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

A numerical and an analytical model were both used to quantify pestici de root uptake in the transpiration stream of cereals. The deviation o f 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 det ermined. In the autumn scenario the pesticide root uptake responds sen sitive for high values of the sorption parameter related to organic ca rbon 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 sp ring scenario the pesticide root uptake does not respond sensitive on the degradation half-life in soil. Expressions were derived to quantif y the nonlinear dependency of the maximum of pesticide root uptake on chemical and scenario specific parameters. The maximum of the pesticid e root uptake as function of sorption parameter depends on the degrada tion rate of the chemical in the autumn scenario, but almost not in th e spring scenario.