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, fer tilized 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 conte nt and approximately neutral pH at field-FM. The smaller N-emissions from t he grassland were attributed to its relatively dry siting on a slope of 20% . The ratio of denitrification N-loss-to-nitrous oxide emission revealed ni trification as the major nitrous oxide producing process at all sites. Pred ictors of the temporal changes in N-emissions were nitrate (field-FM), pH ( field-CS) and temperature (grassland), indicating the heterogeneity of mana gement. (C) 1999 Elsevier Science Ltd. All rights reserved.