Nitrous oxide production, its source and distribution in urine patches on grassland on peat soil

Urine patches are considered to be important sites for nitrous oxide (N2O) production through nitrification and denitrification due to their high concentration of nitrogen (N). The aim of the present study was to determine the microbial source and size of production of N2O in different zones of a urine patch on grassland on peat soil. Artificial urine was applied in elongated patches of 4.5 m. Four lateral zones were distinguished and sampled for four weeks using an intact soil core incubation method. Incubation of soil cores took place without any additions to the headspace to determine total N2O production, with acetylene addition to determine total denitrification (N2O+N-2), and with methyl fluoride to determine the N2O produced through denitrification. Nitrous oxide production was largest in the centre and decreased towards the edge of the patch. Maximum N2O production was about 50 mg N m(-2) d(-1) and maximum denitrification activity was 70 mg N m(-2) d(-1). Nitrification was the main N2O producing process. Nitrous oxide production through denitrification was only of significance when denitrification activity was high. Total N loss through nitrification and denitrification over 31 days was 4.1 g N per patch which was 2.2% of the total applied urine-N.