By Edward H. Faulkner With a Foreword by S. Graham Brade-Birks M.Sc. (Manc.), D.Sc. (Lond.), of the SouthEastern Agricultural College (University of London), Wye, Kent. First published 1945
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.