Nitrous oxide emissions from maize–wheat field during 4 successive years in the North China Plain

Agricultural soil with fertilization is a main anthropogenic source for atmospheric nitrous oxide (N2O). N2O fluxes from a maize–wheat rotation field in the North China Plain (NCP) were investigated for 4 successive years using the static chamber method. The annual N2O fluxes from the control (without fertilization) and fertilization plots were 1.5 ± 0.2 and 9.4 ± 1.7 kg N ha−1 yr−1 in 2008–2009, 2.0 ± 0.01 and 4.0 ± 0.03 kg N ha−1 yr−1 in 2009–2010, 1.3 ± 0.02 and 5.0 ± 0.3 kg N ha−1 yr−1 in 2010–2011, and 2.7 ± 0.6 and 12.5 ± 0.1 kg N ha−1 yr−1 in 2011–2012, respectively. Annual direct emission factors (EFd's) in the corresponding years were 2.4 ± 0.5%, 0.60 ± 0.01%, 1.1 ± 0.09% and 2.9 ± 0.2%, respectively. Significant linear correlation between fertilized-induced N2O emissions (Y, kg N ha−1) during the periods of 10 days after fertilization and rainfall intensities from 4 days before to 10 days after fertilization (X, mm) in the 4 years was found as Y = 0.048X − 1.1 (N = 4, R2 = 0.99, P < 0.05). Therefore, the remarkable interannual variations of N2O emissions and the EFd's were mainly ascribed to the rainfall.