Modeling pesticide losses with surface runoff in Germany

A model has been developed which estimates relative pesticide losses with surface runoff for all of Germany. The 42 active ingredients considered in this study were chosen according to their annual sales in 1993 (herbicides, fungicides >100 t year−1, insecticides >50 t year−1). After the construction of a nationwide data base on pesticide application rates, the runoff losses of pesticides were calculated by incorporating various spatial data sets on climate, soil, land use and other topics that have significant effects on pesticide runoff from fields. Results for the cumulative loss of 42 active ingredients applied in 11 field crops, orchards and vineyards are presented in digital raster maps (100×100 m). The model enables both a visualization of the spatial distribution of runoff risk and an assessment of the potential pollution levels originating from certain crops in specified application periods. Due to the scale of the studied area studied, the model development had to follow a strictly stochastic approach which contains some notable uncertainties. The lack of reliable information on the behaviour of the pesticides under site specific conditions constitutes the most important limitation.