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 (CH4) and nitrous oxide (N2O) 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 CH4 emissions by 17.7 kg ha- 1and 18.9 kg ha-1, but did not affect N2O 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 CH4 emissions under elevated temperatures, N2O 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.

Automated summary

The adverse impacts of climate warming on rice production have been observed. This study examined the effects of nitrogen fertilizer on rice yield and greenhouse gas emissions under elevated temperatures and found that nitrogen fertilizer did not have adverse effects on rice yield and could reduce greenhouse gas emissions.