Effect of warming on rice yield and methane emissions in a Chinese tropical double-rice cropping system

Global warming often affects crop yield and greenhouse gas emissions from cropland. However, the effects of warming on rice yield and methane (CH4) emissions from rice paddies in the tropical double-rice cropping systems are still unknown. Therefore, we conducted a field experiment to investigate the effect of warming on rice growth and CH4 emissions in a Chinese tropical double-rice cropping system, using the free air temperature increase facility. The results showed that warming did not affect the rice plant biomass, but significantly reduced the early rice yield by 5.0% and late rice yield by 6.5%. Warming trended to increase CH4 emissions, especially in the flooded stage of early rice seasons. Warming significantly stimulated the abundance of methanogens and methanotrophs, and CH4 production and oxidation potential by 93.3%, 84.3%, 29.3% and 66%, respectively. Warming non-significantly increased the soil dissolved organic carbon concentrations, but significantly reduced the soil NH4+ concentrations. Warming significantly increased yield-scaled CH4 emissions by 7–41%. Our findings suggest that warming may reduce rice yield but increase CH4 emissions from the Chinese tropical double-rice cropping systems and underline the need for agricultural practices of higher rice yield and lower CH4 emissions.