Simulation of water and nitrogen flows and plant growth for a winter wheat stand in central Germany

Soil and plant nitrogen dynamics, litter decomposition and plant biomass production were simulated with the SOILN model. The model was tested against measurements of leaf, stem and grain biomass and nitrogen, leaf area and soil nitrate and ammonium content. It was calibrated for the first year (1989) and validated in 1991. Parameters related to translocation of assimilates and nitrogen from different tissues to grain were estimated by calibration. The simulated plant properties in 1989 explained about 95% of the variations in measured values. A similar agreement was obtained for the validation year. The corresponding value for soil mineral nitrate in 1989 was only 38%, mainly due to problems in reproducing the dynamics in the upper 30 cm in connection to fertilization applications. In deeper layers up to 90% of the variation was explained. For nitrate in 1991 and ammonium the agreement between simulated and measured values was poor.