Nitrous oxide emission from soils after incorporating crop residues

Emissions of N₂O were measured from different agricultural systems in SE Scotland. N₂O emissions increased temporarily after fertilization of arable crops, cultivation of bare soil, ploughing up of grassland and incorporation of arable and horticultural crop residues, but the effect was short-lived. Most of the emission occurred during the first two weeks, returning to 'background' levels after 30-40 days. The highest flux was from N-rich lettuce residues, 1100 g N₂O-N ha^-1 being emitted over the first 14 days after incorporation by rotary tillage. The magnitude and pattern of emissions was strongly influenced by rainfall, soil mineral N, cultivation technique and C:N ratio of the residue. Comparatively large emissions were measured after incorporation of material with low C:N ratios. Management practices are recommended that would increase N-use efficiency and reduce N₂O emissions from agricultural soils.