| This study had two distinct objectives related to modeling the fate and efficacy of cotton and soybean herbicides. The first part was a greenhouse study to relate fluometuron concentration in soil to control of four cotton weeds. The weeds evaluated included: pitted morning-glory, redroot pigweed, prickly sida, and common cocklebur. Weed control was significantly correlated with fluometuron concentration with each weed and the relationship was linear, with increasing weed control with increasing fluometuron concentration. The second part of the study evaluated the ability of PRZM (Pesticide Root Zone Model), designed to predict the movement of pesticides in the root zone, to predict losses due to overland runoff. Erosion plot results determined that 1.7% of applied metribuzin and 1.5% of the applied metolachlor moved off-site in runoff during one month. PRZM, after careful selection of model parameters, predicted that 46% of metribuzin and 53% of metolachlor would leave the plot in runoff. These results indicate that under these conditions and without calibration, PRZM was unable to adequately predict the loss of these herbicides due to runoff. |
