Higher N2O emissions and lower rice yield within double-cropped rice systems of South China under warming

Context: Rice paddies account for approximately 11 % of global agricultural nitrous oxide (N2O) emissions. Climate warming can impact rice plant growth and soil nitrogen (N) cycling, consequently affecting N2O emissions from rice paddies. Research question: The effect of warming on N2O emissions in the double-cropped rice systems of South China remains unclear. Methods: We conducted a field experiment from 2021 to 2022, utilizing the Free-Air Temperature Increase system, to examined the effects of warming on N2O emissions and rice yield within a double-cropped rice system in South China. Results: Warming led to a significant reduction in rice yield by 9 % and aboveground biomass by 4 %, while increasing plant N uptake by 6 % over the two years. Warming significantly stimulated area-scaled N2O emissions by 17 % and yield-scaled N2O emissions by 26 %. Warming significantly increased soil NH4+ content and N mineralization rate by 12 % and 46 %, while reducing soil NO3 - content by 10 %. Warming also significantly stimulated the abundance of nirK, nirS, and nosZ genes involved in denitrification by 20 %, 47 %, and 22 %, respectively. Importance analysis indicated that N2O emissions are primarily driven by N mineralization rate. Conclusions: In the double-cropped rice systems of South China, warming significantly decreased rice yields likely due to heat stress during the reproductive phase, but significantly increased N2O emissions by supplying more N substrate from enhanced N mineralization. Implications: Our study highlights the necessity for agricultural practices to mitigate rice yield loss and N2O emissions within the double-cropped rice systems of South China in the warmer future.