Mitigating effects of ex situ application of rice straw on CH4 and N2O emissions from paddy-upland coexisting system

摘要

The in situ application of rice straw enhances CH4 emissions by a large margin. The ex situ application of rice straw in uplands, however, may mitigate total global warming potential (GWP) of CH4 and N2O emissions from paddy-upland coexisting systems. To evaluate the efficiency of this practice, two field trials were conducted in rice-rice-fallow and maize-rape cropping systems, respectively. Year-round measurements of CH4 and N2O emissions were conducted to evaluate the system-scaled GWP. The results showed that CH4 accounted for more than 98% of GWP in paddy. Straw removal from paddy decreased 44.7% (302.1?kg ha(-1) yr(-1)) of CH4 emissions and 51.2% (0.31?kg ha(-1) yr(-1)) of N2O emissions, thus decreased 44.8% (7693?kg CO2-eqv ha(-1) yr(-1)) of annual GWP. N2O accounted for almost 100% of GWP in upland. Straw application in upland had insignificant effects on CH4 and N2O emissions, which increased GWP only by 91?kg CO2-eqv ha(-1) yr(-1). So, the transfer of straw from paddy to upland could decrease GWP by 7602?kg CO2-eqv ha(-1) yr(-1). Moreover, straw retention during late rice season contributed to 88.2% of annual GWP increment. It is recommended to transfer early rice straw to upland considering GWP mitigation, nutrient recycling and labor cost.