Continuous milk vetch amendment in rice-fallow rotation improves soil fertility and maintains rice yield without increasing CH4 emissions: Evidence from a long-term experiment

Catch crop (green manure) planting is considered an efficient strategy to improve soil fertility in agro-ecosystems. Methane (CH 4 ) emissions from paddies subjected continuous green manure amendment though a topic that remains unexplored. To clarify the impact of on rice yield and CH emissions, long-term trial (established 2003, Yixing, China) was designed with field observations conducted between 2019 2020. Two crops (milk vetch, ryegrass) were selected as catch fallow control, all trialed at two N application rates i) low dosage deriving optimum effect yield-N fertilizer (LN, 200 kg ha -1 ), ii) higher dose empirical farmer's (HN, 270 ). The results showed notably increased organic carbon (SOC) compared while HN significantly dissolved nitrogen LN. among treatments remained similar, ranging 8.6 t 9.4 (two years’ average). related manure, unaffected by rate. Ryegrass after 18 years remarkably stimulated other treatments, difference milk vetch-amended found insignificant. mcr A gene abundance becoming highest under HN. Methanogens SOC content main factors affecting ryegrass addition. Moreover, emission intensity aligned mainly due similar yield. Overall, vetch recommended increases maintains without increasing emissions. • Continuous could increase (SOC). Grain N-application Green factor mediating paddy emission. enhanced contrary amendments. key amended plots.