CHAPTER VI
HOLDING AND INCREASING THE FERTILITY
OF THE SOIL
There is no one thing that the gardener so needs to keep always in mind of more importance than that the soil needs additional fertility; it does not matter how good it may have been originally or how good it was last year; this year it must have returned to it the food that was taken from it last year by the crop that was grown upon it. Any soil that is not virgin soil—soil that has never been used, and that sort of soil is not available in towns and villages if, indeed, it is anywhere in an old, settled country like ours—must have returned to it, year after year, an equivalent of the fertility extracted from it in growing the previous season's crop. It may be that the loss of many seasons must be made good, it may be that the soil was originally deficient in many, or only one, of the elements that make fertility; probably it will lack that most important element of productive soil—humus. Humus, be it understood, is that element in the soil that causes it to appear dark. What it really consists of is decayed vegetable matter and it is always found forming the top soil of virgin, or uncultivated land. It is present in large amounts in woodlands where the falling leaves and surface growth lie on the ground, year after year, and decay and form what is technically known as leaf mould. We know how admirably it is adapted to the growing of house plants, and its value is often erroneously attributed to the plant food it is supposed to contain, but its great value is not so much in its food content as its influence on the soil with which it is combined; by its presence it makes the soil retentive of moisture and this moisture in turn unlocks the chemical elements of the soil so that they become available for food. Soils that are deficient of humus, though otherwise fertile, dry out so badly in summer that unless artificially watered, they will produce little, and even where a sufficient water supply is available the result will fall far short of what would have been produced were the supply of humus sufficient.
Fortunately there are ways of restoring the humus to worn out soils and on the small area of the kitchen garden the process presents little if any difficulty. The most readily available source of humus is found in a liberal application of barnyard manure; this for the quickest and most satisfactory results should be well rotted, but not fired or leached—that is, it should have been saved in such a way that the rain has not washed the fertility out of it in the form of liquid manure, or lack of moisture caused it to heat and burn. The most satisfactory method of handling manure is under shelter in a cement bottom pit with a depression or well for the liquid contents to drain into; this is seldom available in the town or city garden, but an enclosed pen for the manure, where it can be kept in a compact pile and where water can be turned on often enough to prevent firing, answers very well; better still is it to draw the manure on the land as it is produced; this, too, is seldom practicable in the small garden, but a heavy dressing of manure can always be applied in the fall, spread evenly and allowed to lie and rot over winter and be turned under in the spring while it is wet. The rapidity of decay, and hence the availability of the plant food it contains of any vegetable matter turned under in a garden is greatly increased if it is turned under wet, dry material turned under rots very slowly and may be a detriment rather than a help to the crops that are grown over it that season. If a plant sends its roots down into a mass of dry leaves, straw or other material it has no chance to gain either moisture or nourishment and must exist on what little its surface roots can extract from the top layer of soil.
In spading manure into a small strip of land or a bed I usually allow at least one large wheelbarrow to a square yard and this proportion should be observed for the whole garden. Practically about twenty tons of manure per acre will be required for good results, market gardeners often use far more, or a large, two horse load for a strip of land fifty feet square. If the land is light and sandy the manure should be well rotted but on clay or heavy tenacious soil fresh manure gives better results as it breaks apart the particles of the soil, by the expansion caused by heating, and adds sand, which is also a mechanical disintegrant, permanent in effect.
There is another way in which humus can be immediately supplied and that is by applications of woods earth or marsh earth-muck, directly to the soil. Where a supply of either form of humus is available it pays well to employ it. For a number of years I made a practice of keeping track of available sources of humus, noting as I drove about the country where new land was being broken up and especially where marsh land was being ditched and drained; then in the spring I would engage the owner to haul me as many loads as I required, but as the time passed it became necessary to go farther and farther afield until the cost of hauling became prohibitive.
There has been considerable discussion of late in agricultural papers as to the value of raw muck when applied to the land. Muck in its unsubdued state is more of a fuel-peat than a fertilizer; it needs to be subdued by lying out over winter so that the frost may disintegrate it and make it available for plant food, but I have found that it may be made immediately available in its raw state by burying or covering it with a layer of soil to exclude the air and retain moisture; in this form it gradually changes to humus and plants grown in it do exceedingly well. Among interesting experiments conducted to test its use was this conclusive one: deep holes were dug in beds that were to be planted to bedding plants—cannas, salvias and the like; these holes were filled with the raw muck and covered with the soil of the garden and into this the plants were set and the usual culture followed; the results were surprising; salvias, that ordinarily made a growth of about thirty inches reached the astonishing height of nearly five feet and were a mass of blooms; still more astonishing results were discovered in clearing the beds in the fall when it was found that the muck had practically disappeared, the plants having literally consumed it. Left on the surface of the soil the muck would have dried into a hard, intractable mass, fit only for fuel.
If one had a supply of raw muck available and wished to apply it to the garden it could be handled by following the plough and shovelling the muck into the open furrow; the next furrow turned would cover it. It would be of much benefit and would be turned to the surface again in the following spring ploughing. This should not be expected to take the place of barnyard manure, as it would lack some elements contained in that but it could be combined with such commercial fertilizers as the condition of the soil might suggest—lime, for instance, might be indicated by the sourness of the soil. If sorrel is plentiful on the ground it is a pretty good indication that lime is in order, but one need not depend upon its presence for data as these may be quickly attained by the use of blue litmus paper which may be obtained of any druggist. Its use is simple; if the soil is very wet, simply pressing a strip of litmus paper down into it and examining it in an hour's time will indicate, according as it retains its color or turns pink—the acid reaction—the presence of acidity in the soil, or a cupful of the soil may be mixed with water to a thin paste and the paper inserted with the same diagnosis.
Lime is more in the form of a stimulant or indirect fertilizer than a real plant-food; it is in a medical sense an alterative, changing the nature of the soil. It not only sweetens, but mechanically, it binds loose soil, but flocculates or opens up tenacious clayey soils, affording freer passage of air and water and lessening the tendency to wash. It should be applied, on light, sandy soils at the rate of about five hundred pounds per acre or twenty-five pounds to every fifty square feet of garden plot; ten times this amount can be used on a heavy clay soil, but liming of the soil is not necessary every year, about once in five being desirable, so that considered as an expense it is nearly negligible. Slaked lime is best, and wood ashes, which contain about thirty-four per cent. of lime, are valuable aids in building up the fertility of the soil. They should not, however, be mixed with the manure or applied at the same time as they tend to release the ammonia contained in the manure and as ammonia spells nitrate—the most costly of all our commercial fertilizers—the ashes should rather be broadcasted over the ground after the manure is turned in and then mixed with the soil by dragging and harrowing.