Nitrogen fertilizer alleviates rice yield loss without increasing global warming potential under elevated temperatures.

The adverse impacts of climate warming on rice production have become increasingly evident. In this regard, although our previous field studies enabled us to establish the positive impacts of nitrogen fertilizer on rice grain yield during warming, it remains necessary to clarify whether nitrogen fertilizer under elevated temperatures has any adverse effects on the environment during the grain-filling stage. To further investigate the impacts of nitrogen fertilizer on rice yield and the associated emissions of methane (CH 4) and nitrous oxide (N 2 O) under elevated temperatures, we conducted a 2-year paddy field study using a free-air temperature enhancement (FATE) system. FATE system had a favorable warming effect on the canopy and soil, and greatly decreased grain yield by 23 % on average. In two trial years, elevated temperatures significantly increased in CH 4 emissions by 17.7 kg ha−1and 18.9 kg ha−1, but did not affect N 2 O emissions. Consequently, we detected significant increases in global warming potential (GWP) by 52 % and 19 % and greenhouse gas intensity (GHGI) by 94 % and 56 % under elevated temperatures in 2019 and 2020, respectively. Although nitrogen fertilizer had no significant influence on CH 4 emissions under elevated temperatures, N 2 O emissions significantly increased by 1.5 kg ha−1 and 1.4 kg ha−1 in 2019 and 2020. Nevertheless, nitrogen fertilizer did not affect GWP and significantly decreased GHGI by 10 % under elevated temperatures in 2020. Additionally, elevated temperatures significantly increased the abundance of methanogens (mcrA), ammonia-oxidizing bacteria (AOB), ammonia-oxidizing archaea (AOA), and nitrous oxide reductase (nosZ) genes. Whereas, nitrogen fertilizer significantly increased nitrite reductase (nirS) gene abundance under elevated temperatures. In conclusion, our findings indicated that 60 kg N ha−1 at the heading stage could effectively alleviate the reduction in grain yield attributable to elevated temperatures, without increasing GWP, thereby enhancing the economic and environmental sustainability of paddy field system. • Warming had no impact on N2O emissions but significantly increased CH4 emissions. • Nitrogen fertilizer had no significant impact on CH4 emissions under warming. • Nitrogen fertilizer did not affect global warming potential under warming. [ABSTRACT FROM AUTHOR]