Reducing Excess Nitrogen Through Sustainable Farming Systems in Danish Agricultural Catchments

Nitrogen pollution from livestock manure has emerged as an escalating global concern. Therefore, it is imperative to evaluate the cropping system that will facilitate the optimal utilization of livestock manure while minimizing the environmental impact. In the quest for sustainable agricultural practices, the incorporation of crop residues into soils and intercropping with catch crops, has been identified as promising strategies. Crop residue incorporation is a carbon farming practice that can have significant implications for both soil organic carbon (SOC) and nitrous oxide (N2O) emissions, while catch crops have been an essential tool for reducing nitrogen leaching. This study uses the process-based biogeochemical model LandscapeDNDC to assess the environmental performance of different cropping systems in six representative Danish agricultural catchments (LOOPs). Generally, two fertilization strategies were distinguished: 1) fields receiving only a mixture of pig and cattle slurry (O-fields), and 2) fields (C-fields) receiving mineral fertilizer. We tested eight scenarios of organic or conventional fertilized fields with or without crop residue incorporation and with or without catch crop (C/O ± CR ± CC) The results revealed that organic fields demonstrated not only lower yield-scaled total emissions compared to conventional fields but also shows benefits in terms of net carbon balance. It therefore indicates that organic farming, especially when combined with crop residue and catch crop may lead to reduced nitrogen-related environmental impact while increasing yield.