HUMUS

Every good soil contains organic matter. The most famous soils, such as those of the Genesee bottoms, the prairies of the Northwest, or the valley of the Nile River, are well stocked with the decayed remains of plants and animals, which generally impart a dark or black color. The presence of much organic matter greatly increases the productivity of any soil. The experienced farmer usually identifies a dark colored soil as a fertile one for this reason.

Organic matter in this partially decomposed and darkened condition is commonly known as humus, and is the same kind of material as that

FIG. 8.-Muck soil, which is the decayed remains of swamp plants, is especially well adapted to certain truck crops when drained and properly fertilized

which leaches from swamp and manure heaps in the form of a brown liquid. This partially decayed plant and animal material is the most valuable single constituent of the soil and the one which every good farmer strives to save and augment. It helps to keep the soil loose and friable, improves its drainage, makes it warmer than it would be otherwise, helps to hold water in a form available for crops, and renders more available the store of food which every soil contains. The maintenance of humus is accomplished by leaving as much of the crop as possible (stubble and roots) on the soil, by turning under green crops occasionally, and by the addition of manures from the stable or the factory. Without the maintenance of humus a permanently productive system of husbandry cannot be maintained.

In a few places, usually wet and swampy ones, plants have grown up, died, and accumulated with little decay until there are deep deposits of brown or black organic material rich in humus. The rawer deposits are termed peat; the more thoroughly decayed ones are termed muck. The latter, when drained, tilled, and, usually, fertilized, are able to produce large yields of some of our most valuable truck crops, such as celery, lettuce, and onions.

FIG. 9.-Soil formed by water is generally sorted and stratified, as shown in the illustration. The character and arrangement of these strata have large influence on the growth of crops

SOIL MOISTURE

Soils hold water in their pores as does a sponge, and this water is taken up by plant roots. Water is necessary as food for the plant, as a regulator of its physical condition, and as a carrier from the soil to the plant of other food elements. There must not be too much or too little water in a good farm soil. Some plants require more than others. One class of plants lives in swampy places; another, as the cactus, can live under desert climate conditions. But the great majority of crops prefer a nicely moist condition of the soil, one that holds its form when gently pressed in the hand and that contains only capillary, or film, water

between the particles. It is moisture in this latter form that is required by the roots of such crops as beans, corn, and wheat.

When the soil is so wet that water fills the pores and appears on the surface, most farm plants will not thrive. For such conditions, drainage, the drawing off of excess water, is necessary. To drain the soil, ditches are constructed, either open or with short lengths of pipe, usually clay pipe, in the bottom to permit the water to percolate away. Over 10,000 square miles of farm lands in New York require drains to render them most profitable.

When the excess of water has been cared for by either natural or artificial drainage, the remainder of the water in the soil, the capillary water, must be husbanded carefully for the use of the crop. If it becomes deficient, the crop suffers in yield and quality, even though every other condition may be favorable. In order to conserve the soil moisture tillage is required. A farmer keeps the surface, to the depth of an inch or two, loose, level, and dry by proper tillage. He calls this layer a mulch, dust blanket,” that holds the moisture in the soil below so that it escapes only through plants and thereby accomplishes its work on the way. this operation of tillage are required knowledge and skill to cultivate each particular soil, at the right time and in the right way to secure the desired results. Soils are as peculiar as folks and sometimes as obstinate.

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When good tillage will not maintain a supply of water, it may be added artificially by means of irrigation. In New York, with 35 inches of rainfall, irrigation is not often necessary, and when required it is usually on the very light sandy soils that are used for special crops, such as truck or fruit.

The two types of conditions just described may be observed if we watch any common field plant, or even a window plant, through the summer. Note when it wilts or when it is drowned, and how it behaves in each instance. Then note the corresponding soil conditions.

FOOD SUPPLY IN THE SOIL

The store of available plant food in the soil is a matter of special concern to many persons. Plants require a variety of foods, just as do cattle. They use nitrogen (which costs 20 cents per pound if purchased), phosphorus, potash, lime, magnesia, sulfur, and iron, besides the elements obtained from water and air, which are hydrogen, oxygen, and carbon. The potash and certain other materials are contained in the soil in great quantities, yet the farmer frequently rushes to the fertilizer bag at the first sign of reduction in the crop yields. The average New York soil contains 2,500 pounds of phosphorus, 35,000 pounds of potash, and 20,000 pounds of lime per acre of soil one foot deep. The average weight

of an acre foot of soil is 3,500,000 pounds. Of nitrogen, the soil usually contains several hundred, and often several thousand, pounds per acre. All this material is normally in a form not readily available, and requires manipulation in the form of drainage, tillage, etc., to release it for crop use.

The use of fertilizers, or the artificial addition of food to the soil, may be, and often is, necessary for the best results. But many farmers make

the mistake of assuming that this is the first and about the only condition of growth, whereas bad physical condition of the soil, lack of humus, poor drainage, or bad tillage, may be much more in need of consideration. Fertilizers should come only after these other conditions have been attended to. They are the means by which the store of food in the soil is made available to the plant.

It is not often possible to determine by any laboratory analysis the kind of fertilizer to which the soil will respond. The only reliable

method of determining this point is by trying different fertilizer materials on plots of the soil in the field.

OBJECTS OF TILLAGE

Good

A crop enjoys good quarters as much as does a cow or a man. quarters for the plant means good physical condition of the soil, good tilth. Good physical condition rests upon two things: the texture, or fineness, of the soil, and the structure, or state of aggregation. A sand

FIG. 11. A heavy soil in bad tilth due to unwise handling. Tramping or plowing when too wet are generally the cause of this condition. A poor place for plant growth

or gravel soil has a coarse, open texture that may be so porous as to be leachy and not hold enough water for crop use. A clay soil is fine textured and may be too compact and hard. The farmer cannot change the texture of the soil. He must make the best of it.

But the farmer can do good work in changing the structure of the soil. One cannot greatly alter the structure of sand and gravel soils. The chief aim in their tillage is to maintain as compact a structure as possible, and to keep a thin surface mulch. Clay soil, on the other hand, is troublesome because of the bad structure it tends to assume. It will puddle, bake, and then break up in great clods. In this condition it is