Nitrification and denitrification derived N2O production from a grassland soil under application of DCD and Actilith F2

The relative contribution of nitrification and denitrification to N2O produ ction was investigated by means of soil incubations with acetylene in a mix ed clover/ryegrass sown sward 5 days after application of a mineral fertili ser (calcium ammonium nitrate) or an organic one (cattle slurry) with and w ithout the addition of the nitrification inhibitor dicyandiamide (DCD) and the commercial slurry additive Actilith-F2. At this time, maximum field N2O emissions were taking place. N2O production by the slurry amended soil was twice as high as that of the mineral amended one. N2O came in a greater pr oportion from nitrification rather than from denitrification in the slurry treatment, while for the mineral fertilisation most N2O came from denitrifi cation. The addition of DCD to slurry produced a decrease in N2O production both from nitrification and denitrification. No reduction in N2O losses wa s observed from addition of DCD to the mineral fertilisation, although DCD resulted effective in reducing the nitrification rate by 53% both in the sl urry and the mineral fertilisation. Actilith F2 induced a high nitrificatio n rate and N2O production from denitrification was reduced while that from nitrification was not.