Green manuring combined with optimal water management achieves a triple-win for paddy soil quality, rice productivity, and environmental benefits

Green manuring significantly increased rice yield and soil carbon (C) stocks, however, improper farming practices may result in elevated methane (CH₄) emissions. This study investigated the effects of optimizing water management after green manure incorporation on soil quality index (SQI), rice productivity, C Footprint, net ecosystem economic budget (NEEB), and comprehensive evaluation index (CEI) over a 2-year period in a rice-green manure rotation system. A field experiment was conducted including five treatments: winter fallow-rice (WF) and green manure-single rice rotation combined with 0, 5, 10, and 15 days of delayed flooding after green manure incorporation (GM, GM-WM5, GM-WM10, GM-WM15). Compared with WF, green manuring treatments enhanced rice productivity and SQI. Delayed flooding following green manure incorporation achieved CH₄ emission levels equal to or lower than those from WF, with emissions reduced by 37.7 %−76.1 % relative to GM. C Footprint and yield-scaled C Footprint lowered respectively from 43.9 t CO₂-eq ha⁻¹ and 2.7 kg CO₂-eq kg⁻¹ in GM to 9.8 −26.1 t CO₂-eq ha⁻¹ and 0.6 −1.6 kg CO₂-eq kg⁻¹ in delayed flooding managements, while NEEB increased by 1594 −2340 CNY ha⁻¹ compared with GM. CEI showed the trend of WF < GM < GM-WM15 < GM-WM5 < GM-WM10. In conclusion, delayed flooding practice, especially delayed by 10 days after incorporating green manure, achieved a triple-win scenario for soil quality, rice productivity, and environmental benefits compared with traditional water management practices.