Mitigating methane emissions and carbon footprint in rice-wheat rotation system by straw centralized returning under rainfed conditions

Direct incorporation of straw into the flooded paddy has been widely confirmed to induce substantial methane (CH 4 ) emissions. Exploring innovative modes of straw return and associated field water management is necessary to mitigate CH 4 emissions without compromising crop yield. Here, a 2-year field experiment was conducted with two wheat straw returning modes [straw evenly-plowed returning (SR) with conventional flooding water management, and straw centralized returning (SCR) under rainfed conditions], to evaluate greenhouse gas (GHG) emissions, crop yields, carbon footprint (CF), and net ecosystem economic benefit (NEEB) in the rice-wheat rotation system. The results showed that the GHG emissions contributed significantly to the total annual carbon source value, accounting for 48.0 % and 43.0 % in SR and SCR, respectively. The mean CF in SCR was 6760 kg CO 2 -eq ha –1 , which was 17.6 % lower than that in SR, primarily due to the significantly lower CH 4 (by 27.5 %) during the rice seasons. Lower soil water contents might partly regulate the CH 4 emissions by decreasing DOC contents and increasing the soil Eh, leading to a lower CH 4 production potential (decreased by 44.3–45.8 %) and production/oxidation potential ratio in SCR. Annually, the total yields of rice and wheat were 9.53 t ha –1 and 9.38 t ha –1 in SR and SCR, respectively. However, the irrigation electricity consumption and CF costs were lower in SCR, resulting in an increased NEEB of 179 CNY ha –1 relative to SR. The findings suggest that straw centralized returning under rainfed conditions in the rice season could reduce both CH 4 emissions and carbon footprint while sustaining food security and economic benefit in the rice-wheat rotation system. • Straw centralized returning (SCR) reduced CH 4 emissions in the rice season by 27.5 %. • SCR reduced the carbon footprint by 1444 kg CO 2 -eq ha –1 yr –1 . • The annual grain yields of two straw return modes were 9.38–9.53 t ha –1 . • SCR increased the net ecosystem economic benefit by 179 CNY ha –1 .