Sustainable soil management in acidic paddy fields: liming and biochar application reduce greenhouse gas emissions...

Intensive rice cultivation and excessive N fertilization have exacerbated soil acidification in paddy fields, threatening both crop productivity and environmental sustainability. Liming and biochar application are recognized as effective strategies for soil amelioration, yet their interactive effects on greenhouse gas (GHG) emissions and microbial mechanisms remain poorly understood. Here, we conducted a pot experiment to investigate how liming (L0: no liming, L1: medium liming, L2: and high liming) and biochar management (N: no biochar, B: biochar application) synergistically regulate soil N₂O and CH₄ emissions, microbial communities, and rice yields in acidic paddy soil. Liming increased soil N₂O emissions by stimulating ammonia-oxidizing bacteria (AOB) and narG gene abundances. Conversely, biochar application reduced N₂O emissions by 22.4 % through suppressing the availability of mineral N and dissolved organic C (DOC) and promoting nosZ-mediated N₂O reduction, driven by shifts in denitrifier community composition, driven by shifts in denitrifier community composition (e.g., increased Hyphomicrobiales and Caulobacterales). Liming decreased CH₄ emissions by 29.2-52.1 % via limiting C availability (soil organic C and DOC) for methanogens, while biochar application further reduced CH₄ production by downregulating mcrA and upregulating pmoA abundances. Finally, L2B significantly reduced global warming potential by 14.8-76.5 % while increasing rice yields by 10.8-50.7 %, resulting in the lowest GHG intensity. This synergy was attributed to liming-induced pH buffering and biochar-enhanced nutrient retention, jointly optimizing microbial functionality and crop performance. Our findings provide mechanistic insights into how integrated liming and biochar application can reconcile agricultural productivity with climate mitigation, offering a possible strategy for sustainable rice production in acidic paddy soils.