The model systems HERBSIM and SIMULAT were applied to predict the dyna
mics of three different pesticides (Simazine, Metamitron and Methabenz
thiazuron) on a loam site in the Krummbach catchment, north Germany. T
he parameters of the degradation model were obtained from laboratory e
xperiments using statistical parameter estimation techniques. The info
rmation gained from this investigation were used to simulate the herbi
cide persistence under field conditions. Although not all parameters n
eeded were available from laboratory studies, SIMULAT was able to repr
oduce the field measurements of pesticide concentration without furthe
r calibration.