Earth, Climate & Environment

Soil Management

.
Soil Management is the basis of all scientific agriculture, which involves six essential practices: proper tillage; maintenance of a proper supply of organic matter in the soil; maintenance of a proper nutrient supply; control of soil pollution; maintenance of the correct soil acidity; and control of erosion.

TILLAGE

The purpose of tillage is to prepare the soil for growing crops. This preparation is traditionally accomplished by using a plow that cuts into the ground and turns over the soil. This removes or kills any weeds growing in the area, loosens and breaks up the surface layers of the soil, and provides a bed of soil that holds sufficient moisture to permit the planted seeds to germinate. Traditional tillage may harm the soil if used continuously over many years, especially if the fertile topsoil layer is thin.

MAINTENANCE OF ORGANIC MATTER

Organic matter is important in maintaining good physical conditions in the soil. It contains the entire soil reserve of nitrogen and significant amounts of other nutrients, such as phosphorus and sulfur. Soil productivity thus is affected markedly by the organic-matter balance maintained in the soil. Because most of the cultivated vegetation is harvested instead of being left to decay, organic materials that would ordinarily enter the soil upon plant decomposition are lost. To compensate for this loss, various standardized methods are employed. The two most important of these methods are crop rotation and artificial fertilization.

NUTRIENT SUPPLY

Among soil deficiencies that affect productivity, deficiency of nutrients is especially important. The nutrients most necessary for proper plant growth are nitrogen, potassium, phosphorus, iron, calcium, sulfur, and magnesium, all of which usually exist in most soils in varying quantities. In addition, most plants require minute amounts of substances known as trace elements, which are present in the soil in very small quantities and include manganese, zinc, copper, and boron. Nutrients often occur in the soil in compounds that cannot be readily utilized by plants.

SOIL POLLUTION

Soil pollution is the buildup in soils of persistent toxic compounds, chemicals, salts, radioactive materials, or disease-causing agents, which have adverse effects on plant growth and animal health. As of now, soil pollution is not widespread. Although the application of fertilizers containing the primary nutrients, nitrogen, phosphorus, and potassium, has not led to soil pollution, the application of trace elements has. The irrigation of arid lands often leads to pollution with salts. Sulfur from industrial wastes has polluted soils in the past, as has the accumulation of arsenic compounds in soils following years of spraying crops with lead arsenate. The application of pesticides has also led to short-term soil pollution. See Environment.