Climate-Smart Rice Production through Integrated Water and Carbon Management: Methane Mitigation, Biochar and Yield Resilience

Abstract

Rice production occupies a difficult position in climate-smart agriculture because flooded paddy soils support high and stable yields yet create conditions favourable to methane formation, consume substantial irrigation water, and can alter the availability of potentially toxic elements in grain. This critical narrative review evaluates whether methane mitigation, water management, biochar amendment and yield resilience can be integrated into a coherent management strategy rather than treated as separate objectives. Literature published from 2000 to 3 July 2026 was considered, with earlier foundational evidence retained selectively where necessary. The strongest and most consistent evidence supports non-continuous flooding, particularly well-managed alternate wetting and drying (AWD), as the principal near-term field lever for lowering methane emissions and irrigation demand. Across recent meta-analyses, methane reductions are substantial, but nitrous oxide commonly increases, and yield responses depend strongly on drying severity, timing, soil properties, nitrogen supply and cultivar. Mild AWD is therefore better supported than severe drying as a production-compatible mitigation practice. Biochar can improve rice yield, nitrogen-use efficiency and soil carbon status while moderating greenhouse-gas emissions, but average methane mitigation is less consistent than that achieved through water management and is highly contingent on feedstock, pyrolysis conditions, application rate, soil properties and mineral nitrogen input. Direct factorial evidence combining AWD and biochar is still limited, although several multi-year field studies indicate that biochar can partly buffer nutrient losses, contaminant trade-offs and physiological constraints associated with soil drying. Evidence that AWD itself increases yield resilience to drought or heat is mechanistically plausible but remains cultivar- and experiment-specific; it should not yet be equated with proven long-term yield stability under climate extremes. The synthesis supports a hierarchical strategy in which water regime is the primary control, biochar and nitrogen management are context-dependent modifiers, and cultivar choice provides a resilience layer. Future progress requires multi-site factorial trials, explicit life-cycle accounting, multi-contaminant grain-safety assessment and measurement frameworks that verify water status, greenhouse gases and yield stability together.