Adding organic matter is the key to soil improvement. This increases the granulation and aeration of clay soils and improves the moisture and nutrient retention of sandy soils. It is difficult to add too much organic matter, especially if it is partly decomposed.
Almost any kind of organic matter can be used. Tree leaves, straw, hay, sawdust, wood chips, and ground corncobs are generally available and relatively inexpensive. Manures and peat are also effective.
Composted materials are better than raw, undecomposed organic matter. Various methods of composting exist. A compost pile can be made by alternating layers of organic refuse like tree leaves, straw and hay with activating layers containing decay organisms like soil and manure. The organic layers should be about 12 inches thick. Adding a high-nitrogen fertilizer to the activating layer also helps hasten decomposition, since the decay organisms require nitrogen for their metabolism. As the pile is being built, the materials should be watered and at the center of the top of the pile there should be a depression to catch rainwater. After about 6 weeks of composting, the pile should be turned over with a fork to provide a more uniform compost. The length of time required to make compost is very variable; it depends on the size of the pile, the organic materials used, the season of the year, and the quantity of fertilizer and activator used. Under favorable conditions good compost can be made in a few weeks. In other cases it may take a year or longer. Special, manufactured compost containers are available and come with instructions. Some gardeners have a pit for making compost; others use concrete blocks or boards to enclose the compost.
The quantity of compost or organic matter to be used varies with the soil problem. Ordinarily 3 to 4 bushels per 100 square feet is recommended. This should be incorporated into the soil by spading, rotovating, or plowing. Organic matter continues decomposing after it is added to the soil, so for best results, one must continually add organic matter to the soil each year.
Green manure crops are also used to add organic matter to the soil. Rye can be planted in the fall after most garden crops have been harvested, and turned under in the spring in time for spring planting. If Sudan grass or soybeans are used as green manure crops, part of the garden must be taken out of cultivation for an entire season.
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