Influence of Amount and Method of Irrigation Water Application on Leaching of Atrazine

F Pesticide Contamination Prevention Act authorrzed the California Department of Food and Agrculture to modify w.es of pesticides in areas where they have leached through soil to groundwater (Connelly, 1985). Leaching of agriculhuaI chemicals has been shown to occur during recharge of groundwater whereby water moves from the surface through the soil profile to a groundwater aquifer (Wehtje et al., 1984). Extensive use of irrigation in the San Joaquin Valley, CA, has been implicated in offsite movement of agricultural chemicals that has resulted in environmental contamination problems such as increased nitrate content of groundwater (Schmidt and Sherman, 1987). The amount of recharge water that results from irrigation is a function of the irrigation method used and the amount of water applied in each event (Yamauchi, 1984). Climatic and soil conditions further modify the amount of water that is avail-