THE most important tool with which the gardener works is the soil on his land. The qualities of soil vary greatly from area to area, and all the information outlined in this chapter must be applied to local conditions. In general, however, soils can be divided into three categories ; claylike, sandy or silt. The ideal soil consists of a good mixture of sand, silt and clay, and is classified as good garden loam. Clay soils have the greatest water-holding capacity, sandy soils the least.

The binding material of all good soils is an organic substance called humus. Humus increases the water-holding capacity of the soil, readily absorbs the sun's rays, liberates beneficial compounds for plants from the soil and fertilizes and improves soil texture. Humus is added to the soil by the use of organic fertilizers such as manure or the product of a compost pile. Humus can be purchased directly, but the expense is usually prohibitive if it is a large area that needs treatment.

The soil is a living thing. In the tiniest area, several million animal and plant organisms carry on their appointed tasks. The greater the bacterial activity, the more fertile your soil. Fertility requires four elements: bacterial life, sun, water and food. Given the sun, all of the other elements can be added to the soil by proper treatment. Organic fertilizers provide the soil with all of the three important elements. There are a number of ways in which these materials can be added to the soil. A few of the most common and easily used follow.

The Compost Pile

A compost pile is a combination of soil and such organic materials, possibly, as manure, garbage and plant cuttings. It is prepared by first placing a layer of inactive material (dried weeds, for example), and then placing a layer of soil, alternating succeeding layers of organic material and soil to a height of about 4 feet. The width of the pile should also be from 4 to 6 feet. The compost pile should be kept well wetted-down, particularly during the first week or so of standing, and should be turned over at regular intervals. When decomposition has proceeded to a sufficient point, the compost can be spaded into the soil.

Mineral and Nonorganic Fertilizers

Organic fertilizer, such as that found in a compost pile or animal manure, can be combined with inorganic fertilizer to make the best soil food. Organic fertilizers are classified according to their content of nitrogen, phosphorus and potash. You may see a fertilizer designated 2-6-2. This means that it contains 2 parts nitrogen, 6 parts phosphorus and 2 parts potash. The numbers designating the content of inorganic fertilizers always indicate the proportions in the order noted above.