Nitrous oxide emissions and denitrification N-losses from agricultural soils in the Bornhoved Lake region: Influence of organic fertilizers and land-use

In situ denitrification N-losses and nitrous oxide emissions were measured over 12 months from sandy soils in Northern Germany. We compared a field in a crop rotation, fertilized mainly with farmyard manure for 30 y (field-FM; N-input: 93 kg N ha^-1 y^-1), with a field under maize monoculture, fertilized with cattle slurry for 30 y (field-CS; N-input: 333 kg N ha^-1 y^-1). A grassland was also investigated for comparison (N-input: 92 kg N ha^-1 y^-1). Annual gaseous N-losses from field-FM were twice those from the other sites (denitrification: 4.9 kg N₂O-N ha^-1 y^-1; nitrous oxide: 5.3 kg N₂O-N ha^-1 y^-1). This reflected the higher microbial biomass content and approximately neutral pH at field-FM. The smaller N-emissions from the grassland were attributed to its relatively dry siting on a slope of 20%. The ratio of denitrification N-loss-to-nitrous oxide emission revealed nitrification as the major nitrous oxide producing process at all sites. Predictors of the temporal changes in N-emissions were nitrate (field-FM), pH (field-CS) and temperature (grassland), indicating the heterogeneity of management.