APPLICATION OF A SIMPLE MANAGEMENT MODEL TO SIMULATE WATER AND NITROGEN DYNAMICS

A simple model for management purposes was applied to simulate water a nd nitrogen dynamics in the plant soil system of two investigation sit es in Lower Saxony. The model considers the main processes of nitrogen mineralization, denitrification, water and nitrogen movement, plant g rowth and water as well as nitrogen uptake by plants. All soil paramet ers are generated automatically by the model using basic soil informat ion. Parameters for the plant growth model have been used unchanged fo r all cereals. For sugar beets some rough adjustments have been made t o change partitioning of assimilates within the plant. All other param eters are fixed in the model. Results of 2- respectively 3-year simula tions were compared to experimental data of soil water content, minera l nitrogen in soil, plant biomass, leaf area index and nitrogen uptake by plants. The model fits well the nitrogen dynamics on the sandy sit e, but not on the loamy site. Biomass production agrees well for cerea ls except the phase of senescence, while biomass production of sugar b eets was underestimated.