Formulation and tillage effects on atrazine and alachlor in shallow ground water in upland corn production

At the Mississippi Agricultural and Forestry Experiment Station, located at Holly Springs, the movement of atrazine and alachlor in shallow groundwater was examined under upland corn production. Both emulsifiable-concentrate and controlled-release formulations of each herbicide were used, and two tillage practices, no-till and conventional tillage, were considered. Concentrations of both herbicides decreased in shallow groundwater with increasing time after application. For initial groundwater-producing rainfall events, the emulsifiable-concentrate formation produced higher groundwater concentrations than the controlled-release formulation, and concentrations tended to be higher under no-till than under conventional tillage. In addition, weed counts in the plots receiving the emulsifiable-concentrate formulation were significantly higher than in the controlled-release plots in all years of the study.