Impact of Tillage, Crop Rotation, and Chemical Management Practices on Groundwater Quality

Contamination of groundwater by nitrate and pesticides has been documented by various state and federal agencies in the United States. Groundwater pollution is of increasing concern in the United States because about 50 percent of the drinking water comes from groundwater. A recent study suggested that water pollution is the most damaging and widespread environmental effect of agricultural production. Recent research conducted in Iowa and surrounding states has indicated the incidence of groundwater contamination by pesticides and nitrogen fertilizers (Baker and Johnson, 1981; Everts and Kanwar, 1990; Gast et al., 1978; Hallet al., 1989; Hallberg, 1989; Kanwar et al., 1985a, 1986, 1988, 1991). Elevated nitrate levels in groundwater because of agricultural activities also have been documented (Kanwar and Baker, 1991)