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 kgNha(-1) yr(-1) in 2008-2009, 2.0 +/- 0.01 and 4.0 +/- 0.03 kgNha(-1) yr(-1) in 2009-2010, 1.3 +/- 0.02 and 5.0 +/- 0.3 kgNha(-1) yr(-1) in 2010-2011, and 2.7 +/- 0.6 and 12.5 +/- 0.1 kgNha(-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, kgNha(-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, R-2 = 0.99, P < 0.05). Therefore, the remarkable interannual variations of N2O emissions and the EFd's were mainly ascribed to the rainfall.