Nitrogen leaching of integrated and ecological farming systems - scenario simulations for the estimation of local risks

摘要

The management systems of organic and integrated farming were analysed by scenario simulations with the integrated soil-crop model HERMES for 3 different soils and 2 sites with different climates regarding seepage, nitrogen leaching and nitrate concentration of the percolate. The results were used to estimate the effect of a successive extension of organic farming within a county with respect to the average nitrogen losses. The simulation results indicate that significant effects in the reduction of the nitrate losses can only be expected, if a high percentage of the area is converted to organic fanning. Simulations show that for soils with a high vulnerability to leaching, the nitrate concentration of the seepage can not be reduced under the thereshold of 50 mg NO_3 l~(-1) through the assumed crop rotations and management practices. As a result, non arable or non agricultural land is necessary to level out the high concentrations of the arable land. In general, groundwater protection in agriculturally used landscapes has to be realized in a regional context under consideration of site specific conditions.