The soil is naturally classified in two ways: first, as to the amount of plant food contained; second, as to its mechanical condition—the relative proportions of sand, decomposed stone and clay, of which it is made up, and also the degree to which it has been broken up by cultivation.
The approximate amount of available plant food already contained in the soil can be determined satisfactorily only by experiment. As before stated, however, almost without exception they will need liberal manuring to produce good garden crops. I shall therefore not go further into the first classification of soils mentioned.
Of soils, according to their variation in mechanical texture, I shall mention only the three which the home gardener is likely to encounter. Rocks are the original basis of all soils, and according to the degree of fineness to which they have been reduced, through centuries of decomposition by air, moisture and frost, they are known as gravelly, sandy or clayey soils.
CLAY SOILS are stiff, wet, heavy and usually "cold." For garden purposes, until properly transformed, they hold too much water, are difficult to handle, and are "late." But even if there be no choice but a clay soil for the home garden, the gardener need not be discouraged. By proper treatment it may be brought into excellent condition for growing vegetables, and will produce some sorts, such as celery, better than any warm, light, "garden" soil. The first thing to do with the clay soil garden, is to have it thoroughly drained. For the small amount of ground usually required for a home garden, this will entail no great expense. Under ordinary conditions, a half-acre garden could be under-drained for from $25 to $50—probably nearer the first figure. The drains—round drain tile, with collars—should be placed at least three feet deep, and if they can be put four, it will be much better. The lines should be, for the former depth, twenty to thirty feet apart, according to character of the soil; if four feet deep, they will accomplish just as much if put thirty to fifty feet apart—so it pays to put them in deep. For small areas 2-1/2-inch land tile will do. The round style gives the best satisfaction and will prove cheapest in the end. The outlet should of course be at the lowest point of land, and all drains, main and laterals, should fall slightly, but without exception, toward this point. Before undertaking to put in the drains, even on a small area, it will pay well to read some good book on the subject, such as Draining for Profit and Draining for Health, by Waring.
But drain—if your land requires it. It will increase the productiveness of your garden at least 50 to 100 per cent.—and such an increase, as you can readily see, will pay a very handsome annual dividend on the cost of draining. Moreover, the draining system, if properly put in, will practically never need renewal.
On land that has a stiff or clay sub-soil, it will pay well to break this up—thus making it more possible for the water to soak down through the surface soil rapidly—by using the sub-soil plow. (See Chapter V.)
The third way to improve clay soils is by using coarse vegetable manures, large quantities of stable, manures, ashes, chips, sawdust, sand, or any similar materials, which will tend to break up and lighten the soil mechanically. Lime and land plaster are also valuable, as they cause chemical changes which tend to break up clayey soils.
The fourth thing to do in treating a garden of heavy soil is to plow, ridging up as much as possible, in the fall, thus leaving the soil exposed to the pulverizing influences of weather and frost. Usually it will not need replowing in the spring. If not plowed until the spring, care should be taken not to plow until it has dried out sufficiently to crumble from the plow, instead of making a wet, pasty furrow.
The owner of a clayey garden has one big consolation. It will not let his plant food go to waste. It will hold manures and fertilizers incorporated with it longer than any other soil.
SANDY SOIL is, as the term implies, composed largely of sand, and is the reverse of clay soil. So, also, with the treatment. It should be so handled as to be kept as compact as possible. The use of a heavy roller, as frequently as possible, will prove very beneficial. Sowing or planting should follow immediately after plowing, and fertilizers or manures should be applied only immediately before.