Nitrous oxide emission out of grassland

Grazed grassland which received 295 kg ha(-1) N-fertilizer (NH4NO3), split-applied, was used to measure nitrous oxide emission. The closed box method was used. At the same time, also soil cores were taken for incubation in the presence of acetylene. During 280 days in 1992, a total emission of 8.4 kg N2O-N ha(-1) was found. This was close to 50 % of the total denitrification, which was 18.7 kg (N2O+N2)-N ha(-1) over 280 days. A variability study on N2O emission was carried out on a surface of 1, 100 and 10,000 m(2), respectively. This study confirmed the lognormal distribution of data with variation coefficients of 20 to 25%. It was also found that the effect of application of 200 kg KNO3-N on N2O emission was limited to 2 weeks upon fertilization. It more than doubled the emission rate during this period.