Water run-off quickly creates gullies in sloping land not covered by vegetation. Such land can be restored by gully reclamation. Small gullies can be seeded with quick-growing plants such as oats, barley and wheat to reduce erosion. In deeper gullies small dams can be built to collect silt and gradually fill in the channels. Rapidly growing shrubs, vines, and trees can be planted to stabilize the soil. Channels built to divert water away from the gully will prevent further erosion.
Erosion caused by exposure of cultivated lands to high winds can be reduced by windbreaks, or shelterbelts, long rows of trees planted to partially block wind. They are especially effective it land not under cultivation is kept covered with vegetation. Windbreaks also provide habitats for bird’s pest-eating and pollinating insects, and other animals.
Maintaining and Restoring Soil Fertility:
Organic fertilizers and commercial inorganic fertilizers can be applied to soil to partially restore and maintain plant nutrients lost by erosion, leaching, and crop harvesting and to increase crop yields. Three major types of organic fertilizer are animal manure, green manure, and compost. Animal manure includes the dung and urine of cattle, horses, poultry and other farm animals. In some Less Developed Countries human manure, sometimes called high soil, is used to fertilize crops.
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Application of animal manure improves soil structure, increases organic nitrogen content, and stimulates the growth and reproduction of soil bacteria and fungi. It is particularly useful on crops of corn, cotton, potatoes, cabbage and tobacco.
Despite its effectiveness, the use of animal manure in the world has decreased. One reason is that separate farms for growing crops and animals have replaced most mixed animal-and crop-farming operations. Animal manure is available at feedlots near urban areas, but transporting it to distant rural crop-growing areas usually costs too much. In addition, tractors and other motorized farm machinery have replaced horses and other draft animals that naturally added manure to the soil.
Green manure is fresh or growing green vegetation plowed into the soil to increase the organic matter and humus available to the next crop. It may consist of weeds in an uncultivated field, grasses and clover in a field previously used for pasture, or legumes such as alfalfa or soyabeans grown for use as fertilizer to build up soil nitrogen.
Compost is a rich natural fertilizer; farmers and home owners produce it by piling up alternating layers of carbohydrate-rich plant wastes (such as cuttings and leaves), animal manure, and topsoil. This mixture provides a home for micro-organisms that aid the decomposition of the plant and manure layers.
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Today, especially in the United States and other industrialized countries, fanners partially restore and maintain soil fertility by applying commercial inorganic fertilizers.