Validation of the pesticide leaching model PELMO using lysimeter studies performed for registration

The performance of simulation models to predict the amount of leached water, pesticide concentrations in soil and pesticide concentrations in the leachate from 39 lysimeters columns with undisturbed soil cores is described in this paper. The behaviour of 14 pesticides plus 1 metabolite was investigated mainly on loamy sand soils at four different locations in Germany. In three lysimeter studies a silty loam soil was used. The annual amount of precipitation ranged from 706 mm to 1393 mm (rainfall plus additional irrigation), 85 per cent of the experiments received a minimum precipitation of 800 mm. The Koc values of the pesticides were between 5 and 4000, the mean DT(50) values in soil ranged from 5 to 120 days. The model calculations were performed with three different computer models: PRZM-1, PELMO 1.5 and PELMO 2.0. The model PELMO 2.0 predicted amounts of cumulated leachate with a mean absolute deviation of 134 mm (relative deviation factor of 1.37) more exactly than PRZM-1 (absolut e value 194 mm, relative value 1.59) and PELMO 1.5 (absolute value 205 mm, relative value 1.51).