Abstract
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.
Highlights
The in situ application of rice straw enhances CH4 emissions by a large margin
Few studies report the effects of rice straw ex situ application on mitigation of greenhouse gases (GHG) from paddy-upland coexisting system
Wang et al reported that straw retention in late rice season increased much more CH4 emission than in early rice season[25]
Summary
The ex situ application of rice straw in uplands, may mitigate total global warming potential (GWP) of CH4 and N2O emissions from paddy-upland coexisting systems. Straw retention in paddy fields has become prevalent, mainly due to nutrient recycling and forbidden straw burning[5,6,7,8] It provides abundant substrates and exerts priming effect on soil organic matter to release additional substrates for CH4 production, accelerating CH4 emissions by a large margin[7,9,10,11]. The ex situ application of rice straw in upland soils can improve soil organic carbon, nitrogen and microbial biomass[5,8], which may enhance N2O emissions
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