It has, therefore, covered much ground in describing what is nothing less than an adventure in scientific research. One lesson must be stressed: The difficulties met with and overcome in the official portion of this journey were not part of the subject investigated. They were man made and created by the research organization itself. More time and energy had to be expended in side-tracking the lets and hindrances freely strewn along the road by the various wellmeaning agencies which controlled discovery than in conducting the investigations themselves. When the day of retirement came, all these obstacles vanished and the delights of complete freedom where enjoyed. Progress was instantly accelerated. Results were soon obtained throughout the length and breadth of the English-speaking world which make crystal clear the great role which soil fertility must play in the future of mankind.
The real Arsenal of Democracy is a fertile soil, the fresh produce of which is the birthright of the nations.
THE PART PLAYED BY SOIL FERTILITY IN AGRICULTURE
THE OPERATIONS OF NATURE
The introduction to this book describes an adventure in agricultural research and records the conclusions reached. If the somewhat unorthodox views set out are sound, they will not stand alone but will be supported and confirmed in a number of directions – by the farming experience of the past and above all by the way Nature, the supreme farmer, manages her kingdom. In this chapter the manner in which she conducts her various agricultural operations will be briefly reviewed. In surveying the significant characteristics of the life – vegetable and animal – met with in Nature particular attention will be paid to the importance of fertility in the soil and to the occurrence and elimination of disease in plants and animals.
What is the character of life on this planet? What are its great qualities? The answer is simple: The outstanding characteristics of Nature are variety and stability.
The variety of the natural life around us is such as to strike even the child’s imagination, who sees in the fields and copses near his home, in the ponds and streams and seaside pools round which he plays, or, if being city-born he be deprived of these delightful playgrounds, even in his poor back-garden or in the neighbouring park, an infinite choice of different flowers and plants and trees, coupled with an animal world full of rich changes and surprises, in fact, a plentitude of the forms of living things constituting the first and probably the most powerful introduction he will ever receive into the nature of the universe of which he is himself a part.
The infinite variety of forms visible to the naked eye is carried much farther by the microscope. When, for example, the green slime in stagnant water is examined, a new world is disclosed – a multitude of simple flowerless plants – the bluegreen and the green algae – always accompanied by the lower forms of animal life. We shall see in a later chapter that on the operations of these green algae the well-being of the rice crop, which nourishes countless millions of the human race, depends. If a fragment of mouldy bread is suitably magnified, members of still another group of flowerless plants, made up of fine, transparent threads entirely devoid of green colouring matter, come into view. These belong to the fungi, a large section of the vegetable kingdom, which are of supreme importance in farming and gardening.
It needs a more refined perception to recognize throughout this stupendous wealth of varying shapes and forms the principle of stability. Yet this principle dominates. It dominates by means of an ever-recurring cycle, a cycle which, repeating itself silently and ceaselessly, ensures the continuation of living matter. This cycle is constituted of the successive and repeated processes of birth, growth, maturity, death, and decay.
An eastern religion calls this cycle the Wheel of Life and no better name could be given to it. The revolutions of this Wheel never falter and are perfect. Death supersedes life and life rices again from what is dead and decayed.
Because we are ourselves alive we are much more conscious of the processes of growth than we are of the processes involved in death and decay. This is perfectly natural and justifiable. Indeed, it is a very powerful instinct in us and a healthy one. Yet, if we are fully grown human beings, our education should have developed in our minds so much of knowledge and reflection as to enable us to grasp intelligently the vast role played in the universe by the processes making up the other or more hidden half of the Wheel. In this respect, however, our general education in the past has been gravely defective partly because science itself has so sadly misled us. Those branches of knowledge dealing with the vegetable and animal kingdoms – botany and zoology – have confined themselves almost entirely to a study of living things and have given little or no attention to what happens to these units of the universe when they die and to the way in which their waste products and remains affect the general environment on which both the plant and animal world depend. When science itself is unbalanced, how can we blame education for omitting in her teaching one of the things that really matter?
For though the phases which are preparatory to life are, as a rule, less obvious than the phases associated with the moment of birth and the periods of growth, they are not less important. If once we can grasp this and think in terms of ever repeated advance and recession, recession and advance, we have a truer view of the universe than if we define death merely as an ending of what has been alive.
Nature herself is never satisfied except by an even balancing of her processes – growth and decay. It is precisely this even balancing which gives her unchallengeable stability. That stability is rock-like. Indeed, this figure of speech is a poor one, for the stability of Nature is far more permanent than anything we can call a rock – rocks being creations which themselves are subject to the great stream of dissolution and rebirth, seeing that they suffer from weathering and are formed again, that they can be changed into other substances and caught up in the grand process of living: they too, as we shall see, are part of the Wheel of Life. However, we may at a first glance omit the changes which affect the inert masses of this planet, petrological and mineralogical: though very soon we shall realize how intimate is the connection even between these and what is, in the common parlance, alive. There is a direct bridge between things inorganic and things organic and this too is part of the Wheel.
But before we start on our examination of that part of the great process which now concerns us – namely, plant and animal life and the use man makes of them – there is one further idea which we must master. It is this: The stability of Nature is secured not only by means of a very even balancing of her Wheel, by a perfect timing, so to say, of her mechanisms, but also rests on a basis of enormous reserves. Nature is never a hand-to-mouth practitioner. She is often called lavish and wasteful, and at first sight one can be bewildered and astonished at the apparent waste and extravagance which accompany the carrying on of vegetable and animal existence. Yet a more exact examination shows her working with an assured background of accumulated reserves, which are stupendous and also essential. The least depletion in these reserves induces vast changes and not until she has built them up again does she resume the particular process on which she was engaged. A realization of this principle of reserves is thus a further necessary item in a wide view of natural law. Anyone who has recovered from a serious illness, during which the human body lives partly on its own reserves, will realize how Nature afterwards deals with such situations. During the period of convalescence the patient appears to make little progress till suddenly he resumes his old-time activities. During this waiting period the reserves used up during illness are being replenished.
THE LIFE OF THE PLANT
A survey of the Wheel of Nature will best start from the rather rapid series of processes which cause what we commonly call living matter to come into active existence; that is, in fact, from the point where life most obviously, to our eyes, begins. The section of the Wheel embracing these processes is studied in physiology from the Greek word jusid, the root juw meaning to bring to life, to grow.
But how does life begin on this planet? We can only say this: that the prime agency in carrying it on is sunlight, because it is the source of energy, and that the instrument for intercepting this energy and turning it to account is the green leaf.
This wonderful little example of Nature’s invention is a battery of intricate mechanisms. Each cell in the interior of a green leaf contains minute specks of a substance called chlorophyll and it is this chlorophyll which enables the plant to grow. Growth implies a continuous supply of nourishment. Now the plants do not merely collect their food: they manufacture it before they can feed. In this they differ from animals and man, who search for what they can pass through their stomachs and alimentary systems, but cannot do more; if they are unable to find what is suitable to their natures and ready for them, they perish. A plant is, in a way, a more wonderful instrument. It is an actual food factory, making what it requires before it begins the processes of feeding and digestion. The chlorophyll in the green leaf, with its capacity for intercepting the energy of the sun, is the power unit that, so to say, runs the machine. The green leaf enables the plant to draw simple raw materials from diverse sources and to work them up into complex combinations.
Thus from the air it absorbs carbon-dioxide (a compound of two parts of oxygen to one of carbon), which is combined with more oxygen from the atmosphere and with other substance, both living and inert, drawn from the soil and from the water which permeates the soil. All these raw materials are then assimilated in the plant and made into food. They become organic compounds, i.e. compounds of carbon, classified conveniently into groups known as carbohydrates, proteins, and fats; together with an enormous volume of water (often over 90 per cent of the whole plant) and interspersed with small quantities of chemical salts which have not yet been converted into the organic phase, they make up the whole structure of the plant – root, stem, leaf, flower, and seed. This structure includes a big food reserve. The life principle, the nature of which evades us and in all probability always will, resides in the proteins looked at in the mass. These proteins carry on their work in a cellulose framework made up of cells protected by an outer integument and supported by a set of structures known as the vascular bundles, which also conduct the sap from the roots to the leaves and distribute the food manufactured there to the various centres of growth. The whole of the plant structures are kept turgid by means of water.
The green leaf, with its chlorophyll battery, is therefore a perfectly adapted agency for continuing life. It is, speaking plainly, the only agency that can do this and is unique. Its efficiency is of supreme importance. Because animals, including man, feed eventually on green vegetation, either directly or through the bodies of other animals, it is our sole final source of nutriment. There is no alternative supply. Without sunlight and the capacity of the earth’s green carpet to intercept is energy for us, our industries, our trade, and our possessions would soon be useless. It follows therefore that everything on this planet must depend on the way mankind makes use of this green carpet, in other words on its efficiency.
The green leaf does not, however, work by itself. It is only a part of the plant. It is curious how easy it is to forget that normally we see only one-half of each flowering plants, shrub, or tree: the rest is buried in the ground. Yet the dying down of the visible growth of many plants in the winter, their quick reappearance in the spring, should teach us how essential and important a portion of all vegetation lives out of our sight; it is evident that the root system, buried in the ground, also holds the life of the plant in its grasp. It is therefore not surprising to find that leaves and roots work together, forming a partnership which must be put into fresh working order each season if the plant is to live and grow.
If the function of the green leaf armed with its chlorophyll is to manufacture the food the plant needs, the purpose of the roots is to obtain the water and most of the raw materials required – the sap of the plant being the medium by which these raw materials (collected from the soil by the roots) are moved to the leaf. The work of the leaf we found to be intricate: that of the roots is not less so. What is surprising is to come upon two quite distinct ways in whch the roots set about collecting the materials which it is their business to supply to the leaf; these two methods are carried on simultaneously. We can make a very shrewd guess at the master principle which has put the second method alongside the first: it is again the principle of providing a reserve – this time of the vital proteins.
None of the materials that reach the green leaf by whatever method is food: it is only the raw stuff from which food can be manufactured. By the first method, which is the most obvious one, the root hairs search out and pass into the transpiration current of the plant dissolved substances which they find in the thin films of water spread between and around each particle of earth; this film is known as the soil solution. The substances dissolved in it include gases (mainly carbon dioxide and oxygen) and a series of other substances known as chemical salts like nitrates, compounds of potassium and phosphorus, and so forth, all obtained by the breaking down of organic matter or from the destruction of the mineral portions of the soil. In this breaking down of organic matter we see in operation the reverse of the building-up process which takes place in the leaf. Organic matter is continuously reverting to the inorganic state: it becomes mineralized: nitrates are one form of the outcome. It is the business of the root hairs to absorb these substances from the soil solution and to pass them into the sap, so that the new life-building process can start up again. In a soil in good heart the soil solution will be well supplied with these salts. Incidentally we may note that it has been the proved existence of these mineral chemical constituents in the soil which, since the time of Liebig, has focused attention on soil chemistry and has emphasized the passage of chemical food materials from soil to plant to the neglect of other considerations.
But the earth’s green carpet is not confined to its remarkable power of transforming the inert nitrates and mineral contents of the soil into an active organic phase: it is utilized by Nature to establish for itself, in addition, a direct connection, a kind of living bridge, between its own life and the living portion of the soil. This is the second method by which plants feed themselves. The importance of this process, physiological in nature and not merely chemical, cannot be over-emphasized and some description of it will now be attempted.
THE LIVING SOIL
The soil is, as a matter of fact, full of live organisms. It is essential to conceive of it as something pulsating with life, not as a dead or inert mass. There could be no great misconception than to regard the earth as dead: a handful of soil is teeming with life. The living fungi, bacteria, and protozoa, invisibly present in the soil complex, are known as the soil population. This population of millions and millions of minute existences, quite invisible to our eyes of course, pursue their own lives. They come into being, grow, work, and die: they sometimes fight each other, win victories, or perish; for they are divided into groups and families fitted to exist under all sorts of conditions. The state of a soil will change with the victories won or the losses sustained; and in one or other soil, or at one or other moment, different groups will predominate.
This lively and exciting life of the soil is the first thing that sets in motion the great Wheel of Life. Not without truth have poets and priests paid worship to “Mother Earth,” the source of our being. What poetry or religion have vaguely celebrated, science has minutely examined, and very complete descriptions now exist of the character and nature of the soil population, the various species of which have been classified, labelled, and carefully observed. It is this life which is continually being passed into the plant.
The process can actually be followed under the microscope. Some of the individuals belonging to one of the most important groups in this mixed population – the soil fungi – can be seen functioning. If we arrange a vertical darkened glass window on the side of a deep pit in an orchard, it is not difficult to see with the help of a good lens or a low-power horizontal microscope (arranged to travel up and down a vertical fixed rod) some of these soil fungi at work. They are visible in the interstices of the soil as glistening white branching threads, reminiscent of cobwebs. In Dr. Rogers’s interesting experiments on the root systems of fruit trees at East Malling Research Station, where this method of observing them was initiated and demonstrated to me, these fungous threads could be seen approaching the young apple roots in the absorbing region (just behind the advancing root tips) on which the root hairs are to be found. Dr. Rogers very kindly presented me with two excellent photographs – one showing the general arrangement of his observation chamber (Plate I), the other, taken on 6th July 1933, of a root tip (magnified by about twelve) of Lane’s Prince Albert (grafted on root stock XCI) at sixteen inches below the surface, showing abundant fungous strands running in the soil and coming into direct contact with the growing root (Plate II).
But this is only the beginning of the story. When a suitable section of one of these young apple roots, growing in fertile soil and bearing active root hairs, is examined, it will be found that these fine fungous threads actually invade the cells of the root, where they can easily be observed passing from one cell to another. But they do not remain there very long. After a time the apple roots absorb these threads. All stages of the actual digestion can be seen.
The significance of this process needs no argument. Here we have a simple arrangement on the part of Nature by which the soil material on which these fungi feed can be joined up, as it were, with the sap of the tree. These fungous threads are very rich in protein and may contain as much as 10 percent of organic nitrogen; this protein is easily digested by the ferments (enzymes) in the cells of the root; the resulting nitrogen complexes, which are readily soluble, are then passed into the sap current and so into the green leaf. An easy passage, as it were, has been provided for food material to move from soil to plant in the form of proteins and their digestion products, which latter in due course reach the green leaf. The marriage of a fertile soil and the tree it nourishes is thus arranged. Science calls these fungous threads mycelium (again from a Greek word, mukhd), and as the Greek for root is riza (rhiza, cf, rhizome), the whole process is known as the mycorrhizal association. This partnership is universal in the forest and is general throughout the vegetable kingdom. A few exceptions, however, exist which will be referred to in the next paragraph.
Among the plants in which this mycorrhizal association has hitherto not been observed are the tomato and certain cultivated members of the cabbage family, many of which possess a very diffuse root system and exceptionally elongated root hairs. Nevertheless, all these examples respond very markedly to the condition of the soil in which they are grown and if fed with dressings of humus will prosper. The question naturally arises: Exactly how does this take place? What is the alternative mechanism that replaces the absent mycorrhizal association?
A simple explanation would appear to be this. Fertile soils invariably contain a greatly enhanced bacterial population whose dead remains must be profusely scattered in the water films which bathe the compound soil particles and the root hairs of the crops themselves; these specks of dead organic matter, rich in protein, are finally mineralized into simple salts like nitrates. We have already mentioned this breaking-down process of the soil population. What is here to be noted is that it is no sudden transformation, but takes place in stages. May not, therefore, some at least of the first-formed nitrogen complexes, which result from this breaking down, be absorbed by the root hairs and so added to the sap current? That is to say that the nonmycorrhiza- forming plants, not drawing on the soil fungi, do compensate themselves by absorbing organic nitrogen in this form – they catch the bacterial soil population, as it were, before it has been reduced to an entirely inert phase and so have their link also with the biological life of the soil. That there must be some such passage of matter on a biological basis is suggested by the fact that only in fertile soil, i.e. in soils teeming with bacteria, do these non-mycorrhiza formers reveal resistance to disease and high quality in the produce, which means that only in these soils are they really properly fed.
This would be a third method used by plants for feeding themselves, a sort of half-way method between the absorption powers exercised by the root hairs and the direct digestive capacity of the roots: as the mechanism used in this method is presumably the root hairs, the diffuseness of the root system of plants of the cabbage family would be explained. It is possible that even mycorrhiza formers use this alternative passage for organic nitrogen. There seems no reason at all why this should not be so.
But how do the various agencies concerned in these intricate operations manage to carry on their work, buried as they are away from the light and thus unable to derive anything from the source of energy, the sun? How do they do their initial work at all until they can hand over to the green leaf? They derive their energy by oxidizing (i.e. burning up) the stores of organic matter in the soil. As in an ordinary fire, this process of oxidation releases energy. The oxygen needed for this slow combustion is drawn from the air, in part washed down by the rain, which dissolves it from the atmosphere in its descent. Incidentally this explains why rain is so superior as a moistening agency for plants to any form of watering from a can: incidentally, again, we can understand the need for cultivating the soil and keeping it open, sothat the drawing in of oxygen, or the respiration of the soil, can proceed and the excess carbon dioxide can be expelled into the atmosphere.
Humus is the Latin word for soil or earth. But as used by the husbandman humus nowadays does not mean just earth in general, but indicates that undecayed residue of vegetable and animal waste lying on the surface, combined with the dead bodies of these bacteria and fungi themselves when they have done their work, the whole being a highly complex and somewhat varying substance which is, so to say, the mine or store or bank from which the organisms of the soil and then, in direct succession, the plant, the tree, and thereafter the animal, draw what they need for their existence. This store is all important.
THE SIGNIFICANCE OF HUMUS
Humus is the most significant of all Nature’s reserves and as such deserves a detailed examination.
A very perfect example of the methods by which Nature makes humus and thus initiates the turning of her Wheel is afforded by the floor of the forest. Dig down idly with a stick under any forest tree: first there will be a rich, loose accumulation of litter made up of dead leaves, flowers, twigs, fragments of bark, bits of decaying wood, and so forth, passing gradually as the material becomes more tightly packed into rich, moist, sweet-smelling earth, which continues downwards for some inches and which, when disturbed, reveals many forms of tiny insect and animal life. We have been given here a glimpse of the way Nature makes humus – the source from which the trunk of the tree has drawn its resisting strength, its leaves their glittering beauty.
Throughout the year, endlessly and continuously, though faster at some seasons than at others, the wastes of the forest thus accumulate and at once undergo transformation. These wastes are of many kinds and mix as they fall; for leaf mingles with twig and stem, flower with moss, and bark with seed-coats. Moreover, vegetable mingles with animal. Let us beware of the false idea that the forest is a part of the vegetable kingdom only. Millions of animal existences are housed in it; mammals and birds are everywhere and can be seen with the naked eye. The lower forms of animal life – the invertebrates – are even more numerous. Insects, earthworms, and so forth are obvious: the microscope reveals new worlds of animal life down to simple protozoa. The excreta of these animals while living and their dead bodies constitute an important component of what lies on the forest floor; even the bodies of insects form in the mass a constituent element not without importance, so that in the end the two sources of waste are completely represented and are, above all, completely mingled. But the volume of the vegetable wastes is several times greater than that of the animal residues.
These wastes lie gently, only disturbed by wind or by the foot of a passing animal. The top layer is thus very loose; ample air circulates for several inches downwards: the conditions for the fermentation by the moulds and microbes (which feed on the litter) are, as the scientist would say, aerobic. But partly be pressure from above and partly as the result of fermentation the lower layers are forced to pack more closely and the final manufacture of humus goes on without much air: the conditions are now anaerobic. This is a succession of two modes of manufacture which we shall do well to remember, as in our practical work it has to be imitated.
This mass of accumulated wastes is acted on by the sunlight and the rain; both are dispersed and fragmented by the leaf canopy of the trees and undergrowth. The sunlight warms the litter; the rain keeps it moist. The rain does not reach the litter as a driving sheet, but is split up into small drops the impetus of whose fall is well broken. Nor does the sunlight burn without shade; it is tempered. Finally, though air circulates freely, there is perfect protection from the cooling and drying effects of strong wind.
With abundant air, warmth, and water at their disposal the fungi and bacteria, with which, as we have already noted, the soil is teeming, do their work. The fallen mixed wastes are broken up; some passes through the bodies of earthworms and insects: all is imperceptibly crumbled and changed until it decomposes into that rich mass of dark colour and earthy smell which is so characteristic of the forest floor and which holds such a wealth of potential plant nourishment.
The process that takes place in a prairie, a meadow, or a steppe is similar; perhaps slower, and the richness of the layer of humus will depend on a good many factors. One, in particular, has an obvious effect, namely, the supply of air. If, for some reason, this is cut off, the formation of humus is greatly impeded. Areas, therefore, that are partly or completely waterlogged will not form humus as the forest does: the upper portion of the soil will not have access to sufficient free oxygen, nor will there by much oxygen in the standing water. In the first case a moor will result; in the second a bog or morass will be formed. In both these the conditions are anaerobic: the organisms derive their oxygen not from the air but from the vegetable and animal residues including the proteins. In this fermentation nitrogen is always lost and the resulting low-quality humus is known as peat.
But the forest, the prairie, the moor, and the bog are not the only areas where humus formation is in progress. It is constantly going on in the most unlikely places – on exposed rock surfaces, on old walls, on the trunks and branches of trees, and indeed wherever the lower forms of plant life – algae, lichens, mosses, and liverworts – can live and then slowlybuild up a small store of humus.
Nature, in fact, conforming to that principle of reserves, does not attempt to create the higher forms of plant life until she has secured a good store of humus. Watch how the small bits of decayed vegetation fall into some crack in the rock and decompose: here is the little fern, the tiny flower, secure of its supply of food and well able to look after itself, as it thrusts its roots down into the rich pocket of nourishment. Nature adapts her flora very carefully to her varying supplies of humus. The plant above is the indicator of what the soil below is like, and a trained observer, sweeping his eye over the countryside, will be able to read it like the pages of a book and to tell without troubling to cross a valley exactly where the ground is waterlogged, where it is accumulating humus, where it is being eroded. He looks at the kind and type of plant, and infers from their species and condition the nature of the soil which they at once cover and reveal.
But we are not at the end of the mechanisms employed by Nature to get her great Wheel to revolve with smooth efficiency. The humus that lies on the surface must be distributed and made accessible to the roots of plants and especially to the absorbing portions of the roots and their tiny prolongations known as root hairs – for it is these which do the delicate work of absorption. How can this be done? Nature has, perforce, laid her accumulation on the surface of the soil. But she has no fork or spade: she cannot dig a trench and lay the food materials at the bottom where the plant root can strike down and get them. It seems an impasse, but the solution is again curiously simple and complete. Nature has her own labour force – ants, termites, and above all earthworms. These carry the humus down to the required deeper levels where the thrusting roots can have access to it. This distribution process goes on continually, varying in intensity with night and day, with wetness or dryness, heat or cold, which alternately brings the worms to the surface for fresh supplies or sends them down many feet. It is interesting to note how a little heap of leaves in the garden disappears in the course of a night or two when the earthworms are actively at work. The mechanism of humus distribution is a give and take, for where a root has died the earthworm or the termite will often follow the minute channel thus created a long way.
Actually the earthworm eats of the humus and of the soil and passes them through its body, leaving behind the casts which are really enriched earth – perfectly conditioned for the use of plants. Analyses of these casts show that they are some 40 percent richer in humus than the surface soil, but very much richer in such essential food materials as combined nitrogen, phosphate, and potash. Recent results obtained by Lunt and Jacobson of the Connecticut Experiment Station show that the casts of earthworms are five times richer in combined nitrogen, seven times richer in available phosphate, and eleven times richer in potash than the upper six inches of soil.
It is estimated that on each acre of fertile land no less than twenty-five tons of fresh worm casts are deposited each year. Besides this the dead bodies of the earthworms must make an appreciable contribution to the supply of manure. In these ways Nature in her farming has arranged that the earth itself shall be her manure factory.
As the humus is continually being created, so it is continually being used up. Not more than a certain depth accumulates on the surface, normally anything from a few inches to two or three feet. For after a time the process ceases to be additive and becomes simply continuous: the growing plants use up the product at a rate equalling the rate of manufacture – the even turning of the Wheel of Life – the perfect example of balanced manuring. A reserve, however, is at all times present, and on virgin and undisturbed land it may be very great indeed. This is an important asset in man’s husbandry; we shall later see how important.
THE IMPORTANCE OF MINERALS
Is the humus the only source from which the plant draws its nourishment? That is not so. The subsoil, i.e. that part of the soil derived from the decay of rocks, which lies below the layer of humus, also has its part to play. The subsoil is, as it were, a depository of raw material. It may be of many types, clay, sand, etc.; the geological formation will vary widely. It always includes a mineral content – potash, phosphates, and many rarer elements.
Now these minerals play an important part in the life of living things. They have to be conveyed to us in our food in an organic form, and it is from the plant, which transforms them into an organic phase and holds them thus, that we and the other animals derive them for our well-being.
How does the plant obtain them? We have seen that there is a power in the roots of all plants, even the tiniest, of absorbing them from the soil solution. But how is the soil solution itself impregnated with these substances? Mainly through the dissolving power of the soil water, which contains carbon dioxide in solution and so acts as a weak solvent. It would appear that the roots of trees, which thrust down into the subsoil, draw on the dissolved mineral wealth there stored and absorb this wealth into their structure. In tapping the lower levels of water present in the subsoil – for trees are like great pumps drawing at a deep well – they also tap the minerals dissolved therein. These minerals are then passed into all parts of the tree, including the foliage. When in the autumn the foliage decays and falls, the stored minerals, now in an organic phase, are dropped too and become available on the top layers of the soil: they become incorporated in the humus. This explains the importance of the leaf-fall in preserving the land in good heart and incidentally is one reason why gardeners love to accumulate leaf-mould. By this means they feed their vegetables, fruit, and flowers with theminerals they need.
The tree has acted as a great circulatory system, and its importance in this direction is to be stressed. The destruction of trees and forests is therefore most injurious to the land, for not only are the physical effects harmful – the anchoring roots and the sheltering leaf canopy being alike removed – but the necessary circulation of minerals is put out of action. It is at least possible that the present mineral poverty of certain tracts of the earth’s surface, e.g. on the South African veldt, is due to the destruction over wide areas and for long periods of all forest growth, both by the wasteful practices of indigenous tribes and latterly sometimes by exploiting Western interests.
Before we turn to consider the ways in which man has delved and dug into all these riches and disturbed them for his own benefit, let us sum up with one final glance at the operations of Nature. Perhaps one fact will strike us as symptomatic of what we have been reviewing, namely, the enormous care bestowed by Nature on the processes both of destruction and of storage. She is as minute and careful, as generous in her intentions, and as lavish in breaking down what she has created as she was originally in building it up. The subsoil is called upon for some of its water and minerals, the leaf has to decay and fall, the twig is snapped by the wind, the very stem of the tree must break, lie, and gradually be eaten away by minute vegetable or animal agents; these in turn die, their bodies are acted on by quite invisible fungi and bacteria; these also die, they are added to all the other wastes, and the earthworm or ant begins to carry this accumulated reserve of all earthly decay away. This accumulated reserve – humus – is the very beginning of vegetable life and therefore of animal life and of our own being. Such care, such intricate arrangements are surely worth studying, as they are the basis of all Nature’s farming and can be summed up in a phrase – the Law of Return.
We have thus seen that one of the outstanding features of Nature’s farming is the care devoted to the manufacture of humus and to the building up of a reserve. What does she do to control such things as insect, fungous, and virus diseases in plants and the various afflictions of her animal kingdom? What provision is to be found for plant protection or for checking the diseases of animals? How is the work of mycologists, entomologists, and veterinarians done by Mother Earth? Is there any special method of dealing with diseased material such as destruction by fire? For many years I have diligently searched for some answer to these questions, or for some light on these matters. My quest has produced only negative evidence. There appears to be no special natural provision for controlling pests, for the destruction of diseased material, or for protecting plants and animals against infection. All manner of pests and diseases can be found here and there in any wood or forest; the disease-infected wastes find their way into the litter and are duly converted into humus. Methods designed for the protection of plants and animals against infection do not appear to have been provided. It would seem that the provision of humus is all that Nature needs to protect her vegetation; and, nourished by the food thus grown, in due course the animals look after themselves.
In their survey of world agriculture – past and present – the various schools of agricultural science might be expected to include these operations of Nature in their teaching. But when we examine the syllabuses of these schools, we find hardly any references to this subject and nothing whatever about the great Law of Return. The great principle underlying Nature’s farming has been ignored. Nay more, it has been flouted and the cheapest method of transferring the reserves of humus (left by the prairie and the forest) to the profit and loss account of homo sapiens has been stressed instead. Surely there must be something wrong somewhere with our agricultural education.