Soil-land-use-system approach to estimate nitrous oxide emissions from agricultural soils

Emissions of nitrous oxide (N₂O) from agricultural soils contribute significantly to the anthropogenic greenhouse effect. Numerous studies have been conducted during the last three decades to improve the understanding of the processes involved in the release of N₂O from agricultural soils. This enabled the creation of process based models on site and field scale. In addition, a growing number of N₂O emission data are available for different soil-land-use-systems from various climates. The integration of these data in global and national N₂O budgets leads to more improved estimations. Surprisingly, N₂O-emission calculations are rare on regional meso and macro scales. The spatial identification of areas with a high efflux of N₂O on regional meso and macro scales is essential for the implementation of N₂O emission mitigation strategies, thus leading to an increased sustainability of land use. On the basis of the ecosystem approach of Matson and Vitousek (1990), we introduce a new method to estimate regional N₂O emissions from agricultural soils on meso and macro scales. This method considers spatial environmental information from available spatial and statistical data as well as quantitative and qualitative expertise by using the tools of a geographic information system (GIS). An environmental information system (EIS) was built up for a dairy farm region in Southern Germany which includes soil, land use, topography, N₂O emission and farm management data. Using all information in the EIS, it was possible (i) to identify different spatial soil-land-use-systems, (ii) to link emission data and process knowledge to these soil-land-use-systems and (iii) to visualize spatial emission potentials. On this basis, N₂O emission potentials for each of the communities in the study region and the whole region were estimated. The estimated annual N₂O emission potential from agricultural soils for the examined dairy farm region in Southern Germany covering around 775 km² is about 3.0 kg N₂O-N ha^-1.