Nitrogen losses following application of pig slurry to arable land

Emissions of ammonia (NH 3 ) and nitrous oxide (N 2 O), and nitrate (NO ‐ 3 ) leaching were measured in two field experiments following application of pig slurry at rates corresponding to 83–96 kg NH 4 ‐N ha ‐1 before sowing. In spring and in autumn 1994, slurry was applied by four methods: trenching (T), shallow injection (S), band spreading immediately followed by harrowing (B/H) and band spreading (B). NH 3 emission measurements were made during the first week after application in both experiments. In the spring experiment N 2 O emissions and NO ‐ 3 leaching were measured during 6 and 52 weeks after spreading respectively, and during 11 and 33 weeks after spreading in the autumn experiment. In spring, the increased N 2 O emissions (i.e. control subtracted) ranged from 0.27% (T) to 0.45% (B/H), and in the autumn study from 0.92% (T) to 1.14% (B/H), of applied NH 4 ‐N, although showing no statistically significant differences. In order to validate the chamber measurements, a ‘megachamber’(21 m 2 ) was used together with an infrared spectrometer. The emissions agreed well for (B/H), while (B) resulted in lower emissions compared with the smaller chambers. Emissions of NH 3 were about one order of magnitude higher. In spring, (B) gave the highest emission, reaching 19.5% of applied NH 4 ‐N, whereas (S), and (B/H) gave the lowest emissions, reaching 1.2 and 3.5% of applied NH 4 ‐N, respectively. NH 3 emissions in autumn were 15–20% lower compared with spring. In spring the increased nitrate leaching ranged from 10.1 (T) to 24.9 kg ha ‐1 (B/H) and from 29.5 (B) to 37.8 kg ha ‐1 (T) in the autumn experiment, showing no statistically significant differences. Estimations of indirect N 2 O emissions due to ammonia deposition and nitrate leaching, suggested that the N 2 O contribution from NH 3 deposition was relatively small, while the indirect N 2 O emissions from NO ‐ 3 leaching were of the same order of magnitude or higher than the direct N 2 O emissions.