plants obtain nutrients from two natural sources: organic matter and minerals. Organic matter includes any plant or animal material that returns to the soil and goes through the decomposition process. Different soil organisms feed on different organic substrates. Their biological activity depends on the organic matter supply. In addition to providing nutrients and habitat to organisms living in the soil, organic matter also binds soil particles into aggregates and improves the water holding capacity of soil. Most soils contain 2 to 10% organic matter. However, even in small amounts, organic matter is very important. Tillage is one of the major practices that reduce the organic matter level in the soil. Each time the soil is tilled, it is aerated. Soil enzymes act as biological catalysts of specific reactions that depend on a variety of factors, such as the presence or absence of inhibitors, tillage and fertilization, and can be considered as early indicators of biological changes. The incorporation of organic amendments to soil influences soil enzymatic activities because the added material may contain intraand extracellular enzymes and may also stimulate microbial activity in the soil. Integrated animal and crop production enterprises that use manure as the primary nutrient source for crop production are not without problems. Nutrient loading on a farm with an animal enterprise may exceed crop nutrient needs.
