Introduction Pesticides are widely used to control pests that affect agricultural crops and pests in homes, yards and gardens. These chemicals, classified for the kinds of pests they control, include insecticides, herbicides, fungicides, nematicides, rodenticides, miticides and soil fumigants. Pesticides generally are man-made organic compounds. In some cases, pesticides used for plant protection may be applied to soil before planting, while for others, the application is made after seeding. Usually, most of the applied chemical comes into contact with soil.
Application is by spraying a liquid, broadcasting granular formulations, or fumigation.
Concerns about environmental and health issues related to pest control make it important to understand the possible hazards associated with their use and to minimize risks. The fate of pesticides in soil is controlled by chemical, biological and physical forces. The downward movement of pesticides through the plant rooting zone of soil reduces their concentrations in the surface soil but may ultimately lead to ground water contamination. Absorbed pesticides are stored in the tissue of organisms, a process called bioaccumulation, or transformed by enzymes of the organisms. Pesticides remain or persist in soil for a limited time.