Abstract
Nonpoint source pollution from agriculture affects both surface water and ground‐water quality. Water quality degradation is caused by erosion and sediment, animal wastes, fertilizers and pesticides. Best management practices that control runoff and erosion will reduce particulate nitrogen and phosphorus loads but may increase nitrate losses in subsurface drainage. Only applying enough nutrients to meet crop needs will reduce nitrogen and phosphorus losses. Nonpoint source pollution from animal agriculture may result from animals grazing, open animal confinement feedlots, and manure disposal areas. In most cases pollution from feedlots is greater than from manure application sites or grazing areas. Pesticides with solubilities of greater than 10 ppm are lost mainly in the water phase of runoff. Runoff and erosion control best management practices will reduce pesticide losses in surface runoff.