|
 |
|
|
3. Soil Is Not Eroded
IN a very important sense, soil does not erode, for the more or less pure minerals that are left after all the organic matter has disappeared from the land are not, properly speaking, soil at all. They are merely the raw materials from which soil was originally made and from which it can be made again. Erosion begins only after the soil surface has become virtually non-absorbent -- a condition induced by the compactness resulting from the loss of highly absorbent, cellular organic matter present in nearly all undisturbed soils.
In native meadow or forest, rainfall -- even the most torrential -- strikes the spongy mass of humus and is held, with little or no run-off. Wherever there is run-off, the movement is retarded and ultimately halted by the successive areas of absorbent organic matter over which the water moves. In a tight soil, free from organic matter, erosion is almost inescapable because the very tightness of the soil defeats the gravitational movement of water.
Equally, a soil surface nicely charged with organic matter -- decayed vegetable growth, plant tops, and dead and still living roots of all kinds -- is poor field for the forces of wind erosion which have been so destructive in certain western states. But a soil which has been impoverished of organic matter is all too often gone with the wind.
Human generations are too short for us to have actually witnessed the complete cycle from virgin to eroded soil. William Byrd, the Virginia landsman of the eighteenth century, described the portion of this cycle that most people today have never seen. The following account of corn planting by a farmer of the early days is quoted from Ben Ames Williams' Come Spring:
He early cleared a patch of land and planted corn as soon as he had done his burning. The green wood was not consumed by the fire, and charred carcasses of trees lay everywhere; but he did his planting among them, poking a hole in the ground with a sharpened stick, dropping in two or three kernels, brushing earth into the hole with his foot. (From Come Spring, by Ben Ames Williams, Boston, Houghton Mifflin Company, 1940, 111.)
By great good fortune, I have witnessed the planting of a number of fields of corn in our own time by much the same method as that given above. Prodigious crops can be produced by such apparently careless methods in such an environment. Two hundred and fifty bushels per acre are an easily possible yield. Farmers' Bulletin No. 400, issued by the United States Department of Agriculture but now long out of print, describes a corn yield in South Carolina that measured up 239 bushels per acre. It is certain that even this yield is well within present possibility.
Such highly productive land did not erode. It could not. There was no clean, smooth surface such as we now know. The entire depth of soil, perhaps ten to fifteen inches of it, was filled with visible organic fragments or was stained with the fine black smudge which represents the final stages of organic decay in the soil. This material was highly absorbent, to the last black stain. Such substance would scarcely permit a single drop of an ordinary rain to escape over the surface. There was too much empty space to be filled within the organic matter itself. Indeed, little water drained down through this material until it had taken in all it could hold. The depth of the black zone and the amount of water it already held determined how much additional water could be absorbed. In periods of very heavy rainfall most of the water would go on through this mass, of course. There could be no runoff water, except in long-extended wet periods. Even then the runoff water would not be stained with clay. It would be as clear as crystal -- quite different from anything we see today. The surface drainage from cultivated lands in our time is always the colour of the land.
It will perhaps be objected that when this mass becomes frozen solid no more water can get into it than can penetrate any other solid mass. This is true -- if the mass becomes frozen solid. But it is difficult to freeze such a mass solid enough that water cannot penetrate it. There are two very good reasons for this:
- The water retained by fragments of organic matter is held within the fragments, leaving open spaces between them. Examine a saturated straw pile. There is no water between the straws, though the straws themselves will be full. Even when this water is frozen, there still is plenty of open space throughout the mass.
- Such a mass of organic matter is so perishable that decay processes are continually in progress, except when there is too little heat or too little moisture. To some extent these fermentation processes provide their own necessary heat. (Remember in this connection that gardeners depend upon the heat of fermenting manure to keep up the temperature of their hot beds.) This ability to maintain higher temperatures, even in winter-time, shortens the period during which a highly organic soil can be frozen.
There are other influences that conspire to prevent tight freezing of a soil that is chiefly organic matter. A covering of snow is the best kind of insulation against the much colder upper air. Soil will often remain unfrozen through a long, cold winter in temperate latitudes, provided it is covered by enough snow. It is well known that snow falling on weeds or any other kind of organic matter is more apt to remain snow than it would if it fell on moist, unfrozen mineral soil. When snow falls on the latter, it immediately dissolves, much as it would if it fell into water; yet at the same time, that which falls on grass, boards, rail fences, roofs, or any other dry substance may accumulate rapidly and remain undissolved. Soil which is highly organic in character, similarly, accumulates snow more readily, because it always presents a drier surface. It is reasonable to believe that throughout the winter it retains a thicker blanket of snow than the pure mineral soil; and with the coming of spring the heat of fermentation within the soil will more quickly thaw out any frozen layer that might exist near the surface. This improves internal conditions for water penetration.
It has long been known that relatively little water escapes from a forest floor as runoff. Just why this is true has been a matter for conjecture, though part of the explanation at least was advanced earlier in this chapter. A commonly held theory is that the organic matter hinders the progress of the water over the surface of the minerals in the soil, thus allowing more time for the minerals to soak it in. Doubtless there is some such effect. It may be more important than I think. It certainly is true that much of the water soaks directly into the leaves and other plant residues which are found on the ground. And we know that the entry of moisture into leaf tissue is much easier than into mineral soil.
It may not be generally known that when water penetrates mineral masses it does so by finding its way between the particles. The tiny particles of clay, silt, or sand are almost completely exclusive. Water cannot enter them. It can only cling to their outer surfaces. This is extremely important information to keep in mind in a study of soils, for organic matter, by contrast, literally pulls liquids into itself. Volume for volume, then, organic matter can hold many times as much water as can any kind of soil mineral; for organic matter is chiefly open space internally, while minerals are dense, solid crystal; a fateful distinction where water relations are concerned.
The idea is abroad that man is the lord of creation -- that he dominates the earth. In certain minor respects this may be true, but in the main it is the purest propaganda; as ineffectual, when we examine the facts, as whistling in the dark. Consider the single example of erosion. The alarm of thinking men today, when they consider the plight of coming generations starving on eroded soil, borders on panic. What would they think if there were immediate prospects of a renewal of the worldwide erosion which originally sculptured the present features of the earth's surface? That was erosion with a vengeance -- millions on millions of years of it. Mountains were buried in the sea by the tearing down of the original fire-formed stone of which they were composed, and the removal of the debris by the unhindered waters and winds which shuttled back and forth across such continents as then existed. Geologists still puzzle over the wreckage, trying to piece out the story.
That original large-scale erosion was finally curbed. But it was not done by that self-advertising animal called man. It was done by vegetation -- plants. Plants, the conquerors, had to start from nothing but powdered rock. Some structural materials they extracted from the minerals themselves, some from the air and the rays of the sun, and the rest from water. The porous architecture they were able to create from these materials is still the wonder of existence, though so commonplace as not often to be even an object of curiosity. A casual glance at a bit of onion skin, or a few strands of algae, under a microscope is a revelation to the uninitiated, even though no further thought is given to it. If it is considered that this delicate, lacy network of cells could not be possible except for the presence in infinitesimal amounts of such chemicals as phosphorus, iron, sulphur, calcium, potassium, and magnesium, the miracle of life becomes apparent. To know, then, that world-wide erosion was curbed in the beginning by stuff similar to that on the microscope slide should give us a healthy respect for all plants and for their disintegrating remains; for, down to the last black colloidal remnant of the dead plant or animal tissue, organic nature continues to fight erosion by the trick of absorption. By eternally coaxing water to enter, organic tissues keep it under control. Hence the importance of having the organic tissues where the water can reach them the instant it hits the earth as rain.
Plants are the real masters of the earth. Independent of human management, since they antedated the race, plants came spontaneously from the sea and threw a restraining influence over the unstable surface of the land, quieting its restlessness. Botanists explain the process in detail and with plausible reasoning, allowing eons for the lapse of time from the first single cells to the giant sequoias, and other eons for suitably equipped plants to complete the vegetative mantle over the earth. Moses offers a different story, of course, but be that as it may, we can be sure that man will master the rest of creation only as he comes to terms with plants, the real masters. They hold the key to his food supply.
Admittedly, we have serious erosion to contend with now. Much of our land is again in almost precisely the condition all land was in before plants arrived. It is bare, and it is in movement. Yet the present situation is immeasurably more favourable than the earlier one. The same destructive forces of wind and water are at work now as then, but the forces of plant opposition are now fully organized and mobilized. Alone, unless interfered with by man, plants can reclaim wayward land in an infinitesimal fraction of the time that was required eons ago, before they had adapted themselves to such work. Even so, such a reclamation period, when measured in terms of human lifetimes, may be excessively long. We are likely to get hungry waiting for natural forces alone to stop erosion and restore soil to the eroding mineral surface. Men must lend a helping hand.
The processes by which vegetation accomplishes a new cover where the previous cover has been destroyed are neither secret nor mysterious. All botany texts and a variety of other scientific treatises discuss the influences that determine the development of plant communities. These factors have been so ably discussed elsewhere that there is no necessity for my doing so here. It may be pertinent, however, to introduce some of the underlying principles which determine the nature of plant successions as they occur.
Important among the life factors that occasion the growth of one plant as against another in a given location are the requirements of the species for water and for heat. Although the temperature of the air is influenced to a certain extent by the soil, we may pass it over, because it is not of major concern. Water, being literally managed by the surface upon which it falls, becomes the key factor to be discussed. Moreover, the manner in which the supply of water available for future plants is increased or decreased from year to year as a result of changes wrought by successive generations of plants on the site is an important consideration for us.
The earliest plants to occupy an area are composed of a more or less spongy tissue capable of absorbing and holding water for future need, in addition to that being used currently. This reserve water is supplied to the active plant tissues as required, and saves the plant from extinction when its roots have exhausted the supply of water in the soil. Such are the lichens and mosses. Their remains, unless whisked away by the wind, accumulate from year to year. In a few years the soil itself will necessarily have become intermixed with these spongy remains, so that many times more water will be retained in the soil than could be held by the pure minerals in the beginning. This additional water makes the living lichens thrive, which in turn further increase year by year the accumulated sponginess in the soil itself. If there were no other kinds of plants in the world, it is easy to conjecture that these pioneer plants might develop to giant sizes, like the cacti of the desert.
Miles away from this hypothetical spot where the lichen-moss drama has attracted a better water supply, another spot is covered by plants that could not possibly have endured the conditions through which lichens and mosses lived and prospered. As if by magic, seeds of these less hardy plants arrive by wind, bird, or animal. Presently the new plants annihilate the pioneers by the simple procedure of growing taller and robbing them of their essential sunshine. So the plants that prepared the way for these interlopers have to find another bare spot on which to make a new start. Later, the newcomers in their turn are driven away by other kinds even less hardy for which they have paved the way. In this evolution of plant populations on a given spot, the indispensable condition to a thriving community is increasing ability of the soil to retain rainfall.
The availability of water, while a prime consideration, is no more important than other requirements of plant growth; but it may prove the key factor in determining the degree to which a given species is provided with or exposed to other needed conditions. Thus water availability, by developing more expansive tissues, necessarily creates light limitations for low-growing plants, so that water, not the unavailability of light, becomes the primary factor in crowding out a species which fails because of lack of light. It would not be surprising to find that the presence or absence of water is the real key to situations supposedly created by other factors.
In any case, each successive stage in the laying down of an absorbent mat on the earth's surface removes one step further the possibility of runoff and erosion. It is not for nothing that writers have referred in literary contexts to "the earth's carpet," for in a very practical sense it is the carpet which covers and protects the landscape. Consider the fallen autumn leaves: snow will billow high upon them in the winter months, melt in the sunshine of spring, and yet the leaves in the center of a heap will be dry. It is the humus below which has profited, as the winter moisture has filtered slowly down, to be caught and held by the sponge of true earth.
Conventional thinking about erosion so far has centered about the idea of securing greater infiltration into the mineral soil, since that is about all that is left on many farms. We have given almost no thought to the idea of providing volumetric space in and on top of the soil into which the rainfall would be helplessly snatched as soon as it fell, thus halting erosion at its source. Two reasons have favoured such thinking:
- It has never been thought possible for planting and cultivation to be done except on a smooth surface. Hence, nobody thought to try or suggest the possibility of growing cultivated crops without first disposing of whatever rubbish littered the surface. Such rubbish was always disposed of by ploughing.
- Farmers and scientists have long known that the chief need of soils is organic matter, but that need was supposed to be met by ploughing the organic matter into the soil to a depth of six to eight inches. Nobody seemed to realize that this procedure actually robbed the following crop of virtually all the substance of this buried organic matter.
By such hapless reasoning we have preserved for generations a system of soil management which should long ago have been revised to conform to the known facts. Planting can be done in a plant-strewn surface. It had to be done so when the land was first cleared. Doubtless, it is easier to manage land which has nothing on the surface to be caught and dragged along by the sliding equipment we use for planting and cultivating. But, if the crop planted in such smooth land must necessarily produce a smaller yield because of the purity of the minerals (freedom from decaying organic matter), it seems logical to suggest the wisdom of trying to devise implements which will negotiate the surface rubbish. Equally, if crop yield is greater from a surface full of plant debris, as has been proved by official tests at the Nebraska Experiment Station, the desirability of the necessary equipment is beyond question.
We emerge with two highly important objectives well within our grasp: improved crop yield, which is immediate, and arrested erosion, which is long range but closely related to our ultimate welfare. Both are attainable by the simple procedure of abandoning the ancient practice of ploughing organic matter under and substituting instead the effective practice of leaving the matter on the surface or working it in from the top. The organic sponge on top precludes erosion and provides the substance for maximum plant growth. That which has been ploughed under leaves a denuded and tight surface ideally suited to the processes of erosion, while the nutriment for plants lies six to eight inches below their incipient roots, out of reach and therefore ineffectual for the principal purpose at hand.
It can be said with considerable truth that the use of the plough has actually destroyed the productiveness of our soils. Fortunately, however, this result may be said to be temporary. With surprising suddenness the soil which is supposedly ruined will respond with bumper crops, providing it is supplied plentifully with organic matter properly incorporated into the surface. This generous response by soil thought to be "worn out" shows that our farmland has not been exhausted by cropping but has been rendered impotent by inept management.
Our faults are oftentimes excused on grounds of necessity. Ploughing, however, can summon no such defence: there is simply no need for ploughing in the first instance. And most of the operations that customarily follow the ploughing are entirely unnecessary, if the land has not been ploughed. It is possible to farm land without a smoothing harrow, without a cultipacker, without a drag, without a roller, without a single implement which is ordinarily used after ploughing -- in preparing the seed bed. The single exception to this is the disc-harrow, which is used to incorporate the rubbish into the surface as fully as possible. If the land has been disced without previous ploughing, there are no clods whatever; consequently there is no need to use the customary smoothing equipment.
"Soil conservation" is a phrase which has been widely used but little understood. There is undoubtedly an important sense in which we must save soil losses, must prevent dissolved plant food from escaping down our streams; but that is only a minor part of the task ahead. The main job is to activate and to put into biological circulation minerals that, since the beginning of time, have been locked in the crystalline structure of rock of the earth's surface. Our failure to solve that problem generations ago resulted in our adding commercial fertilizer to land, not because the land holds none of the minerals contained in the fertilizer, but because we had not found a way to dissolve those minerals so that crops could use them. We now know how to perform this trick; so the future of soil conservation work is destined to be concerned more with releasing additional minerals from the soil rock than with saving losses which by comparison are relatively light.
Fortunately, however, the same practices which result in prying more minerals out of the rock result also in maximum saving of the previously dissolved minerals. Whether we call the method "conservation" or "proper soil management" is immaterial; but it is important that we consciously imitate the natural soil profile which always and everywhere leaves all the organic matter on or mixed into the surface.
Since ploughing cannot leave organic matter on or in the surface except under such conditions as the pioneers found when they first cleared the land (when the entire soil mass often was black with intermixed organic and inorganic materials to a depth of a foot or more), ploughing, as it is now done, is definitely out as a means of breaking the land surface.
When ploughing is stopped, erosion will stop with it, for the organic matter mixed into the soil surface will cause that surface to appropriate the rain as it falls, thus removing the flow of water which is essential to the processes of erosion. Therefore, the cure for erosion is automatic when soil is again created, for real soil -- the complete soil -- does not erode.4. Traditions of the Plough
THE answer to the question, Why do farmers plough? should not be difficult to arrive at. Ploughing is almost universal. Farmers like to plough. If they did not get pleasure from seeing the soil turn turtle, knowing the while that by ploughing they dispose of rubbish that would later interfere with planting and cultivation, less ploughing might be done. Yet farmers are encouraged to plough. Deep ploughing is approved; or, in lieu of deep ploughing, farmers are advised to cut deep into the subsoil in every furrow. Such advice comes from farm papers, bulletins, county agents, and a long list of other sources from which farmers commonly welcome suggestions and information. There should be clear-cut scientific reasons to justify a practice so unanimously approved and recommended.
If there are such reasons I have failed to find them in more than twenty-five years of search. As early as 1912, when my classmates and I were taking courses in soil management and farm machinery, we brought up the subject, quizzing professors as to why ploughing, rather than a method of surface incorporation, should be the generally accepted practice in breaking the soil. A number of answers were offered, none, however, of a scientific nature; in the end some embarrassed instructors had to admit they knew no really scientific reasons for ploughing. They suggested that the most important justifications for the practice might be that it "turned over a new leaf" for the farmer by the complete burial of preceding crop residues, thus leaving the land free from obstructions to future movements of planting and cultivating machinery.
Our experience was not unique. The editor of one of the leading American farm papers has this to say in a letter written to me on August 5, 1937: "It is a subject I became interested in about eighteen years ago. I made a two-thousand-mile trip among soil specialists and farmers and everywhere asked the question: Why do you plough? I was rather amazed at the unsatisfactory answers I received. Apparently farmers do not really know. When I summed up the answers it seemed that they had only one good reason for ploughing, and that was to get rid of weeds." (Philip S. Rose, then editor of the Country Gentleman.) That there may be good reason to doubt whether the plough does even that is indicated in an article in the January, 1941, issue of this same publication, in which one writer points out that ploughing may preserve for future germination more weed seeds than it destroys.
In all truth, the ultimate scientific reason for the use of the plough has yet to be advanced. My own position, however, has already been advanced in earlier pages of this book. If I were advising farmers on the subject of ploughing, my categorical statement would be Don't -- and for that position there is really scientific warrant. A brief review of the reasons frequently given for ploughing will give opportunity to point out the error involved in each.
An administrative officer in the department of agriculture of one of the New England states suggests in a letter that ploughing is designed to allow oxygen to reach the roots of plants; he suggests, too, that ploughed soil will not dry out so rapidly as unbroken soil. His reasons seem to cancel each other, indicating that he had not considered these two suggested effects simultaneously. Letting air into the soil is an efficient way of drying it out, particularly that portion which is disturbed. Since the roots of crops must develop first in this inverted (and necessarily dried) section of soil, it seems that my correspondent really gave a good reason for not ploughing.
This idea -- that it is necessary to let oxygen into the soil -- has been in circulation for many years. It seems that those who pass it on do not pause to examine its implications. In a world organized as this one is, air is all pervading, except where something else fills the space. There is considerable space throughout all soils from the surface down to the level of ground water. Part of it is filled with capillary water, which clings to the rock fragments themselves; but since the spaces are too large for capillary water to fill them completely, air must fill the rest. When the water table rises, this air is forced out of the soil; when it recedes again, the air re-enters. (Water table is the name given to the level of water in any sponge-like saturated pervious rock below the surface of the ground. The level rises and falls in response to seasons of great or little rainfall. This ground water is the source of supply for perennial streams and springs. It is literally filtered water, since it has to pass through several feet of soil before reaching this low level. Streams supplied entirely from the water table are, therefore, clear at all times. Farm wells must be dug deeper than the lowest level to which the water table ever falls, or they become dry during long continued droughts.)
It might be objected that more oxygen is required in the soil than can enter the undisturbed mass. Perhaps. In that case we should study the undisturbed forest floor. The surface of the soil where the giant sequoias grow was suitable for their needs a thousand years before the mouldboard plough was invented. It is not thinkable that such giants could have developed in the absence of an optimum amount of oxygen in the soil. It must be, then, that growing plants do not require more oxygen in the soil than naturally enters it in the absence of water. There may be extreme situations, for example, where the soil has been excessively compacted by the trampling of animals or people, requiring special treatment. It is not clear, however, that ploughing would be the right treatment. The freezing and thawing of soil in winter usually assists a well tramped path to grow up in vegetation the following season, unless the use of the path is continued.
Ordinarily the publications of the government and of the various state institutions can be quoted freely. The information they carry is designed for public use, and wide distribution is desirable. Ohio State University's Agricultural Extension Bulletin No. 80 is the only exception to this rule I have seen. It was copyrighted in 1928 and reprinted in June, 1940, still retaining the copyright. The reprinting of this bulletin justifies the assumption that its contents are still considered correct. Significantly, along with other government and state publications as well as the books on soils of the last decade or two, it takes for granted that the farmer knows why he ploughs. The letterpress then proceeds to describe "good" ploughing as the complete burial of all "trash" -- so complete that none is exposed even between the furrow slices. This, therefore, may be taken as the more or less official point of view.
Various books on agricultural subjects published around 1910 do give what may be considered hypothetical reasons for ploughing. Most of them are vague enough to be interpreted in a number of ways. Here is a list:
a) Soil structure is made either more open or more compact.
b) Retention and movement of water are affected.
c) Aeration is altered.
d) Absorption and retention of heat are influenced.
e) The growth of organisms is either promoted or retarded.
f) The composition of the soil solution is affected.
g) The penetration of plant roots is influenced.This list was compiled from a single paragraph of a well-known soil text which was written in 1909. Though the authors did not realize it at the time, it is a bit of literary skating around a highly dangerous subject. The intent, apparently, was not so much to give information as to indicate in what various categories the student might expect to find it. The implied assumption is that ploughing improves the soil as environment for plant roots. The practice could scarcely be justified otherwise. Just how this improvement is accomplished is left wholly to the bewildered student's imagination. And while he is trying to rationalize this puzzle he is likely to conclude that, if ploughing really does improve the soil as a site for plants, the vegetation growing so lush on unploughed land must be to some extent underprivileged. Of course, even an astute student may miss that angle. It is obvious that most of us did.
Assuming ploughed land to be better for plant growth, we should find grass growing more freely on ploughed land than on similar unploughed land near by. Weeds, too, should show preference for ploughed land. Volunteer growth should take over and develop more rankly after land has been ploughed than before. Is this so? Observation is that, until ploughed land has subsided again to its former state of firmness, plants develop in it quite tardily, if at all. When dry weather follows the ploughing, it may be weeks or even months before either natural vegetation or a planted crop will make normal growth. The fact is that "bare" land, which notably erodes worse than soil in any other condition, consists almost wholly of land that has been disturbed recently by plough or cultivating implement. The only other bare land is that which has been denuded of top soil by erosion or other forces. There is significance in the fact that erosion and runoff are worst on bare land, and that bare land is defined above.
Take a casual glance at the landscape. Not only does the unploughed land continue to support its growth nicely while the ploughed land is recovering its ability to promote growth, but even the margins of the ploughed field itself continue to support their growth. Such evidence causes the argument that ploughing produces a better environment for plant roots to backfire. The loosening up, pulverizing, and inversion process seems a first-rate way to make good soil incapable of performing its normal functions in plant growth. The explosive separation of the soil mass wrecks temporarily all capillary connections; the organic matter sandwiched in further extends the period of sterility of the soil because of dryness. Therefore, it is not strange that ploughed soil is bare. Before it is ploughed, grass, weeds, and other vegetation grow normally because there is unbroken capillary contact from particle to particle, extending from the water table to the surface. After ploughing, this source of water is completely cut off until the organic matter at the ploughsole has decayed. Hence the soil simply takes time out from its business of growing things until its normal water supply is restored. There is no mystery about it. It is only the working out of natural law. Wishful thinking is peculiarly ineffective in preventing this undesired outcome of ploughing.
Another objectionable feature of ploughing is the merciless trowelling administered by the mouldboard to that portion of the furrow slice which is brought from the ploughsole and exposed to wind and sunshine. The effect is not noticeable, and probably not damaging, if the soil to the full depth of ploughing is dry enough to crumble; but in these days, when all soils seem to become more troublesome to handle, it is seldom that spring ploughing can be done early enough, if the farmer waits for the wet spots to dry out to a sufficient depth. Too often in his haste to get the year's work started, he rushes into the ploughing while the soil glistens as it leaves the mouldboard. Some men even plough when water follows them in the furrow. Such management of the soil certainly is playing fast and loose with resources which the soil might contribute to crop growth.
Ploughing done when the furrow slice is plastic creates clods; every clod is so much soil mustered out of service for the season. The tremendous pressure necessary to separate the furrow slice from its base compresses effectively any soil that is moist enough to be plastic; and a moderate amount of clay in plastic soil serves to harden the mass upon drying so that adobe-like clods result. Smoothing implements may reduce the size of these lumps, but as clods they are likely to remain aloof from the rest of the soil throughout most of the growing season.
Such evidence of damage done by the mouldboard has passed unnoticed by farmers as well as by most other people. Several reasons may be given to account for the public's blindness to obvious faults of the mouldboard plough.
To begin with, conditions such as modern farmers face were remote indeed when the plough was first used with a crude mouldboard attachment. The land that had been cleared of trees still was not very well subdued, for it was a hopeless task to try to keep the soil free from competing weeds and shrubs while a crop was growing. The forest was forever trying to recover the lost ground, and the only really effective tools farmers had against encroaching saplings, perennial weeds, and other unwanted growth were crude hoes, mattocks, and spades. Such ploughs as they had threw the soil both to the right and to the left. They did not cover rubbish very well, much less uproot permanently the wild growth which cumbered the ground. To-day the "bull tongue" plough of the South of the United States of America is of somewhat the same design as most of the ploughs which preceded the mouldboard.
Into such an environment the mouldboard was introduced. It was a godsend. Pulled by an ox, or even by men, this plough would actually lift and invert the soil. This made it possible, by careful work, to eliminate completely the perennial weeds and some of the smaller shrubs. And, what was more important, the farmer who previously could manage only a few square rods now could raise food on an acre or more. Such an invention at a time when England was never far from actual starvation captured the imagination of rural people everywhere. It was electric in its effects upon contemporary thought. The population now could eat regularly and well, provided enough farmers could have mouldboard ploughs.
Inventions did not occur often in those far-off days. New aids to living were rare indeed. The mouldboard plough, destined to revolutionize the living conditions of world populations, marked the beginning of a new era. So completely did it fill the greatest material need of a poorly nourished mankind that it was accorded a place in people's thoughts such as is usually reserved only for saints and priests. The plough had saved humanity almost literally.
When we come to the eighteenth century we find that in England and America alike, the farmer had more trouble keeping unwanted things from growing than in getting his crops to grow. For him, then, the use of the plough was excellent strategy, because temporarily, at least, conditions were created which made it impossible for the weeds to grow. This gave the farmer time to get his root and grain crops started before the wild vegetation recovered from the setback caused by the ploughing. Once his crops were well started, the incomparable richness of the soil kept them well ahead of the weeds. Now that the richness has completely disappeared from most land in the United States, our proper strategy may well be the exact opposite of what was advantageous then. His ploughing, even though it covered a lot of organic matter, could not create for him the sandwich, organic matter profile (OMP), for there was too much depth of blackness in the soil.
The crude mouldboards of the eighteenth century could not be favourably compared with the burnished products of today's factories. Hammered out by hand at forges erected at or near the ore mines, they could become smooth only through much use. They were designed by guess after many trials and did not become stabilized to dependable shape until a century after farmers began to use them generally. Despite its shortcomings -- much easier to appraise from our perspective than from that of the contemporary farmer -- the plough was, even in its crude state, the greatest invention of the age. It dispelled hunger as the first oil lamp dispelled darkness. Aladdin's lamp could not have been more wonderful.
When in the middle of the nineteenth century the first experiment station was established at Rothamsted, England, no one seems to have raised a question whether the neat work done by the mouldboard plough might be responsible for the trouble farmers were beginning to have growing crops. The men of science who manned that first station, as well as those in charge of the state experiment stations later established in the United States, inherited an unquestioning reverence for the plough. The doctrine of the Divine Right of Ploughs passed down from generation to generation, so that the possibility that the plough might account for the waning fertility of the soil never seriously occurred to anybody along the line. For decades, to my own personal knowledge, men have sensed that the ploughing in of a layer of organic matter at the ploughsole must of necessity interfere with capillary movement; but the subconscious feeling that The Plough Can Do No Wrong apparently prevented anybody from doing anything about it. The result is that, although we have had experiment stations in America for more than three-quarters of a century, no one of them conducted tests, before 1937, designed to compare directly the effects of ploughing, on the one hand, with the surface incorporation of all organic matter on the other. Failure to do this has definitely handicapped the development of basic soil information which might easily have prevented the debacle toward which American soils have been drifting.
The failure to harmonize the implications of ordinary observations with really scientific information may be the result of historical lag, or an attitude of mind, or mere carelessness, or, finally, a combination of all three. If we consider the published recognition given to the importance of organic material in the soil surface, especially since the opening of the present century, it is difficult to avoid assessing blame, on the score of carelessness, against those who did not look beyond their immediate data to the established data gained from ploughing. This is almost implicit in the following:
The Yearbook of the United States Department of Agriculture for 1903 carries this statement on page 284: "Decayed organic matter, by itself or in combination with mineral soil, absorbs moisture much more rapidly than soil containing little or no organic matter; hence, the greater the amount of leaf mould and other litter, the more rapidly will the rain be absorbed. Rapidity of absorption is also influenced by the degree of looseness of the mineral soil. In the forest the mulch of leaves and litter keeps the mineral soil loose and in the best condition for rapid absorption."
If such a statement seems sufficiently old for its validity to be questioned, compare it with the following, taken from pages 609-10 of the Yearbook of the same department for the year 1938: "Forest litter -- the carpet of dead leaves, twigs, limbs, and logs on the forest floor -- serves in several ways. Water falling as rain on bare soil dislodges silt and clay particles by its impact. These are taken into suspension and carried into the tiny pores and channels between the soil particles as the water makes its way downward. Very shortly the filtering action of the soil causes the openings to be clogged by the particles; water can no longer move downward through the soil, so it flows over the surface carrying with it the dislodged silt and clay; and erosion is actively under way. A protective layer of litter prevents this chain of events by absorbing the impact of the falling drops of water. After the litter becomes soaked, excess water trickles gently into the soil surface, no soil particles are dislodged, the water remains clear, pores and channels remain open, and surface flow is eliminated except in periods of protracted heavy rains."
I can detect no significant difference in the meaning of the two quotations. The latter gives a more intimate picture of the processes involved, but it fully confirms the less graphic description in the earlier statement. Moreover, every intelligently conducted experiment so far undertaken in this direction confirms the truth presented.
A paragraph from a letter dated February, 1940, should be interesting in this connection: "The Department of Agriculture has long been interested in developing new methods of soil treatment which will maintain and build up the organic matter content of the soil. Studies carried out by the Soil Conservation Service at a number of locations have already produced unusually outstanding results along this line. At Statesville, North Carolina, for example, it has been found that several inches of pine needles spread over the soil surface reduced the loss of soil by erosion to a point almost beyond measurement. There was also a considerable increase in the organic matter content of the soil and indications point to a worthwhile increase in crop yields. In Nebraska subsurface tillage, which leaves straw and other litter undisturbed on the soil surface, has proved remarkably effective in reducing soil and water losses and in preliminary experiments has led to a material increase in the yield of several crops tested." This was signed by the Assistant to the Secretary of the United States Department of Agriculture. It may be said that my letter, to which this was the reply, had mentioned and asked for comment on the fact that the mouldboard plough had never been put to test for validation. No mention of the matter was made in the official reply.
The fact that no advance whatever is apparent, when the statement of 1903 is compared with those of 1938 and 1940, indicates that effort to implement the earlier findings into general farm practice has been neglected. The statements from the yearbooks refer to forest soils, of course; but that fact must not obscure the larger fact that the findings discussed concern principles of universal application. Principles which are valid in the forest are valid in the field, always; so it seems that researches into the importance of organic matter on the surface of crop land should have been started as soon as the earlier announcement had been made. If any such work was begun earlier than 1937, I have been unable to find any record of it.
Next: 5. "Research": Unsponsored... Unconventional
Back to Contents
Back to Small Farms Library index
Community development | Rural development
City farms | Organic gardening | Composting | Small farms | Biofuel | Solar box cookers
Trees, soil and water | Seeds of the world | Appropriate technology | Project vehicles
Home | What people are saying about us | About Handmade Projects
Projects | Internet | Schools projects | Sitemap | Site Search | Donations | Contact us