Fate and transport of pesticides in a Virginia Coastal Plain soil

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Virginia Water Resources Research Center, Virginia Polytechnic Institute and State University

The fate and transport of atrazine, metolachlor, and bromide as a tracer, were characterized through surface runoff monitoring and soil core sampling on no-till and conventionally tilled field plots planted with corn. A rainfall simulator was used to generate a surface runoff event within 48 hours of pesticide application. In comparison with the conventional-tillage plot, the no-till plot yielded 32% of the runoff volume, 8% of the sediment, and 50% of the pesticide mass. Total losses of atrazine and metolachlor in surface runoff were 0.5-1 .5% of the amount applied, with the greatest losses associated with conventional tillage. Significant precipitation in the early stages of the study resulted in rapid leaching of the chemicals in both plots. Statistical tests show that chemicals moved deeper in the no-till plot, as compared to the conventional-tillage plot, in the first two weeks after application. However, statistical analysis of the remaining period shows no consistent differences in pesticide concentrations in the soil profile based on tillage practice. Atrazine dissipation was higher in the no-till plot, and there was a significant carryover of the pesticide in both plots at the end of the 157-day period.