Nitrous oxide emissions following application of residues and fertiliser under zero and conventional tillage

Abstract

Emissions of N O were measured following combined applications of inorganic N fertiliser and crop residues to a silt loam soil in S.E. England, UK. Effects of cultivation technique and residue application on N 2 O emissions were examined over 2 years. N O emissions were increased in the presence of residues and were further increased where NH 4 NO 3 2 fertiliser (200 kg N ha −1 ) was applied. Large fluxes of N treatments after residue and fertiliser application, with 2.5 kg N 2 O-N ha −1 2 2 O were measured from the zero till measured over the first 23 days after application of fertiliser in combination with rye (Secale cereale) residues under zero tillage. CO emissions were larger in the zero till than in the conventional till treatments. A significant tillage/residue interaction was found. Highest emissions were measured from the conventionally tilled bean (Vicia faba)(1.0kgN emitted over 65 days) and zero tilled rye (3.5 kg N 2 O-N ha −1 over 65 days) treatments. This was attributed to rapid release of N following incorporation of bean residues in the conventionally tilled treatments, and availability of readily degradable C from the rye in the presence of anaerobic conditions under the mulch in the zero tilled treatments. Measurement of 15 N-N 2 O emission following application of 15 N-labelled fertiliser to microplots indicated that surface mulching of residues in zero till treatments resulted in a greater proportion of fertiliser N being lost as N 2 O than with incorporation of residues. Combined applications of 15 N fertiliser and bean residues resulted in higher or lower emissions, depending on cultivation technique, when compared with the sum of N O from single applications. Such interactions have important implications for mitigation of N 2 2 2 O-N ha 2 O from agricultural soils. −1