Validity of agroecosystem models a comparison of results of different models applied to the same data set

The simulation results obtained from 19 participants of the workshop “Validation of Agroecosystem Models” were compared and discussed. Although all models were applied to the same data set, the results differ significantly. From the results it can be concluded that the experience of a scientist applying a model is as important as the differences between various model approaches. Only one model simulated all main proceesses like water dynamics, plant growth and nitrogen dynamics with the same quality, the others are able to reproduce the measured dynamic only in parts.