Synergistic effects of AWD irrigation and potassium application on rice yield and paddy field greenhouse gas emissions

Introduction Irrigation and fertilization are significant for rice productivity and environmental benefits. Evidences on how alternate wetting-drying irrigation (I AWD ) and potassium (K) together influence greenhouse gas emission (GHG) and rice yield still remain largely unknown. Methods A field trial was used to evaluate how K application affect GHG and related microbial functional genes abundance, yield, water use efficiency (WUE), and global warming potential (GWP) under I AWD in 2023 and 2024 in northeast China. Results and discussion The results indicated that I AWD significantly enhanced functional genes ( amoA -AOA, amoA -AOB, nirK and nosZ ) abundances, improved mcrA gene abundance while reducing that of pmoA , and thereby significantly led to rises of 58% (tillering period), 54% (panicle period), and 38% (entire period) in nitrous oxide (N 2 O) emissions and declines of 87% (tillering period), 60% (panicle period), and 76% (entire period) in methane (CH 4 ) emissions, averaged in both years. K application significantly reduced the amoA -AOA, amoA -AOB, nirK , and nosZ genes abundances, enhanced mcrA gene abundance. Compared with K 0 , K 75 and K 150 resulted in 14% and 16% reductions in N 2 O emissions, while K 150 increased CH 4 emissions by 29%. Relative to I CF , I AWD decreased soil NH 4 + concentration and increased soil NO 3 - concentration. Relative to K 0 , K 75 and K 150 increased soil NH 4 + concentration and K application did not significantly alter soil NO 3 - concentration. Under continuous flooding irrigation (I CF ), compared with K 0 , K 150 significantly increased GWP and greenhouse gas intensity (GHGI) by 28% and 15%, while K 0 and K 150 had similar GWP and GHGI under I AWD . Compared with K 0 , K 75 and K 150 significantly boosted rice yield (8% and 11%) and WUE (15% and 18%), respectively. Principal component analysis indicated that I AWD K 75 was recommended considering environmental sustainability and economic benefit in the paddy ecosystem.