Nitrous oxide emissions after application of inorganic fertilizer and incorporation of green manure residues

Emissions of N2O were measured after application of NH4NO3 fertilizer and incorporation of winter wheat and rye green manures in two field experiments in southeast England. Incorporation of green manure alone resulted in temporary immobilization of soil N, small N2O emissions and also low availability of N for the following crop. Emissions were increased after application of inorganic fertilizer, and were further increased from integrated management treatments whereby green manure residues were incorporated after fertilizer application. The highest emission was from the incorporated winter wheat green manure plus fertilizer treatment, with 1.5 kg N2O-N ha(-1) (0.6% of N applied) being emitted over the first 55 days after incorporation. This high emission was attributed to the supply of C in the residues providing the energy for denitrification in the presence of large amounts of mineral N and the creation of anaerobic microsites during microbial respiration.