Combined Effects of Straw Returning and Chemical N Fertilization on Greenhouse Gas Emissions and Yield from Paddy Fields in Northwest Hubei Province, China

Abstract

The effects of crop straw returning or chemical N fertilization on greenhouse gas emissions and crop yield have been extensively studied, but their interaction effects remain unclear. So, this study aimed to investigate greenhouse gas emissions and yield from paddy fields as affected by straw returning, chemical N application, and their interactions in the 2017 and 2018 rice-growing seasons in northwest Hubei Province, China. The static chamber-gas chromatography method was used to determine CH4 and N2O fluxes. Straw returning had no significant effect on N2O emissions, but significantly increased CH4 emissions due to increased mcrA abundance and global warming potential (GWP). Chemical N fertilization significantly decreased CH4 emissions by 7.2–18.8% and GWP by 13.5–17.9%, but increased N2O emissions by 72.5–311.1% due to increased abundance of AOA-amoA, AOB-amoA, nirK, and nirS. Both straw returning and chemical N fertilization significantly increased rice yield. Straw returning significantly increased greenhouse gas intensity (GHGI), while N fertilization obviously decreased the GHGI. Moreover, significant interaction effects of straw returning and chemical N fertilization on CH4 emissions, GHGI, and grain yield were observed. The combination of 250 kg N ha−1 of chemical N application and no straw resulted in the lowest GWP, second lowest GHGI and relatively high grain yield among all treatments. In conclusion, 250 kg N ha−1 of chemical N application without straw returning may be an ecological and economic practice for rice production in this study. Nevertheless, ecological-friendly methods of straw returning for sustainable agriculture should be further explored in future studies.