Chapter 6
Gains and Losses in Fertility
Our discussion up to this point has turned first on the tree and then on the animal as the two great agents appointed by Nature to maintain the fertility of soils. The work done by the tree is supplemented by the smaller plants, the various types of which compete over the surface of the earth, contributing each their share to this great project. If the tree is the most important creator of fertility, the shrub, bush, plant, moss, lichen, algal film are not far behind it in efficiency.
We noted also at the outset of this book that this diversified vegetation is distributed by Nature in perfect adaptation to the different soil formations which have gradually developed out of climatic and geological conditions. The same is true of natural fauna; wild animals are distributed so as to be adapted to the regions which they have to inhabit and the conditions there prevalent. The combined result of this plant and animal distribution is that we find in Nature a wide variation, and this variation is a variation in the intensity of existence, at one point Nature causes her Wheel to revolve at a great pace, at another it slows down to an almost imperceptible motion.
The alterations which come about in climatic and geological conditions, then in soil formations, and finally in the flora and fauna adapting themselves to these changes, are slow. The forest may become the marsh, then sink and lie buried as the coal-field while other vegetation flourishes at the level of light, the bog may form the peat deposit, the river may silt up and form the bog, the mountain slope may be eroded and give way to the glade or bare pasture; but all this is done at that unhurried pace which we originally noted as characteristic of Nature's proceedings; these alterations may take centuries.
One of our major interferences with the natural round is to induce instead of these slow changes a succession of rapid transformations. Not only do we put the field where the forest once triumphed, drain the marsh and re-sow the pasture, but every three or four years, or every year, or even two and three times in the course of a year we ask the soil to grow a different crop. Now each crop adds to or takes out, usually both together in a very complex way, something affecting the constitution of the soil. In other words, we are always bringing about small intense rapid alterations of the levels of soil fertility.
We claim to know what we are doing. In reaping our harvests of barley, oats or wheat we assume that we can count what mineral and organic elements we have extracted from or added to our fields. Indeed, agricultural science now declares itself able to measure such things in exact terms, in pounds per acre of the different elements withdrawn, or alternatively is prepared to state how much of nitrogen, potash or phosphorus -- these are the three great fertilizing elements -- have been left in the fields in the form of roots, stems and straw, or are being added in the form of green crops, organic wastes and animal manures. The business of computing all this, of keeping track of the levels of fertility in our fields, is an old one, first carried out by rule-of-thumb and now the special care of the soil scientist, who advises the farmer on the points that arise. So far so good. We have here the heart of the farmer's knowledge. What eludes us are the long slow changes which in spite of all our care are apt to overtake our cultivated fields.
These long slow changes take place everywhere where man has settled and the majority of peoples have suffered from them. This expression may advisedly be used, for the changes are too often those of deterioration. If at the outset of our efforts we succeed in quickening the intensity of the natural cycle, as is undeniable when we make a natural prairie arable, drain a marsh or turn an odd bit of ground into a vegetable garden or a fruitful orchard, in fact, when we do anything at all to substitute our highly cultivated areas for natural wilderness, this seems too frequently to be followed by a slow, silent, unnoticed decline. A few nations have succeeded in maintaining, some for unknown periods and one -- the Chinese -- for forty centuries, a standard of fertility in their fields equal to the one from which they started; most nations have had to face the exhaustion of their soils.
For what we do is rather daring, and unless the utmost skill is available many mistakes lie ahead. Human history could be written in terms of success and failure in keeping abreast of this problem. If we had enough facts we should possibly be able to see how one civilization after another slowly declined with the declining energy of its peoples, inadequately sustained on deteriorating soils. Was the fall in turn of the Persian, Greek and Roman worlds due to that simple act of the devastation of forest life in the areas which were the cradles of these great races? We know most about Roman agriculture, and the story undoubtedly reads as one of the decline of agriculture, a decline of which this people was itself conscious and which its leaders and writers deplored and did their best to stem. The Roman story is tragic, for at almost any point the tide might have turned the other way. For in all this long and chequered history of the human race revival is frequent. At no point the breakdown inevitable. There is no fate or destiny hanging over humanity which bids us vanish from the face of the earth. The fullness of the earth is ours to hold if only we can learn to guard and store its treasures.
There is, therefore, no need for pessimism, which is quite misplaced in considering the facts before us. But that we need to learn some lessons may be conceded. The history of our island will form a good subject for a first analysis.
The start begins before the Roman occupation with the colonization of the south-eastern portions of the country by Belgic tribes. They brought with them the heavy mouldboard plough and were skilled farmers. They grew wheat, an exhausting crop, and exported it to Gaul. But only part of the country was cultivated, namely the lighter soils of the downlands, which were alone fit for habitation, the rest being marsh or forest. The Romans brought little change except that they introduced the villas which were large farms under single ownership run by functionaries, resembling the latifiundia of Italy against which the Roman writers rail so unavailingly. The exhaustion of the soil continued, for the demand for wheat (the staple food of the Roman soldier) was very great; in the time of the Emperor Julian no fewer than eight hundred wheat ships left for the Continent.
This organization was largely destroyed by the Anglo-Saxon invasions. The new settlers brought their own system of farming, which was above all a communal one centered in the German village from which the manor was evolved. They too used the mouldboard plough, which finally ousted the lighter Celtic scratch plough. Invented to deal with the heavy soils of the Slav countries it had made its way across Europe and was finally established in our island, where its use has continued until to-day. Its main feature is a high penetrating power, which undoubtedly enabled cultivation to be extended by slowly carving out the valleys and plains from the surrounding forest land. But its very power caused a too rapid oxidation of the available soil humus, which was not easily replaced by natural recuperation processes in a cool damp climate and which was further hampered by bad drainage and shortage of manure. Of this there was never enough, for without root crops only a few breeding animals could be wintered, while what accumulated was largely taken by the lord of the manor on customary right to enrich his own demesne.
The result was a slow and gradual exhaustion of fertility. There was not, it is true, a complete degeneration into the desert conditions such as came about in Mesopotamia and in the Roman-occupied lands of North Africa, but the harvests gradually dwindled and finally failed to suffice for the needs of the population, which was growing. For many years plagues and pestilences, accompanied by murrains among the animals, succeeded each other, leading up to the scourge of the Black Death in 1348-9 and in the succeeding years of the fourteenth century. One-third to one-half of the population perished. The very magnitude of the disaster provided a remedy, for labour became so scarce that manorial farming began to collapse and many fields had to be enclosed and laid down to grass. This gave the land a long rest; moreover, the pasturing of sheep provided considerable sources of animal manure. The soils of the country slowly recovered; fresh stores of humus were formed under the protecting grass carpet.
When increasing population led again to the breaking up of the enclosed grassland for tillage, the land was able to respond. A long period of what is called enclosure replaced the open fields of the communal system. It had the advantage that fields could be fenced (enclosed), animals thus maintained in sufficient numbers and the land in general managed on improved systems. The cultivation of clovers and introduced grasses, the bringing in of the turnip by Townshend in 1730, led later to the great improvements in livestock due to Bakewell and other pioneers. Better animals gave more manure, more manure meant richer fields. An important accompanying reform was the replanting of trees, largely following on the publication of Evelyn's Sylva in 1678. The culmination of this progress is seen in a very greatly improved system of rotations, which kept the fertility cycle infinitely more balanced; turnips were used to clean the ground and clover to trap the atmospheric nitrogen, the various stages being skilfully combined and leading up to each other in the famous Norfolk 4-course system. The Townshend reforms were popularized by Coke of Holkharn (1776-1816), who was a great landlord and a great leader.
But the enclosure movement, excellent though it was for the land, had been hard on the rural population. Many were ousted from possession, their livelihood was gone. The dispossessed formed the beginning of that huge army of general workers whose existence is in itself a factor in the situation, for such people have to be fed. Moreover, in order to buy their food they must work. Either there would have to be a starving peasant population, far too many for the land, or some other means of sustaining life had to be sought.
This means was found in industrialization. The dispossessed craftsmen of the old rural communities migrated to the towns and began to make industrial products. Then began a hunger of the cities and a hunger of the machines which put intensive pressure on farming. Many improvements were made; drainage and transport and implements were attended to. Real advances were instituted) accompanied by one retrograde step, the introduction of artificial fertilizers. On the whole, a period of great apparent prosperity for farming set in, for in spite of the sweeping away of the Corn Laws in 1846 and the free introduction of cheap wheat, there was enough demand for the other products of farming to carry the farmer along. The country was heavily stocked with beef and dairy animals.
But the great depression of 1879, which dealt such a heavy blow to British farming, showed up the weakness of the system. Two or three completely wet seasons ruined the farming world by ushering in epidemics of disease. There had already been many warning signs; the potato epidemics of 1845 and 1846, the cattle murrain of 1866 when one out of every ten head of stock perished. The returns of fertility to the land were not really sufficient to balance the demands being made on it. Since 1879 matters have become worse; a general decline of farming has set in. The outbreak of the Second World War has brought only rather desperate attempts to cash in the remaining stores of fertility accumulated under our grass carpet; for this purpose not even the most famous permanent pastures have been spared.
What then has really happened? We can rather clearly see the course events have taken. For the first half of our history we kept going at a low level of prosperity, using up too ignorantly and too fast the stores of virgin fertility recovered from the forest. The Black Death saved us, for the simple reason that it forced us to allow Nature to restore the natural grass carpet and with the grass carpet the humus content of our soils; this ushered in four or five hundred years of gradual improvement, culminating in the farming of the late eighteenth and early nineteenth century. The decline from that point was due to a faulty agriculture; more was being taken out of the soil than was being put back. In spite of some reforms this process is continuing to-day.
That our own agriculture has had this long history with its remarkable ebb and flow between conditions of soil exhaustion and soil fertility is instructive. We know the facts and can relate event to event. In spite of the many disasters which we have noted we may yet say that British agriculture has held its own in a wonderful way and its rather too low state at the moment is not necessarily permanent; it could easily lift itself again. Our island could regain all its inheritance of natural wealth.
Can we analyze any other systems of agriculture so as to throw light on this subject? The Incas of Peru are often cited, and certainly their agriculture is interesting in showing to what extraordinary perfection mankind can bring the cultivation of the earth against incredible odds. The amazing thing about the engineering feats of the Incas is that these were carried out with stone tools only. Their farming is known as staircase cultivation because they constructed stone stairways of terraced fields up the vast slopes of the Andes, tier on tier, sometimes as many as fifty in number. The construction was perfect; even to-day a knife blade cannot be inserted between the stones of the retaining walls, so accurately are they fitted together. When this construction work had been finished, coarse stones covered with clay were laid in the terraced spaces; then several feet of soil were added, which had to be brought from beyond the mountains; the small flat fields thus obtained were very slightly sloped for irrigation. The water for this purpose was brought in stone aqueducts, of which one at least ran four to five hundred miles; these may still be seen many hundreds of feet above the valleys.
Agriculture was thus successfully carried on in steep narrow valleys which might have seemed to present an almost hopeless proposition. In reality, a series of gigantic flowerpots were built, and in these was grown the food to support a nation which, as we know, reached in many respects a very high standard of civilization. Whether this agriculture had any rise or decline we cannot say; the culture of the Incas perished suddenly with the Spanish conquest. As they stand, the remains portray it perfect. They prove to what an impressive standard cultivation can be brought when there is a sufficient determination on the part of some human community to do so.
We might almost doubt the evidence of the Inca remains were they not confirmed by an existing example which seems to resemble the Inca system very closely, namely, the agriculture of the tribesmen in the Hunza valley of the Himalayas. This is equally interesting and will be referred to hereafter (see Chapter 9). But we are not restricted to these two examples, one in the distant past and the other on rather a small scale, if we want to study the best in agriculture, if we want, in other words, to study the conservation of soil fertility. The agriculture of China is still in being for us to watch after four thousand years; over this truly immense period it has kept the soils of that country at an even, and a very high, level of fertility. This is an outstanding fact. The more we reflect on it, the more remarkable it becomes. No other civilization has approached this longevity, and though we of the West may find what does not please us in some aspects of Chinese history or politics or ways of life -- usually we are more disposed to admire than to criticize -- yet when we look at the manner in which the Chinese race has managed to turn the earth's green carpet to human use while never once abstracting or despoiling the capital riches which Nature bestows on each constantly succeeding generation of men, we must admit that criticism has nothing to say and that a humble desire to learn from this people should take its place.
Chinese agriculture is outstanding in its attention to detail and above all in its old empiric wisdom. The special features of this agriculture are: the practice of mixed crop cultivations; the return of wastes to the land; the presence of the pig; the unabashed use of human nightsoil; the enormous labour spent on reconstituting the fields; the application of the principle of composting and the device of the compost heap. The result is an agriculture which is usually described as a kind of extended market gardening.
The fields are small, while the total amount of land on which a Chinese family can sustain life is incredibly limited, about one-third or one-quarter of what we require; this is possible because the agriculture is unbelievably intensive. Such agriculture shows how cultivated areas can be increased by adding to the pore space of the soil. In China not only is the ground never idle, never uncovered, but it is usual to intercultivate two or three crops together; one is being taken off the ground, one is maturing, one is coming up. Either the various drills alternate or the crops are actually mixed; mixed cereals are commonly sown (also in India); these are hand-reaped at their various stages of ripening. In vegetable growing a single plant of each sort will be put in together. It has always been supposed that plants were compensatory to each other in what they took out of the soil, but it has been left to the Chinese to draw the logical consequences from this idea, to imitate Nature's confusion as far as can be done, to plant as many different things together as can well be managed; our own practice of the rotation is clumsy by comparison. The Chinese system implies a vast amount of hand labour, but it is, at any rate, highly successful. It is carried everywhere by the Chinese settler as part of his stock-in-trade; wherever he may find himself he proceeds forthwith to mixed-crop growing.
He also keeps his garden and his fields extraordinarily tidy. Every unwanted leaf or blade of grass, every stalk and twig is collected. There is a certain putting aside of the larger stalks for fuel, which in China is cruelly scarce and a great problem. Indeed, the search for fuel inflicts some injury on Chinese agriculture by withdrawing the woody materials, but the population has to acquire some means of heating. Otherwise everything whatever of a vegetable nature, either wild herbage from the canal paths and hillsides or all the waste that comes from cultivated crops, goes back on the land.
Simultaneously with this there is always pig manure. The Chinese peasant does not contemplate farming without the pig. The pig is ubiquitous throughout the country; his flesh is eaten and his manure is the indispensable basis of farming practice. This manure is invariably supplemented by the whole of the human nightsoil. No sewage of any kind reaches the canals or streams; the Chinese never look on human excrement as something to be quietly and decently got rid of, they look upon it as a valuable substance and treat it accordingly. It has a definite commercial value. (The nightsoil of the city of Shanghai was worth $31,000 gold in 1908.)
From the wastes collected off the farm or the wayside and from the pig manure and the nightsoil is built up the compost heap; the materials of the heap, mixed, watered and worked by human labour, gradually crumble down into a rich humus which is then spread on the fields. Composting is an alternative to manuring, to which the Chinese cultivator does not often resort. (There is, however, a considerable use of dried human nightsoil not composted with vegetable wastes. This may be due to scarcity of the latter. The results are disagreeable and dangerous to health.) In our next chapter we shall have fully to explain the principles on which composting rests. Here it is sufficient to point out that the device of the compost heap is a Chinese idea, and is one of the most brilliant inventions which has ever helped man to use the riches of the earth. The compost heaps or the materials to be composted (all very neat) are seen everywhere, in the fields, in the village streets, on the canal banks. The method of composting differs, as might be expected in this huge country. The heaps do not usually run to very high temperatures (see Appendix A on this point), but a very complete breaking down is obtained, ending in a kind of pulverization. The immediate advantage of the compost heap is that it saves time and space. By building the heap upwards far less superficies are used for the creation of fertilizing material than would otherwise have to be given up; it also permits a speeding-up which is phenomenal; the two or three crops we have mentioned are possible because the Chinese cultivator is always dribbling a little compost round his plants. The fertility cycle rushes along at top speed, but as the land is always being supplied with fresh food materials it is never over-worked.
Whether in the long run the soil could hold out against this intense cropping is a moot point. A further instalment of ancient wisdom has taught the Chinese peasant not to run this risk. He has achieved the art of actually replacing his fields. It is a normal practice to dig out the rich mud from the canal and river bottoms and spread it over the land. This has to be done with spade and basket and the labour involved is colossal. But the cultivator is not deterred. The mud from below a village site is specially sought after, possibly because of the soap content (there is, as stated, no sewage content). In one part of China soil is regularly interchanged by means of hand labour between mulberry orchards and rice fields. The mulberry tree has huge roots and is thus the perfect instrument for pulling up subsoil just those elements needed for cultivation; the use of the soil from these orchards is an admirable way of restoring the mineral content of a depleted area. Altogether a colossal expenditure of labour is given to the composing and recomposing of the fields and of the soil in them, furrows and ridges being freely changed about and the soil generally moved and handled in a way which is quite foreign to our agriculture. Both men and women take part in this laborious work, which is the very sine qua non of Chinese farming. When the field has been constituted, though ploughing is shallow, the working on the soil is continued; each plant is separately cared for and soil and plant are put into perfect relation with each other.
By these practices China has avoided the exhaustion of her fertile soils. She has outlasted all the other civilizations of which we have knowledge because she has cultivated and conserved at the same time. It may be said with truth that there is no agriculture like the Chinese. Indian cultivation, beautifully carried out though it often is, does not approach the intensity of the Chinese, the compost heap being unknown; the result is a much less well-fed population. Japanese agriculture is clever and closely resembles the Chinese, but the Japanese have to wrestle with contours and natural conditions which are very different from the Chinese and which forbid the same tremendous development. The Chinese have a wonderful country, but in truth it is partly of their own making; the thousands of miles of canals, the ponds teeming with fish, the rich neat fields growing crop after crop were not given them ready-made by Nature; the materials only were supplied and close observation of natural laws, unstinted industry, unflagging patience were needed before they were welded by the labours of generation after generation into this perfect picture.
These analyses of agricultural systems have been summarized, but they will suffice to indicate two things. The first fact conveyed -- and this we owe to the Chinese, to the tribesmen of the Hunza valley and the Incas -- is that it is possible to cultivate the earth intensively and yet to maintain fertility. The second fact, which we owe to an examination of our own agricultural history, is scarcely less important; it is possible to restore lost fertility by adopting the right means and by taking sufficient trouble. The presumption is that the agriculture which can do this is more or less sound. A very faulty agriculture is a more difficult proposition, for fertility may be so completely destroyed that erosion has begun; the whole topsoil may have vanished; obviously to re-create a topsoil is no light task. But provided the topsoil is still there, however injured, it can be revived and usually with some speed.
Broadly speaking the agricultural systems of the world fall into four classes. There are the agricultures of the East, headed by the Chinese, but closely followed by the Japanese, the agriculture of Java, etc. These Eastern races have all evolved systems which may best be described as keeping the soil intact. Then comes the great agriculture of Europe, for it is great. But it is also very unequal, showing not only a remarkable variation of intensity-and this even within the single countries, with great losses arising out of poorly cultivated areas -- but also most disconcerting movements up and down; at one moment it appears to be advancing, at another, rapidly declining, and can sink very low indeed. This instability is a marked characteristic and shows that there is some inherent weakness, a weakness which exerts great influence on our mental attitude; we have no certainty in our agriculture and our discussions invariably reflect this. With European agriculture may be classed much of the agriculture in the newer parts of the world, which have drawn their populations from Europe. Thirdly come systems which scarcely merit the name of agriculture. They are sheer exploitations and are usually described as mining the land. We have already mentioned this topic and need not dwell on it. There are many forms of it, nor is this robbery to be imputed to any one nation, one period or one interest; we have all alike contributed something. Finally, there are forms of primitive agriculture. There is still a great deal of this in the world. It is difficult to classify, often conserving fertility though on rather a low level, but almost as often destroying it by wasteful systems of shifting cultivation.
It will be well to concentrate on what we have called the European system, because this is our special concern. Some further aspects of Eastern agriculture will be considered in our final chapter. We noted how apt European agriculture was to advance and recede, and how it varied within itself. There must be a range of soil fertility in Europe embracing almost every degree of good and bad. When one area or country seems to be rapidly on the downgrade, some effort is made, some fresh idea is brought forward and progress at once takes place; fertility is either restored or notably advanced. The recent opening up of the Campagna is a good example. At first an important food-producing area it then lay derelict for centuries; a few years sufficed to restore it to all its old capacity and probably much more. The same thing was done with our Lincolnshire fens under the Stuarts. There are innumerable examples of such projects, which are almost always successful; it is rare to find a failure. This shows that the inherent fertility of the European soils is still in being; it also shows that we are capable of making it available. But what perhaps is really more significant than these large-scale projects are the day to day small improvements being carried out on every well-run farm or estate in our continent. A marsh drained here, a water-course controlled there, an avenue planted, a field contoured, a vineyard terraced. The efforts thus put forth by farmer after farmer or owner after owner amount in the aggregate to one colossal determination to maintain, conserve and, if possible increase fertility; to these efforts the soil responds.
Why have the soils of Europe the capacity both to lose and to recover so remarkably under human cultivation? The answer lies partly in natural conditions and partly in ourselves. Partly in ourselves, because in spite of much carelessness and neglect and many errors we have managed through the long course of our history to keep the plant and the animal in some sort of relation to each other. Our European agriculture is based on mixed farming, a term which has already been explained (see Chapter 5). In doing this it follows one of the most important of all natural laws, one which is the very basis of the fertility of soils. We shall have a great deal of criticism to direct later against our ways of managing the use, of the waste products we get from our animals, but to have kept this animal population for two thousand years and to have distributed it throughout the whole area in proportions well adapted to the varying conditions has been our triumph.
It has been a mixed animal population, and this also has been to the good. In grazing, for instance, different animals take different parts of the grass for their food. Their mouth and lip formations are not the same, and they graze more or less closely. They also have varying preferences and dislikes; some animals cannot be got to touch coarse grass, others will eagerly clean it up. The way they graze will affect the way their dung and urine come to be distributed over the field. (A good popular account of the problems of grazing will be found in Michael Graham: Soil and Sense, Chapter 8, "The Animals".) The art of the grazier consists in allowing the various animals to enter and roam the field in such a way as to insure that they take what they want not only without damaging the herbage but so as to maintain and, if possible, improve the grass. The skill displayed in doing this can be the study of a lifetime. Success can only come with knowledge and experience, but there is also a kind of flair or instinct for getting the best results which distinguishes the good grazier. What is interesting is the conscious recognition of the fact that the grass and the animals are one project and the care taken to manage the various stages of growth or consumption of the sward in relation to the different types of animal to be maintained. In the management of grassland the English farmer stands pre-eminent, but it may in general be said that the relation of the animal to the soil is well understood throughout Europe. This has greatly helped to conserve fertility. Unless for some reason the animal population sinks very low, there is in the soil a reserve of animal enrichment which can always be called upon.
But we have also been greatly favoured by natural conditions. Because our continent lies in a temperate zone with plenty of moisture it has a natural grass cover. Though it is true that the tree would oust the grass if it were allowed to, yet the grass has a tremendous strength of its own. We are so accustomed to see grass spring up everywhere that we scarcely pay attention to this; yet it is a most important fact.
What does grass do to the soil? The answer can be given in three words. Grass protects soil. It protects soil from wind, sun, rain and all the forces of Nature, from burning, drifting, flooding. If the humus of the topsoil has been called the skin of our planet, the grass is like a skin to a skin. We might even press this analogy further; as the animal breathes, exudes and drinks through its skin, so does the topsoil breathe, exude and drink through the grass. And, like skin, the grass with rough usage can become tough, hardened, and almost, as it were, leathery.
The protection afforded by the natural grass cover in temperate climates can hardly be exaggerated. It has been calculated that soil without a grass cover wears out more than four times as quickly as soil protected by grass; some estimates put the contrast in rates fantastically higher. Such calculations may be speculative, but it cannot be denied that soil without grass is exposed to risk whereas soil under grass is safe. It is anchored, it is kept aerated, it is pulverized by the fine combing action of the grass roots; above all it is kept both moistened and sweet, and it is also fertilized because it is constantly using the sunlight to build up a supply of vegetable wastes.
Grass keeps soil moist and sweet in a very simple way. In a forest the rainfall seeps right through the ground to a considerable depth and in doing so carries with it the dissolved calclum carbonate and soil salts; the forest humus is therefore apt to be acid. In a desert, on the other hand, the hot surface actually draws what water there is in the soil to the top, where evaporation takes place, sometimes leaving the salts which accumlate; the sand of many deserts, therefore, is apt to be alkaline, sometimes excessively so. But in the land under grass there is a balance. The movement of water is equalized; there is an excess neither of percolation nor evaporation. Soil under grass is thus kept both moist and sweet, and useful natural clovers and vetches readily root in it. These plants have themselves a capacity for fertilizing the soil, but in general the whole of the grass cover adds to the soil's enrichment. For the grass is constantly growing, i.e. it is constantly using the energy of sunlight to collect inert elements and convert them into the organic phase; as it dies, all this mass of organic matter is added to the soil. Now this does not happen at intervals; it is going on all the time. A sward is a permanent fertility instrument, hence its importance.
More especially do the roots of the grass as they die form a thick mass of decaying organic enrichment, perfectly adapted to evoke the action of the soil bacteria and of the humbler species of soil fauna. The result is an abundant, teeming life in the top layers of any soil under a grass cover. Provided only that there is adequate air this life can be counted on to continue and to add month by month to the wealth of the soil. It is true that if the air is cut off this life dies down. This can happen when the grass gets old. Adequate aeration of the grass, therefore, is important; otherwise the result is a poor pasture in a sour condition.
These facts are now so well understood that a whole system of farming has arisen based on them. The point of departure is the fertility which the grass, acting as Nature's instrument, has collected; the aim is to catch this fertility at intervals and turn it to account. Land is kept under grass for three, four or five years, then ploughed up and used for cropping; the crop benefits by the fertility which the grass has collected. This can be done again and again. Such a system is known as ley farming, from ley, the old English word for a temporary grass field. The system is being much advocated at the present day (under the leadership of Sir George Stapledon and the staff of the Experimental Station, Aberystwyth).
It can be carried further and old permanent pastures can be ploughed up. But here we are faced with a dilemma. Either these permanent pastures have been properly handled, above all properly aerated and limed, in which case they are really too valuable to be so sacrificed, for they have been the work of years; or they have been neglected, have become sour, as we saw above, and pot-bound, in which case the fertility we gain by cashing in on them is not great. It would be better to improve such poor pasture and make the grass cover do its work properly before any attempt is made to turn it to further use. Grassland is so valuable, taken as the basis of an animal industry, that it requires to be treated with the utmost respect.
We may perhaps now pause for a moment to review the information which we have acquired on this subject of soil fertility and its gains and losses. We know that the tree is one great contributor to that fertility; it pulls up the valuable and needed minerals from the subsoil. We know that the animal is equally necessary; it is a donor of wastes. In the third place, we have realized what a useful agency we have in a grass sward, calculated as it is to keep the soil in good condition and to augment its content of organic matter; this, we have lately come to understand, can be easily brought about, that is to say, the process can be emphasized and accelerated, by ploughing up the grass and allowing it to decay rapidly in contact with abundant air and moisture.
This operation, apparently so simple, involves a great deal. We shall have to grasp a little more nearly what these questions of soil fertility imply. We have spoken of soil fertility in a broad way, but such fertility is the end result of movements and relationships which are among the most complicated in Nature; anything we attempt to enhance it is inevitably an intrusion into these relationships. This need not deter us as long as we never forget that they are still proceeding, as long as we remember that the soil is alive.
Much of this life of the soil depends on the circulation of nitrogen, which is the outstanding movement among many. This circulation is very wide, embracing the atmosphere and the plant as well as the soil. Plant, soil, and atmosphere are like cogwheels fitting into each other, supplying and exhausting the nitrogen in never-ending alternate motion. The movement is not always at the same rate; it is periodic, with the result that the accumulations of combined nitrogen in the soil follow marked phases, and these again differ according to place and climatic circumstances. The cultivator's aim must be to study this so-called nitrogen cycle very carefully in his own locality and to take the fullest advantage of it on behalf of his crops.
He has further to remember that the amount of combined nitrogen in the soil is in relation to the amount of carbon. The relation is 10 of carbon to 1 of nitrogen and is known as the carbon-nitrogen relation. It is the desire of Nature to keep this relation stable, and should it alter she at once sets to work to restore it. This means that any additions to the soil of organic matter (containing carbon) or of nitrogenous manures set up a whole series of fresh movements among the microflora, to whom is assigned the task of keeping the soil in condition.
With these facts in our mind it will easily be seen that the art of adding to the fertility of soils is not likely to be an easy one. From time to time in the history of agriculture new devices are tried, such as the device of ley farming just described. Ley farming is really only a special form of green-manuring, which has been known for a very long time as a means of increasing soil fertility. It is an old practice to dig in weeds and many nations, including those in the East, follow some form of green-manuring. A green-manure crop is one grown for consumption not by animals or man, but by the soil organisms; when the time comes to reap it, it is not carted away and harvested, but dug or ploughed in on the spot; the soil then digests it and anything it contains must augment soil fertility; the following crop profits. Green-manuring thus implies making a very special use of the green plant's capacity to collect and work up raw materials.
The results of green-manuring have been unequal and have caused much disappointment; the succeeding crop does not always prosper. The reasons are not difficult to understand. Green-manuring is based on the theory that any accumulation of nitrates in the soil must either be used or banked; if this is not done, they are in danger of leaching away by the action of the rain-water. The interposing of a green-manure crop is a form of banking; such a crop acts as a kind of savings account for the available combined nitrogen, which can later be released for the use of other plants. Success depends on a very accurate knowledge of the phases of the local nitrogen cycle, for unless the green-manure crop is interposed exactly at the right time, when there is an accumulation of combined nitrogen, it is more likely to exhaust the soil than to enrich it. A green-crop is a living crop and will act like all other living organisms; if its food materials are not ready to hand, it will look everywhere for them, in other words, it will comb the soil for any combined nitrogen it can find. The banking process can obviously only be carried out when there is something to bank, and any attempt to introduce it at the wrong moment naturally results in locking up the current account in a very disastrous way.
Another point which has to be realized is that the green-manure plant is at different stages according to age. When young it banks a great deal of nitrogen; when old, less nitrogen and more organic matter. If ploughed in young the material decays quickly, if ploughed in old much more slowly. Indeed, the amount of organic matter may then so far outweigh the available nitrogen that the soil organisms which have to carry out the decay have to call on some of the already existing soil nitrates to enable them to accomplish their work and get the carbon-nitrogen relation in the soil into balance again. When this happens it will easily be seen that the green-manure itself and the growing crop which is supposed to be profiting by it may be actual rivals for what combined nitrogen there is, so that instead of profiting by the green-manure the crop is starved of nitrogen. This accounts for many of the disappointments following on the use of a green-manure. When ploughing in such a crop the addition at the same time of a little animal manure or compost -- these will contain nitrates -- is by nature of a safety device to insure against such depredations of the existing soil nitrogen; it will be found that the green-manure crop then decays far more rapidly, for the organic matter which it includes has a sufficient supply of nitrogen assured to it; in this way an ample addition of all the elements that make for fertility is added to the soil in natural proportions.
It was supposed to be a very great improvement on ordinary green-manuring when it was discovered in the 1880's by Schulz-Lupitz that certain green-manures could be made to collect their own nitrogen; this nitrogen was the free nitrogen of the atmosphere. As we know, a certain group of plants, like the pea and the bean, bear on their roots, sometimes on their stems, small visible buttons, termed nodules; in these nodules are great colonies of microorganisms known as Bacillus radicicola, which have the unusual property of being able to fix, i.e. absorb the free nitrogen direct from the air and turn it into the combined form when the pea or bean haulm is dug in; this additional supply of combined nitrogen helps to increase soil fertility. The principle is again a sound one, but too much stress has been laid on it. The original experiments were made on very poor sandy soil in North Germany, and wherever comparable conditions obtain the results will be similar. But the work of the nodule-bearing plant is only one mechanism among several for transferring the free nitrogen of the atmosphere into the combined form in the soil. The eagerness with which the modern farmer has recourse to the help of such plants is largely due to the general running down of our European soils, which has rendered some means of restoring their nitrogen content essential.
The nodule-bearing plants are by no means so unique as they may seem. There are other agencies doing similar work. Indeed, soil which is really fertile will largely look after itself. This is well known to the best cultivators, those not caught by the prevailing idea that soil must always be whipped up for production; such cultivators will speak of making the land manure itself. In speaking thus they are relying on natural means of intensifying the nitrogen cycle, means which when once set into good motion will be almost automatic. For the soil is in no sense defenceless; it holds within itself or on its surface a sufficiency of the instruments likely to maintain its life at an appropriate level. It is true that if we wish greatly to intensify our cropping we have to do something to add to the fertility of our soils; these additions will themselves have to be of a type and kind to fit into the natural evolution of the soil; that is what is meant by manuring. But the intensification which we can thus procure is, as it were, only an extra story to a building which has been slowly constructed from the foundations upward and which awaited us already complete when we undertook our improvements. In fact, our most ingenious operations are but trifling additions to Nature's own sound management of her soils.
Our information on this point will probably be extended some day. It was only fifty years ago that we first obtained knowledge of the existence in the soil of large colonies of bacteria, which have been named Azotobacter, capable of fixing the free nitrogen of the atmosphere. These colonies are independent of the life of plants -- the technical term is free-living; several species are known and they are specialized for different climates. To their activities a great deal of importance may be attributed. Like all other inhabitants of the soil they are very sensitive to the conditions in which they live; it seems certain that only a sweet fertile soil offers them a good home. The result is obvious. A soil in really good heart will continue to keep up its supply of combined nitrogen owing to their presence: a poor soil which has to work without them will remain poor -- a singular illustration of the law that to the rich much will be given.
This is the explanation of much soil management, including grassland management. It is a fact known to every grazier that with a reasonable amount of care a good pasture will remain in condition for years. Many of our best pastures have long histories; they are the product of slow building up, but when once constituted they are stable and most valuable, which is one incidental reason against sacrificing them for any temporary ploughing-up campaign. They do, in fact, largely manure themselves, and they must do so partly by the presence of natural nodule-bearing plants like wild white clover but largely also with the help of the Azotobacter which they carry. Probably the best demonstration on these points was that made about a generation ago by one of our greatest agricultural leaders, whose ideas have recently attracted renewed attention. Elliot, the inventor of what is known as the Clifton Park system of farming, a system which has led to our modern ley farming practice, on acquiring some worn-out-grasslands in Roxburghshire in Scotland, set himself to reconstitute them. He ended his life by declaring that in his opinion these worn-out lands, which had been cropped for sixty and seventy years and never manured, could be made to produce grass as good or even better than they ever had. This was a definite effort to restore fertility which bad been lost, and in the absence of heavy manuring the only source from which the needed combined nitrogen can have been acquired must have been very gradually from the free nitrogen of the air by the action of Azotobacter.
What is significant is that the man who made this effort and was so sure of his opinion had been a coffee planter in Mysore and had already used his powers of observation in dealing with Eastern agriculture. He records an example of the way' the fertility problem was managed in that State in the growing of cereals; this example is striking because cereals are an exhausting crop. Six drills of cereals were sown and a seventh of beans, a nodule-forming plant. After the cereals had been reaped the spaces occupied by the six drills were ploughed up and the beans allowed to cover the ground and spread; the beans were then reaped. The only manure given was the stalks of the beans and a scanty supply of ashes from cow dung burnt as fuel. The nitrogen can only have been restored, partly by the nitrogen-fixing capacity of the bean nodules, partly by the similar capacity of the soil Azotobacter. This system had continued for many centuries. (R H. Elliot: The Clifton Park System of Farming, ed. Faber & Faber, p. 226 and p. 242.)
An even more significant example was recently found in North Africa. At Tafrata in Morocco pockets of land have been formed in the rifts of the desert floor. The depth of soil is twenty-five feet or more, the fertility inexhaustible. On this land lucerne is grown under irrigation and not less than sixteen cuttings are possible in the year. No animal manure is given, yet the manurial cycle does not fail. The observed fact was that there were no nodules on the roots of the lucerne, so that it cannot have been through these that the restoration of the combined soil nitrogen was made. It can only have been due to soil Azotobacter.
The ideas suggested in the above examples, taken at random, show an almost unsuspected capacity in soils to supply their own needs. There is always ample free nitrogen in the air; our problem has been to convey it as combined nitrogen to the plant. Hitherto we have trusted to manuring to keep up the soil content. It is possible we have been overlooking more direct ways of securing the same end, which play a much larger part in Nature than that with which we have been crediting them.
Nor have we even now finished our survey of what the soil can do for itself. One of the greatest puzzles of agriculture is the growing of rice. Not only is rice the largest crop in the world, feeding the most people, but it is also one of the most ancient; incidentally it is one of the healthiest -- very little disease is found. The strange thing is-and this is a fact too little regarded by the Western scientist -- that rice after the seedling stage is hardly ever manured. It is grown in the same paddy field year after year and this has been going on for centuries. That is an anomaly according to our ideas; we should have supposed nothing could be more exhausting to the soil. It is true that the seedling is highly manured; this makes it strong and resistant, for the earliest stages of plant life are like the earliest stages of animal life -- if the young organism is well fed it can later withstand much. But after being transplanted the rice plant has to draw all its nourishment from the muddy bottom of the paddy field, which never receives much enrichment, and has so continued for centuries.
The explanation must be that these fields have manured themselves. By some means they must have restored their own nitrogen content; otherwise growth could not conceivably continue. It is a legitimate supposition that the rich algal film which always occurs in the paddy water long before the rice harvest is the nitrogen-catching agency; like the Azotobacter the algae have this capacity for nitrogen absorption. The nitrogen they trap is presumably added to the soil each succeeding season. The algal film, the action of which must be intense, is a good deal more marked in tropical zones than in our own. Here then we have a perfect example of fields which manure themselves. The scale on which this happens and the uninterrupted continuity of the process are instructive lessons in the possibilities within the reach of mankind.
The gains and losses in soil fertility following on man's opening up of the earth's surface is a study which can convey many lessons and some warnings. One likelihood which emerges is the risk of a long slow soil deterioration. In view of the demands we put on the land, of what we expect our plantations, fields, orchards, and gardens to do for us, this is not surprising. The strength of our soils is nevertheless so great that deterioration is almost imperceptible; no one generation of men and women is immediately conscious of what is happening; the earth seems always to give forth, the green carpet renews itself.
Nor is this gradual deterioration imperative; it is not a law of Nature. It can be prevented. It is worth while to contrast the history of different agricultures and different civilizations. One or two nations have solved the problem of maintaining fertility; one of the greatest crops in the world has been grown for centuries without detriment to the soil; the densest population to be found anywhere continues to subsist and to carry on a famous art and culture without injury to Mother Earth. When it comes to our own problem we find ourselves in possession of a great natural asset -- our grasslands. How are these to be treated? Two facts emerge. First, that the animal and the grass it eats are one project and together contribute to the wealth of the soil; second, that the grass and the soil are also one project; if the soil renders the grass thick and good, the grass in its turn enriches the soil. In fact all is geared together, the gases of the air included.
That is why it is so necessary never to relax our hold on soil fertility, because here the start is made and from this base everything is affected. We shall do well, therefore, to study the origin of soil fertility, to trace it to its actual beginning, to describe that section in the Wheel of Life where it first emerges, in fact, to follow the turning of the Wheel to its lowest revolution. In doing this, we shall find that we have again to take up the lesson of the East.
Next: 7. The Lowest Revolution of the Wheel
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