The application of soil water and nitrogen balance model SIMWASER/STOTRASIM (Stenitzer, 1988; Feichtinger, 1998) requires detailed knowledge of the water retention and unsaturated soil hydraulic conductivity properties of the considered soil profile as well as plant characteristics of the considered crop rotation. Before the model can be used for scenario testing or prediction, it needs to be calibrated, which means the adjustment of the input parameters to match the model to measured data. The objective of this master thesis was to develop a tool for the automatic calibration of SIMWASER/STOTRASIM. For this purpose the model, written in C#, was coupled with the Multiparameter Optimization Tool AMALGAM, coded in MatLab. The task was performed by developing systems of data transfer between MatLab and C#, working out an alternative for the representation of the hydraulic conductivity and water retention characteristics with model parameters, defining objective functions, setting starting values and ranges and developing simple structures for data input and result output. The software package is called Calisto (‘Calibration Stotrasim). Application tests show that the software is executable and can be used for the calibration of the parameters ‘potfak (mineralization multiplier), ‘rs (evaporation coefficient) and for the parameters that describe plant development. The occurrence of two systematic errors, however, impeded optimization of the soil parameters. A solution to fix these problems would require further studies.