Ploughman's Folly Ploughman's Folly - EcoPort

continuous three-or four-year rotation. There are probably a few exceptional cases, but this is the general rule. The
wastage caused by ploughing usually more than balances the accumulations made in the interim. In fine, rotation
of the type described is not a cure-all for impoverished soil, and, what is more important to the thesis of this
chapter, it does not get at the water relations which are ultimately desirable.
It was shown in the last chapter that a farmer may quite abruptly step up the productiveness of his soil by simply
short-circuiting the wasteful practice of ploughing. By mixing into the surface the decayable material which the
plough would inter, the farmer sets the stage for biologically economical practices hitherto unknown to modern
farming. Aside from questions of plant nutrition, there are several ways in which the surface mixing of organic
matter brings to focus friendly forces of growth which are unable to operate when land is ploughed.
Every ton of organic matter mixed into the surface of the soil will be able to contain much more absorbed water
than it could if buried at plough depth Why? Because, being weighted down by so much less overlying soil, its
volume will be greater. And organic matter, it must be remembered, retains water volumetrically, while the minerals
of the soil must hold it only upon the outer surfaces of the particles. Water runs into organic fragments, while it
squeezes in between particles of sand, silt, and clay. We can rightly expect, then, that any absorbent material we
work into the surface of the soil will retain rain water much more effectively than would the same material if
ploughed in.
Indeed, if ploughed in, organic matter gets no opportunity to catch and hold rainfall until that water has first forced
its way several inches down between the mineral crystals. Under most conditions it is much easier for some of the
water to run off the surface than for all of it to force its way down into the soil. This means, then, that when all the
organic matter is in the surface of the soil, it is able to take in water from both above and below -- and in greater
volume because of the greater volume of the organic matter itself.
Undoubtedly the original black soils our forefathers knew could absorb directly, and as rapidly as it fell, several
inches of rainfall in a few hours. It is unlikely that very much water ever leached through the zone of surface
organic matter in those highly absorbent soils. The light, fluffy leaf mould, or the springy layer of grass roots,
gradually became filled with rain water as it fell. In this connection I like to remember the story told by one of the
best-known agronomists in this country. He was inspecting some highly organic soil lying near the top of a
mountain slope when a heavy shower developed. The slope was a little less than 45 degrees. Those familiar with
geometry will recognize this as rather steep land. This agronomist remained through the storm to observe the
course of the water as it fell. He said that, so far as he could determine, none ran off. If any did so, he said, it
certainly did not take any soil with it.
Discing heavy green manure crops into the surface of the soil, then, is an excellent way to create, precisely in the
surface of the soil, a reserve of water upon which crop roots can draw continuously until it is used up. Such an
arrangement is obviously superior to the principle of permitting the water to run down through the soil and hoping it
will be brought back by capillarity. Aside from holding a plentiful reserve of water in the root zone, the mass of
organic matter receives capillary water continually from below, which replaces, at least in part, the reserve from
which plants are drawing. This reserve supply of water serves to tide crops over extended periods of drought which
otherwise would damage them seriously. From such a source water can be made available during many more
days of the growing season than could possibly be the case when surface conditions are such as to let some of the
rainfall run off and be wasted. Here is "conservation of natural resources."
This, however, is only part of the story. The water stored in surface organic matter is constantly being used to
assist in the decomposition of the material which holds it. It not only assists in this decay, but it dissolves and in
turn holds the products released. Thus, as long as water is retained in the organic tissues, it is constantly being
enriched by the cast-off substances of which the organic matter was composed. And all of this enrichment is in
addition to the minerals which the capillary water has picked up and dissolved in the soil depths before the water
has been absorbed by the organic matter. It can readily be seen that under these conditions many influences are
working together effectively which could not do so if the organic matter were located six to eight inches deep,
where relatively few plant roots reach.
At this point the reader should recall that, in the ploughed soil, carbon dioxide is released into the upper layer of
soil; and that this gas is prevented from becoming carbonic acid because of the necessary dryness of the upper
layers. In the newer situation, with all of the organic matter just in the surface, there is provided an abundance of
water in the vicinity in which the carbon dioxide can be dissolved. And, since carbonic acid is one of the most
efficient of known natural solvents of minerals, its work in the surrounding crystalline rock particles serves to
release for plant use quantities of phosphorus, potash, and other needed plant nutrients which would not otherwise
be available.
The extent to which this release of minerals from the rock itself can take the place of applications of mineral
fertilizers is something I am not prepared to discuss. It is an interesting and a very important question. Every
farmer will want to know, and is entitled to know, the answer. If it is possible that the carbonic acid released in the
soil will supply enough fresh minerals to supplement adequately the minerals drawn from organic sources, then the