The influence of straw returning on N₂O 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 (N₂O) emission have been conducted. In this study, N₂O 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 N₂O 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 N₂O 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 N₂O emission from the SP treatment during the two winter wheat seasons, which was mainly attributed to anoxic condition induced by rotting the maize straw.