Impact of redox conditions on metolachlor and metribuzin degradation in Mississippi flood plain soils

The effect of soil redox conditions on the degradation of metolachlor and m etribuzin in two Mississippi soils (Forrestdale silty clay loam and Loring silt loam) were examined in the laboratory. Herbicides were added to soil i n microcosms and incubated either under oxidized (aerobic) or reduced (anae robic) conditions. Metolachlor and metribuzin degradation under aerobic con dition in the Forrestdale soil proceeded at rates of 8.83 ngd(-1) and 25 ng d(-1), respectively. Anaerobic degradation rates for the two herbicides in the Forestdale soil were 8.44 ngd(-1) and 32.5 ngd(-1), respectively. Degra dation rates for the Loring soil under aerobic condition were 24.8 ngd(-1) and 12.0 ngd(-1) for metolachlor and metribuzin, respectively. Metolachlor and metribuzin degradation rates under anaerobic conditions in the Loring s oil were 20.9 ngd(-1) and 5.35 ngd(-1). Metribuzin degraded faster (12.0 ng d(-1)) in the Loring soil under aerobic conditions as compared to anaerobic conditions (5.35 ngd(-1)).