SOIL MOISTURE NECESSARY TO FERTILITY

New Zealand Mail, Issue 1618, 4 March 1903, Page 63

SOIL MOISTURE NECESSARY TO FERTILITY

In referring to the sale of crops from the farm it is necessary to speak of selling so many pounds of plant food that should be returned to the soil, as though this were the only evil resulting from this practice. • This evil is, however, very small compared with others that result from the continual production and sale of grain crops. For when we consider that for every pound cf mineral matter removed from the soil by a crop of grain, from five to seven pounds are lost through the percolating waters, we .can readily see that the return to the soil of all the plant food taken up by the crop would only replace from 15 to 20 per cent, of what had been removed therefrom during that season. You may well aslc what supplies this enormous waste. The answer is very simple, and to find it wo have but to study nature’s methods of soil formation. >

All of our soils have originated from tho rock masses of the earth’s surface. One of the chief agents in the decomposition of these rocks was the growth and decomposition of vegetation. The decomposition of vegetable matter in tho soil .with the resulting organic acids, heat, etc., has a very powerful action in decomposing the inert mineral matters of the soil. The mechanical condition given the soil by the partially decomposed*vegetable matter also aids very materially the action of the other elements.

In tlie Eastern States, where they expend annually some 35,000,000 dollars for commercial fertilisers, tiiey have discovered that if barnyard manure is mixed, with these partly insoluble fertilisers they will be rendered much more soluble. But they seem slow in comprehending that this vegetable matter if applied to the soil will have tlie same action upon the same kind of insoluble compounds that are already there. In a recent experiment to determine the extent of this action, two boxes were filled with soil identically the same, except that to one was added 20 per cent, of its weight in cow manure. These boxes were treated exactly alike for 12 months, the soil receiving an occasional stirring. At the end of this period an analysis showed an increase of 30 per cent, in the soluble plant food of the soil to v’hicli manure was added, after making allowance for what was contained in the manure. "While that which received no" manure showed a loss’ in soluble plant food of 4.36 per cent.

Professor Snyder of Minnesota has done quite extensive work in-the way of collecting and analysing soils that have been cropped in various ways, and he finds that a native prairie soil contains about twice as much of tUe more important elements of plant- food, in a soluble form, as adjacent soils thathave been * continuously cropped with' grain for 15 or 20 years, while many that had been under cultivation fo-r much longer periods, but which bad been allowed to produce an occasional crop of timothy and clover, and had an occasional dressing of manure, were in a condition almost equal to the native soils. , « HOW VEGETABLE MATTER EFFECTS MOISTURE. • The effect of vegetable matter upon the moisture content of soils is equally as great and of no less importance. In this connection it has a two-fold effect, that of increasing the power of ~he soli

to hold water by capillary attraction, which is the water used by field crops, and at tho same timo increases the readiness with which the excess of moisture will percolate away. On soil all finely pulverised, the reduction the vegetable matter results in the land becoming more solid, more inclined to adhere in clods, and when wet more soggey and more inclined to puddio or bake.

I call to mind a case in point. Some years ago my father purchased a piece of land from a man who was regarded, by liis neighbours as being incurably lazy. There was a certain field upon this farm, originally very productive, that had been continuously grain-crop-ped until tho vegetable content was very much reduced, and upon which had recently been placed what manure had to bo moved in order to allow passago in and out of tho stable. In order to avoid any undue exertion, this manure bad not been scattered, but each load dumped in a heap by itself. Tho result was a few spots exceedingly rich in vegetable matter. The contrast was almost equal to that of an. oasis in a desert. After heavy rains the manured portions would be in a fit condition for cultivation, while water would be still standing on the soil all about them. And when the other would get ready to work it would be heavy and solid, and would not stir up into a nice mulch, while these spots would bo as loose and light as an asli heap. The plants on the manured portion would be of a rich dark green, colour, stocky and vigorous, while those beside them on tho unmanured portion would be pale, slender, and often sickly in appearance.

The greater length of time taken for* the excess of water to percolate away is a loss not only in time, which, the farmer should have the use of in his fight with the weeds, hut also in its greater injury tot the growing crop, as none of our cultivated crops will thrive or even live very long in a saturated soil. A native soil will retain about 20 per cent, more water than one that has been continuously grain-crop-ped for about 15 or 20 years. In an experiment where one-half of a sandy knoll was manured and the other not, the manured portion contained nearly 25 per cent, more water during six weeks’ drought than the unmanured portion, and at harvest time the com on the manured portion was fully two feet taller.

In another, experiment to determine the effect upon evaporation, a difference in tlie rate of evaporation was observed equal to one ton of water per acre per daiy in favour of the manured portion: Owing to the uncertainty of our rainfall in regard to time the capar city of a soil to absorb and retain water for the use of crops is very important. A certain amount of moisture is necessary before the sap will move and any, growth take place. And the nearer the moisture content becomes reduced to this point tlie less rapidly will growth take place. The variation of only a feAV per cent, in the amount of moisture retained may mean the difference between a good crop apd an almost total failure. .During the past season, which enjoyed a fairly good distribution, of moisture, we were able by the addition to a corn crop when the ears we.re forming, of four inches of water to the soil, to change the yield of com from 68 to 91.5 }iushe!s per acre. This amount of water is equivalent to a little over 5 per cent, moisture in the first four feet of soil.

In conclusion it may be said that the term, worn-out land, is a delusion. Such lands still possess plenty of plant food in an insoluble form. Lands cease to productive because their content of plant food in a soluble form has been

reduced, and they can readily he, reclaimed by the application of a sufficient amount of vegetable matter to decompose the insoluble plant food fast enough for the needs of the crops. And it is "certainly far more economical to cultivate and grow fertility than to purchase it, and not only is this kind of fertility more economical, but it is far more lasting in its effects. Very frequently the decline in productive power may he duo as much to the lessened capacity of the soil to retain moisture as to a reduction of soluble plant food, without the - aid of which the richest soil in the world has no crop-producing power. Professor Edgerton, lowa Experimental Station, in the “American Agriculturist.”