NUMERICAL AND ANALYTICAL MODEL OF PESTICIDE ROOT UPTAKE MODEL COMPARISON AND SENSITIVITIES

A numerical and an analytical model were both used to quantify pesticide root uptake in the transpiration stream of cereals. The deviation of the calculated root uptake between both models is smaller in autumn than in spring scenario of pesticide application and may be related to the water balance of the scenario. The sensitive parameter ranges of both models on soil sorption and degradation input parameters were determined. In the autumn scenario the pesticide root uptake responds sensitive for high values of the sorption parameter related to organic carbon content (Koc > 100 cm(3)/g) and for low values of the degradation half-life in soil (< 20 days). Contrary to the autumn scenario, in spring scenario the pesticide root uptake does not respond sensitive on the degradation half-life in soil. Expressions were derived to quantify the nonlinear dependency of the maximum of pesticide root uptake on chemical and scenario specific parameters. The maximum of the pesticide root uptake as function of sorption parameter depends on the degradation rate of the chemical in the autumn scenario, but almost not in the spring scenario.