Nonpoint source pollution is both a relatively recent concern and a complex phenomenon with many unknowns. Knowing the extent to which agricultural sources contribute to the total pollutant load, the extent to which various control practices decrease this load, and the effect of reducing the pollutants delivered to a water body are basic to the achievement of water quality. The purposes of this guide are to provide information on the control of nonpoint sources of pollution from agricultural lands and to incorporate a water quality perspective into conservation planning and education. This guide covers agricultural lands and addresses the most common land uses: cropland, hayland, pastureland, rangeland, and woodland. It does not cover acid mine drainage or dryland saline seeps. It focuses on five major classes of pollutants from agricultural nonpoint sources and how they move into receiving waters. A glossary of applicable terms is appended. Twenty-six references are listed. (CW)