Reduced nitrogen fertilizer application mitigated CH4 fluxes from rice paddies under an elevated CO2 concentration

Purpose Nitrogen (N) fertilizer is a critical factor in achieving high rice yields, but it can also contribute to increased CH(4 )emissions from rice paddies. Determining how to utilize N fertilizer to effectively balance the contradiction between methane (CH4) emissions and rice yield remains an urgent need in the face of unstoppable climate change. Materials and methods In this study, the response of CH4 fluxes in rice paddies to elevated carbon dioxide (CO2) concentration (e[CO2]) and reduced N application were investigated. The rice biomass and yield, CH4 fluxes, soil properties, and methanogenic characteristics were observed in control (CK) (ambient CO2 concentration + application of 250 kg N ha(-1) urea), C+ (e[CO2] by 200 ppm + 250 kg N ha(-1) urea), N- (ambient CO2 concentration + 150 kg N ha(-1) urea), and C+N- (e[CO2] by 200 ppm + 150 kg N ha(-1) urea) treatments. Results and discussion The results revealed that the C+ and C+N- treatments significantly increased the CH(4 )emissions/yield by 20.0% and 18.8%, respectively, while the N- treatment significantly suppressed the CH4 emissions/yield by 13.3% compared to CK. The N- treatment weakened the promotion effect of C(+)on the rice total biomass, the soil dissolved organic carbon (DOC) concentration and invertase activity, and the CH4 emissions/yield. Moreover, the C+N- treatment significantly reduced the soil DOC concentration and the abundance of the mcrA gene in the grain-filling stage compared to C+. Conclusions Overall, under climate change conditions, N reduction can mitigate CH4 fluxes from rice paddies by affecting rice growth, soil methanogenic characteristics, and the C substrate.