The influence of straw returning on N 2 O emissions from a maize-wheat field in the North China Plain.

Crop straw returning has become a prevailing cultivation practice in the vast area of the North China Plain (NCP), while few investigations about its influence on nitrous oxide (N2 O) emission have been conducted. In this study, N2 O emissions from an agricultural field in the NCP with and without straw returning were comparably investigated by using static chambers in two consecutive maize-wheat growing seasons from June 2010 to June 2012. Compared with the NP treatment (compound nitrogen fertilizer only), the cumulative N2 O emission from the SP treatment (compound nitrogen fertilizer plus straw) increased about 150% during the maize season in 2010, but decreased by about 35% during the maize season in 2011. The inconsistent influence of straw returning on N2 O emission from the maize field was ascribed to the evidently different soil moisture between the two years, which was further confirmed by laboratory simulation experiments. About 40% reduction of N2 O emission from the SP treatment during the two winter wheat seasons, which was mainly attributed to anoxic condition induced by rotting the maize straw.