11. Coals to Newcastle
THE problems connected with soil fertility are now very grave, yet future writers may find them not serious, but perhaps even amusing. Nevertheless, our present serious attitude toward these problems is fully justified, for too many American farmers, as well as their colleagues abroad, are at death grips with the economic problems arising from the mismanagement of the soil. However, when the existing unbalance has been adjusted and we are able to look back upon the scarcely excusable follies of a pseudo-scientific agriculture, it will afford us some satisfaction that, despite man's struggle for generations against odds of his own creation, he at last discovered the truth. We have been becalmed agriculturally, like the famous shipwrecked sailors -- thirsty for days as they floated in the mouth of the Amazon.
Plenty of plant food is available in our soils. There is absolutely no need for commercial fertilizers. Nature can make available annually enough new plant food to grow crops several times as large as we produce now. Our present era of decreasing crops can be explained only by the fact that by ploughing we beat into unproductive submission soils which, when not disturbed by man, produce a vigorous growth continually. We have known for a long time that the "upper six inches" of soil contain enough of the least abundant plant food elements to produce maximum crops for some four hundred years. How much greater quantity must be held in the successive underlying layers between here and China! There are infinite possibilities for high production by these soils that we have worn down. Modern man has not visualized the high yields that will spring from the soil just as soon as nature receives full co-operation.
In the past, we have believed that we were co-operating with nature, but we have not made use even of well-known facts that most high-school science students grasp early in their careers. Until we begin to put these principles to work, we can scarcely be said to co-operate with nature. Instead, we have been working at cross purposes with the design for growth through which all plants exist. It is as if we tried to feed fish in an aquarium by scattering food on the plate-glass cover.
Thirty years ago students of soils at the University of Kentucky asked why it is necessary to apply fertilizers to soil richly endowed with the very elements that fertilizers contain. The answer given was that the minerals of the soil are highly insoluble, otherwise they would not be in it. This sounded logical. We could understand that, if only one-fourth of one per cent of the relatively small quantity of phosphorus in the soil could he dissolved each season, crops might easily suffer, even though ample phosphorus existed in the soil. Thus we were satisfied by explanations which seemed reasonable, but which did not take into account the inconsistent thriftiness of the natural landscape.
Everywhere about us is evidence that the undisturbed surface of the earth produces a healthier growth than that portion now being farmed. Barring setbacks such as forest fires, trees in a woodland become sturdier every year, and each tree also adds a new ring of wood beneath its bark. The minerals of the earth evidently are available in abundance to these trees -- more each succeeding season, despite the heavy tax of wood growth, the foraging by wild animals, and the other tolls which, all together, must equal or surpass the drain on plant food from cultivated land.
Innumerable buffalo, wild horses, wild cattle, goats, deer, and other animals fed upon the grasses of the plains. Millions of these animals were nourished by the vegetation on the untilled prairie land. In supplying food for this multitude, the underlying soil, through the use of the "insoluble minerals," developed a growth of grass which in many places would hide a rider on horseback. All this came without the help of man. No artificial fertilizer was applied; no ploughing was done; no cultivation was undertaken -- there was nothing whatever of the "advantageous" contributions man makes toward plant growth; yet on these plains was found the most amazing development of nutritious grasses the world has ever seen. We may well wonder just what help man does contribute.
We can recognize the fact that man at his best contributes nothing to the growth of plants; at his worst he rapidly destroys excellent growing conditions, under the delusion that he is nurturing his crops. Millions of farmers contribute to the soil food materials in the form of fertilizers and manures; but in their handling of the land they force the loss from the ploughsole of many times as much as they contribute; so that the net effect of their well-meaning work is to deprive their crops of the sustenance which nature so generously provides for all plant growth. The net effect of fertilizing the land, then, is not to increase the possible crop yield, but to decrease the devastating effects of ploughing.
The manner in which ploughing robs crops of their rightful decomposition products has been demonstrated in previous chapters. Now it is time to show how the land, if left to itself, is capable of far better production than farmers ever get from it. By analyzing the physical, chemical, and biological conditions created by ploughing in the subsurface, we are able to determine definitely just why the farmer has never been able to equal the natural landscape on land that had been allowed to deteriorate to any degree. This discussion is somewhat technical, but it is necessary for an understanding of the problem.
Conditions which favour decay are the same as those which favour the growth and development of those bacteria which are the agencies of decay. We know, of course, that nearly all decay bacteria are most active within a certain temperature range, with a certain degree of moisture, in the presence of a suitable food supply, and (depending upon the kind of bacteria) with either an abundance of air or a restricted supply of air. We know, too, that it would be difficult to imagine conditions better suited to encourage decay than are usually provided just under the surface of the soil. By ploughing, the farmer places the decayable organic matter in the most favourable environment for prompt and complete decay. The organic matter itself is the food. The bacteria are always present in Nature. During much of the year moisture and temperature conditions are within what bacteriologists call the optimum range. It is not surprising, then, that whatever the farmer ploughs into the ground cannot be recognized a few weeks or months later. It has simply vanished through decay.
All decaying matter produces carbon dioxide, a gas which is heavier than air. The air in a well is displaced by it if something is decaying in the water. Carbon dioxide accumulates in the empty part of a half-filled silo. Many men have died in wells and silos because they did not know that this lethal gas lay below the air at the top. The smoke from a fire is chiefly carbon dioxide, but the heat of the fire provides the force necessary to lift it. In the absence of such a force, carbon dioxide accumulates under the air, forcing the air upward. Ploughed-in organic matter, if in sufficient quantity, creates a zone of decay which is rather continuous and at approximately uniform depth. This decaying mass constantly releases carbon dioxide while decay is in progress. The carbon dioxide must fill the soil, gradually and completely forcing out the air which occupied the spaces between soil particles. There is no alternative, because there is no force, such as the heat of a fire, to remove the carbon dioxide generated at the ploughsole.
That decaying organic matter must completely fill the soil with carbon dioxide has never been thought of as significant. Indeed, so insignificant has it seemed that the fact has never been emphasized in courses in soils. My test work in the field in 1940 showed conclusively that something important has been overlooked in this connection. There was irrefutable proof that my crops obtained their nitrogen almost solely from the atmosphere. This would not have seemed odd if the crops had all been legume crops, for the legumes have long been known to use nitrogen obtained from the air by the nitrogen gathering bacteria that become parasitic on their roots. However, the only legumes I had were green beans. My other crops were tomatoes, cucumbers, onions, potatoes, cabbage, and lettuce. All these crops, legumes or others, thrived equally well, although no nitrogen was used anywhere on the farm in that year. Moreover, the land was not capable of providing more than a small fraction of the nitrogen used, and the only organic matter supplied was the tall rye that was disced in. It is a well-known fact among scientific men that, if rye from three to six feet tall is ploughed in, several weeks must elapse before it is safe to start crops in the land. Also, it is well known that, for rapid decomposition of such a mass of material ploughed in, it is necessary to put in with it a generous application of nitrogen fertilizer. None of these requirements was met on my farm; yet every crop had all the nitrogen it needed throughout the growing season. Thus there was plenty of evidence that these non-leguminous crops had access to atmospheric nitrogen as completely as legumes produced under the most favourable conditions. Obviously, some unusual condition prevailed to make this true.
The only unusual condition was that all decomposition occurred in circumstances which provided an abundance of nitrogen continually to saprophitic nitrogen-gathering bacteria (which require no living host to provide them with the needed carbohydrates to supplement the nitrogen they get from the air). Since 1901 it has been known that such bacteria exist in the soil. Their ability to gather nitrogen under laboratory conditions has been proved conclusively in many labouratories, but these findings have gathered dust on the shelves because nobody had ever thought to force these bacteria to "eat"" organic matter in the open air. When decay occurred at the ploughsole, nitrogen as a component of the air was excluded; therefore, these saprophytic nitrogen gatherers were denied their atmospheric nitrogen. It appears from my field tests that if the rotting of the organic matter occurs in the open air, these bacteria are just as efficient at gathering nitrogen as are their parasitic kin. Moreover, the nitrogen gathered has no chance to be lost; for the crop roots are present to make use of it as soon as the bacteria die and become part of the decaying mass. The crop plants get their nitrogen almost directly from the air.
This discovery means that hereafter no one needs to buy nitrogen as a fertilizer. It means also that no one needs to grow legumes in order to have the benefit of the nitrogen they accumulate in the soil. Furthermore, since lime is used on the land solely because it creates better conditions for growing legumes, there will no longer be a necessity for farmers to buy and apply lime to their soil. One small discovery, then, makes possible the discontinuing of a considerable expense in farming. Nobody is going to buy lime or nitrogen fertilizer, or grow and plough down legumes, when crops can obtain their own nitrogen from the air without this bother and expense.
This, however, is not the entire story. Crops cannot live on nitrogen alone. They must have in relatively small quantities many minerals which can be obtained only from the soil. The decay of organic matter plays an important part in releasing these minerals from the relatively insoluble crystals that have resisted weather influences since time began. Organic matter itself contains some of the minerals, which, as it decays, are released for the use of neighbouring plants. In the process of decay carbon dioxide gas is released; and when it dissolves in water, carbonic acid results. Thus water and carbon dioxide together are carbonic acid, the best known natural solvent for plant-food minerals. Carbonic acid readily reduces to carbonates, or other usable forms, those minerals which in the presence of water alone dissolve very slowly.
When organic materials decay at plough depth, the water below the ploughsole is prevented from moving into the upper layers of the soil. (This is especially true if the quantity of organic material is so great that it separates completely the subsoil from the topsoil.) As a result, the land quickly becomes dry and remains dry throughout the period of decomposition. Because the soil into which the carbon dioxide is discharged is dry, no carbonic acid is formed, and the gas eventually escapes from the mass of minerals without having contributed to the release of mineral plant foods.
In disced soil the situation is quite different. Water from deep in the earth can rise to the soil surface, or until it is caught and absorbed into organic matter. Because the movement of water in the whole mass of soil is unrestricted, there is always water present (at any time when decay is possible) to dissolve the carbon dioxide gas given off by the decay. No carbon dioxide escapes from the soil, and most of it becomes carbonic acid. This acid releases for the use of adjacent plants the otherwise adamant minerals which are so badly needed by farm crops. By this simple and well-known chemical action in the soil, the organic matter itself goes a long way toward providing the minerals which otherwise the farmer must buy in a bag.
Can decaying organic matter in the surface of the soil release enough minerals for maximum crops? The answer seems to depend altogether upon how much organic decay is in process during the growing season. I cannot state whether maximum crops can be expected from land into which great quantities of organic matter have been disced -- without the application of artificial fertilizers. I feel sure, however, that very early in the process of rejuvenating soil by restoring organic matter to its surface, farmers will discover that no application of fertilizer, however great, results in an increased crop yield. This opinion is based solely upon experiences and observations during strictly unofficial tests. It seems entirely reasonable to expect that the quantity of minerals released during any growing season wil be sufficient to produce maximum crops, providing the volume of carbonic acid formed by decay is adequate.
It may be suggested that -- judging from experience, again -- what we now think of as maximum crops will be badly dwarfed by the actual results that will follow the discing of important quantities of organic matter. I have already produced crops in excess of one thousand bushels per acre under such conditions as I am describing, without fertilizers or any soil amendment other than plenty of organic matter.
When farmers and scientific men begin to experiment with this plan for the growing of crops, they will be surprised and disappointed at the appearance of the plants during a considerable portion of the growing season. Crops that are destined to produce two or three times the customary yield will look as if they could scarcely produce an average yield. The colour, during dry, windy weather especially, will not be the dark, lush green that we have been accustomed to associate with healthy crops. Even in moist, favourable periods crops grown without the use of nitrogen fertilizers will be quite ordinary in appearance. Many a farmer, when he observes this absence of dark green colour, will want to crowd the crop by the use of nitrogen fertilizer. However, if he is wise, he will wait patiently to see what the outcome will be without nitrogen. That outcome will please him beyond measure, considering that all his past experience will have taught him to expect a short crop. When he discovers a big increase in yield, he will be entitled not only to wonder why, but to analyze his results.
The explanation of this strange phenomenon is simple. For as long as most men now living can remember, fertilizers have carried some nitrogen. The nitrogen in early fertilizers designed for staple crops was usually not more than 2 per cent -- forty pounds to a ton. At the usual rate of application of fertilizer, at most two hundred to three hundred pounds per acre, this small application of nitrogen, four to six pounds per acre, could do nothing more than "advertise" the fertilizer by keeping the crop dark green until hot weather came. Then, the rapid loss of colour would be charged against drought or some other circumstance. We may conclude, then, that our judgment of a healthy green colour has been warped by our fertilizer experience.
Experienced farmers and scientists know that if a crop grows too luxuriantly in the early weeks, when there is plenty of water, it is likely before harvest time to encounter weather conditions which will make such growth difficult to maintain. Such events precede the firing of corn blades. Often, when the farmer has overdone nitrogen feeding at planting time, the rainfall will be sufficient for a few weeks to induce extraordinary growth. The almost inevitable sequel is dry weather, which suddenly stops the liberal flow of nutrients into the plant. Retrenchment in the form of dead leaves -- so that the available nutrients can support the remainder of the plant -- is a forced procedure. Fired corn blades, therefore, are no mystery, but should be expected as a result of certain fertilizer practices.
There is plenty of nitrogen in the air; there are practically unlimited quantities of mineral nutrients in the soil The new practices make it possible to utilize natural forces to make these available. Therefore, we should hereafter stop carrying coals to Newcastle, by fertilizing soils that already have an abundance of plant food.
12. Exit Pests
THE hypothesis that environment influences plant disease and insect damage is not new. In early agricultural literature, writers generally accepted the theory that the better the growing conditions for plants, the less the risks from disease and insects. From 1910 to the present time, however, it has been difficult to find this theory expressed in writings on agricultural subjects.
It is true that the era of soil depletion has been contemporaneous with the period in which diseases and insects have become most troublesome. This could be true, of course, without being significant; but there are very good reasons for supposing a connection to exist. Many farmers can remember when there were no colorado potato beetles, San Jose scale, and other insects and blights now common. These same men can remember also that at that time their ploughs separated a zone of almost black upper soil from the yellowish subsoil. This black topsoil has now disappeared; at the same time many new insects have made their appearance, and those that were present before have become much more numerous. Plant diseases have multiplied in number and increased in virulence during the same period. We may well ask, then: Is environment (meaning the soil) a factor in their control?
Certain human and animal diseases and parasites have long been thought of as environmental. Hookworms belong entirely in the South, particularly in the south-eastern section of the United States. Malaria can occur only where the Anopheles mosquito is present. Pellagra and other so-called deficiency diseases have usually been thought of as belonging to certain localities. It has not been difficult to connect such troubles with the environment in which they have been found.
In recent years the control of deficiency diseases has been much improved in most areas because of the more general availability of protective foods. Coincident with this improvement, however, there seems to have been a general decline in the nutritive value of foods produced on average land. The discovery of vitamins has brought this matter into better focus. When knowledge of vitamins was new, it was thought that certain foods contained an abundance of particular vitamins. Egg yolk was said to be rich in most of them. Now it is known that the vitamin content of the egg yolk is seriously affected by the food consumed by the hen. Butterfat was considered to be uniformly potent as a source of vitamin A. More recent discoveries show that the vitamin content of butterfat or cream is largely dependent upon whether or not the cow has access to a quantity of grass, or to the richly coloured foods which provide her with this essential vitamin. Neither the hen nor the cow can by herself create the various vitamins she transmits to the consumer of her products. The vitamins must be supplied to each animal through food.
These disquieting discoveries -- that foods we had thought were always richly endowed with health-giving substances may themselves be deficient in certain instances -- have shifted attention to the plants, which normally would be expected to supply vitamins to the animal. It becomes a complicated chain of cause and effect: milk -- cow -- hay, grain, or grass -- soil. In other words, the blame for any deficiency goes back, in the last analysis, to the soil.
Then we discover that during the very period in which deficiency diseases are being decreased in the localities where they have been most serious, the area in which they occur seems to be widening. In the last few years certain of the deficiency diseases have been found in places where they were unknown before. And, at the very same time, we find that the soil -- life's ultimate source -- has declined sharply in its ability to nourish properly the plants upon which we depend.
Characteristically, Americans confronted by this dilemma of deficient foods have turned to the drug stores to buy vitamins. There is little doubt that the development of synthetic vitamins has served to postpone disaster for many people; but it seems unnecessary to pay for something whose value is not yet wholly unquestioned, when by properly modifying the environment in which our plants live, we can again build into our food plants all the vitamin richness they once had.
The logic of such a viewpoint is inescapable, yet it has not been investigated officially to determine whether it may be true in fact. We have experimental data to prove the necessary casual relationship between the completely nourished cow and the milk rich in vitamins and other nutrients. We know through experiment that only good feed in correct proportions and quantities can nourish the cow properly. We are just as sure, with ample experimental proof to sustain us, that only a soil that is capable of supplying a sufficiency of plant nutrients in suitable combinations can create foods richly endowed with the elements needed to produce human or animal health. We have, in other words, all the necessary elements of logic for reasoning from the good soil to the best of health, or from the poor soil to the direst of disease in the animals which consume the products of the soil, but we have not assembled those elements into the necessary whole to arrive at the logical conclusion. Our agricultural reasoning is in much the same condition as was the passenger transportation of America before the existing railway lines had been grouped into great transcontinental systems. We should be able now to take the entire "trip" from starting point (good or poor soil) to terminus (good or poor health) without having to make the local stops.
In my test work and, subsequently, in field work, I discovered that soil conditions seemed to be factors in the extent to which plants were affected by diseases and insects. The evidence was so convincing that I watched carefully for verification of the idea in commercial crop growing when the tests were repeated on a field scale. The results in the field fully confirmed the earlier deductions. I am sure that the existence or non-existence of plant diseases in certain fields is related to the condition of the soil, and that the incidence of insect damage is likewise related. No other conclusion seems possible from the amazing behaviour of insects and the absence of diseases in the crops I grew on land which had been prepared by discing in (or down) great quantities of green manure crops. Yet, despite this existing chain of experimental evidence proving the truth of every element in the necessary reasoning, we cannot accept such an unofficial decision as true until it has been proved so by properly supervised official tests. For such tests we shall look to the experiment stations which have been established for that purpose.
While the presence or absence of insects or diseases seems not to be necessary to this reasoning, an important purpose will be served by dependable knowledge of just how completely their behaviour indicates the suitability of the soil in which the plant is growing. If insects and diseases prove to be a perfect index, as they must if they are truly environmental, then an entirely new "soil-testing" method becomes available to the farmer. Whenever his crops become infested by insects or are attacked by disease, he may know immediately that further green manure treatment will be helpful.
Since in ordinary farming and horticulture the fight against pests of all kinds has partaken of the inevitable, how, it may be asked, can a method of soil preparation possibly result in a change for the better? I had to find an answer to that question before I could accept the idea. The answer was difficult to find. No official experimentation by soils experts had been carried out on land prepared by surface incorporation of great quantities of organic matter. All experimental plots had been ploughed, if there was much organic matter to be disposed of. Discing has been considered feasible only where there was little rubbish or crop debris involved. Experiment station results, therefore, supplied nothing directly bearing on the case.
To me it seemed necessary to assume that the soil in which organic matter in great quantities was decaying would be richer by the quantity of decay products that had been accumulated in it. As organic matter decays, mineral plant-foods are released, as are also the additional elements which make up the organic compounds of which the living material had been composed. Depending upon the character of the organic material, decay may take place quickly or slowly. In either case, unless there are roots present at the time the decay products are set free, these used plant-foods are almost certain to be flushed out of the soil by the very first rainfall. The only certain way to prevent this loss is to have roots of growing plants always present when decomposition is going on in the soil. On land that is left undisturbed, nature takes care of this. Roots are always present; therefore, no plant food is leached away.
On the farm, these salvaging roots may be those of beans, cucumbers, or any other crop the farmer wants to grow. The roots of such crops will gratefully absorb all the decay products they can get. It is a reasonable assumption that the soil solution these roots pick up from decaying organic matter is different from that that they would find available in pure mineral soil where nothing is rotting. Decaying material in the soil enriches the soil solution, so that each unit of liquid can supply several times as much plant food as the same quantity of water from soil not enriched by decay. That is only common sense.
It follows that the more decaying material there is in the soil, the richer the solution these roots pick up will be; the richer the soil solution carried in by roots, the richer in minerals the plant sap will be. From this point it is easy to assume that variations in the richness of the plant sap may affect the attractiveness of the plant for its customary parasites. A greater proportion of minerals in the sap may result in its carrying less sugar, and a decrease in sugar content may easily make the plant sap distasteful. Possibly cucumber beetles, for example, could be starved for lack of palatable juices, even when their host plant is enjoying the richest possible food from the decay in progress in the soil.
Such a theory is not entirely without foundation in science, even though no specific research has been devoted to it. We do know that variations in internal juices of plants are produced by variations in the fertilizer treatment and in the available moisture of the soil. This fact was established in 1918 by Dr. Kraus and Dr. Kraybill, whose report has been used by a generation of students as a reference work in horticulture. [E. J. Kraus and H. R. Kraybill, Vegetation and Reproduction, With Special Reference to the Tomato, Oregon Bulletin 149, 1918.] There is no question that changes in plant composition are produced by changes in the nutrients available in the soil. We cannot, of course, know how insects feel about having their favourite host plants overfed on minerals that originate from decay. We can only guess, from the fact that they prefer the scantily fed plants to those that are better fed, that the richer sap is less palatable to the insect.
If this theory is tenable, the human race is extremely fortunate. It becomes possible, because of this relationship between the insect and its food supply, to improve the human food supply by the very method that will starve the insects.
Apparently diseases yield even more completely to the environmental conditions which are most favourable to plant growth. I am unable to advance, as tenable, a reason for this. It appears, however, that the leaf surface of fully nourished plants is better fortified to prevent the entrance of infections. That there is a difference in texture of the leaf surface of well-nourished plants compared with those growing on thin land may easily explain their better resistance to disease. In this connection, the natural resistance of healthy, well-nourished plants becomes entirely logical.
It is reasonable to believe that insects and diseases thrive only in a suitable environment, just as do other living things. Further, it appears that the environment that is best for the disease and the insect is poorest for the host plant; and the conditions that favour the host plant's development are intolerable for insects and diseases.
Scientific men with whom I have discussed this theory are not inclined to agree, because they still think the type of soil would be an important factor and doubt that the experience would be the same under other soil conditions. My contention is that the one determining condition is the surface incorporation of great quantities of organic matter, that any type of soil so treated would bring similar results -- provided other conditions were no less favourable than they were for my 1940 tests. (It can be said truthfully that the seasonal conditions from July 12, 1940, to frost were such that many other plantings of beans had to be abandoned in the neighbourhood where my beans thrived.)
Next: 13. Weedless Farming
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