Nitrous oxide emissions from Chinese maize–wheat rotation systems: A 3-year field measurement

Abstract

Nitrous oxide (N2O) fluxes were measured over a 3-year period (2004–2007) in a long-term experimental field. The objectives of the study were to evaluate the interannual variation of N2O emissions from a maize–wheat rotation, under different fertilizer regimes and to determine the key controlling factors. The study involved four treatments: compost (OM), half compost N plus half inorganic fertilizer-N (HOM), inorganic fertilizer-N (NPK), and control (CK) where no N application. The mean annual N2O emission over a 3-year period was 0.30 ± 0.11 kg N2O–N ha−1 in the CK treatment, but increased to 1.61 ± 0.10 kg N2O–N ha−1 in the HOM treatment, 2.13 ± 0.15 kg N2O–N ha−1 in the OM treatment, and 2.76 ± 0.19 kg N2O–N ha−1 in the NPK treatment. Differences were significant among treatments. The N2O emission factors of the applied OM, NPK and HOM were 0.61 ± 0.02, 0.82 ± 0.10 and 0.44 ± 0.04%, respectively, at a rate of 300 kg N ha−1 year−1, indicating that the combined application of compost with inorganic fertilizer significantly reduced N2O emission. Over a maize–wheat rotation year, more than 65% of the annual N2O emission occurred during the maize growing season. There was a large interannual variation in N2O emission in all treatments, albeit not significant either during the maize growing season or at an inter-year scale. This interannual variation was mainly attributable to differences in soil moisture after basal fertilizer application, and irrigation and/or heavy rainfall events immediately following basal fertilization could induce more N2O production than pre-irrigation before plowing. The HOM treatment had higher N fertilizer use efficiency and lowest yield-scaled N2O emissions compared with the OM and NPK treatments. We therefore argue that the combined application of half compost N plus half fertilizer-N will mitigate N2O emissions from soils in the North China plain.