EAST SAN JOAQUIN WATER QUALITY FRAMEWORK: PESTICIDE MANAGEMENT STUDIES ADDRESSING SURFACEWATER QUALITY

摘要

The East San Joaquin Water Quality Framework is located in California's Central Valley andrnamong its objectives is to support the Irrigated Lands Waiver regulatory program and to providerndata for proposed Total Maximum Daily Loads (TMDLs). Historically, chlorpyrifos andrndiazinon have been detected in Framework surfacewater in excess of proposed TMDLrnobjectives. Two studies were performed to address this issue. A chlorpyrifos irrigation studyrnwas designed to assess the potential benefit to tailwater quality using extended irrigation lagrntimes. The study artificially induced tailwater drainage in an almond orchard and evaluatedrntailwater quality using 24 (control), 48, and 72 hour lag times between pesticide application andrnflood irrigation. Extended lag times significantly improve tailwater quality compared to therncontrol. Airblast sprayers are used extensively in almond and other tree crops for application of arnvariety of pesticides, including the chlorpyrifos and diazinon. Efficient sprayer operation resultsrnin more complete product delivery and distribution in the tree canopy and less product depositedrnto the ground where it can potentially move to surface water and impact water quality. Anrnairblast sprayer calibration study was done to assess and improve the effectiveness of airblastrnsprayers in the Framework area. Ten on-site calibrations were completed using Pessl~? calibrationrnequipment. Improvements in uniformity and nozzle performance averaged 3% and 8%rnrespectively and pre- and post calibration spray distribution patterns were improved.