Comparison of PRZM computer model predictions with field lysimeter data for dichlorprop and bentazon leaching

Abstract

The objective of this project was to optimize the agreement between the Pesticide Root Zone Model (PRZM) simulations for two experiments and then use those input parameters to predict herbicide leaching in a third experiment. The actual numbers and the simulated results all pertain to lysimeter data which has previously been described. The agreement between hydrology simulation results obtained using PRZM and actual field data was optimized by (1) altering the initial soil‐water content in the soil profile and (2) adjusting the water holding capacity for each soil horizon by changing the field capacity water content to permanent wilting point water content relationship. Once hydrology parameters were adjusted for best fit, pesticide degradation rates and adsorption coefficients were adjusted to maximize agreement between observed dichlorprop and bentazon leaching. Good agreement was obtained in hydrology simulations and bentazon movement, and poor agreement was obtained with dichlorprop movement. A “blind simulation”; was then performed on bentazon movement in Lanna clay and Mellby sand soils, which indicated greater water discharge from the Lanna soil, and minimal bentazon loss (less than 0.015 mg/m²) from each soil.