THE INFLUENCE OF NITRATE REDUCTION STRATEGIES ON THE TEMPORAL DEVELOPMENT OF THE NITRATE POLLUTION OF SOIL AND GROUNDWATER THROUGHOUT GERMANY - A REGIONALLY DIFFERENTIATED CASE-STUDY

A GIS-based area-differentiating model has been used to analyze the ni trate pollution of soil and groundwater throughout Germany. The result s of the calculations based on the model for the current situation sho w that a high potential for high nitrate pollution of the soil and gro undwater (> 50 mg NO3/l) is to be expected in all regions of Germany s ubject to intensive agricultural use. In order to achieve a sustainabl e use of water resources, effective strategies to reduce the nitrogen surpluses from agriculture must be developed and analyzed with respect to their spatial and temporal impact on the nitrate pollution of soil and groundwater, taking into consideration the various agricultural l and usages as well as the different hydrological, hydrogeological and agricultural conditions. The effects of three different nitrate reduct ion strategies on the resulting N-surpluses and the nitrate concentrat ion in the leachate were investigated; firstly a stocking rate limitat ion, secondly a limitation of both organic and mineral fertilizers and thirdly, a combination of three reduction measures consisting of a st ocking rate limitation, an improvement of the nitrogen utilization fac tor by livestock and a higher utilization factor of nitrogen bound in organic fertilizers by crops. The analysis showed that separate applic ation of each of these nitrogen reduction measures would only lower th e nitrogen surpluses in a few regions. In order to achieve a considera ble reduction of nitrate concentrations both in leachate from land und er agricultural use and in the groundwater a combination of area-cover ing and regionally effective measures (scenario III) turned out to be most promising.