Nitrogen losses following application of pig slurry to arable land

Emissions of ammonia (NH3) and nitrous oxide (N2O), and nitrate (NO3-) leac hing were measured in two field experiments following application of pig sl urry at rates corresponding to 83-96 kg Nt(4)-N ha(-1) before sowing. In sp ring 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). NH3 emission measurements were made during the first week after application in both experiments. In the spring experiment N2O emissions and NO3- leaching were measured during 6 and 52 weeks after s preading respectively and during 11 and 33 weeks after spreading in the aut umn experiment. In spring, the increased N2O emissions (i.e. control subtra cted) 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 NH4-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. Th e emissions agreed well for (B/H), while (B) resulted in lower emissions co mpared with the smaller chambers. Emissions of NH3 were about one order of magnitude higher. In spring, (B) gave the highest emission, reaching 19.5% of applied NH4-N, whereas (S), and (B/H) gave the lowest emissions, reachin g 1.2 and 3.5% of applied NH4-N, respectively NH3 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 d ifferences. Estimations of indirect N2O emissions due to ammonia deposition and nitrate leaching, suggested that the N2O contribution from NH3 deposit ion was relatively small, while the indirect N2O emissions from NO3- leachi ng were of the same order of magnitude or higher than the direct N2O emissi ons.