The userʹs influence on model calibration results: an example of the model SOIL, independently calibrated by two users

Validation and calibration of complex models that simulate the soil-plant system are often assumed to depend solely on characteristics of the model. This paper compares the calibration of SOIL by two different users, based on the same set of measured data. It is shown that a reasonable fitting of the measured data was achieved with a different understanding of the system modelled and different parameter values. It is argued that the model user influences the calibration results significantly. Complex multiprocess models cannot be validated in general: they must be calibrated separately for each site, and for each different modelling objective.