統合的な水・炭素管理による気候スマート水稲生産：メタン削減、バイオ炭、収量レジリエンス

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🔬研究者:水田メタン削減と収量・N2O・汚染物質とのトレードオフを統合的に整理したレビューとして、今後の要因試験設計やライフサイクル評価研究の出発点になる。

🏢実務担当者:AWD導入時の乾燥程度の管理とバイオ炭の併用が、メタン削減と収量安定の両立に有効かを見極める際の実務的指針となる。

🏛政策担当者:J-クレジットやみどり戦略における水稲メタン削減方法論の設計に、AWDの強度管理やバイオ炭の条件依存性を反映させる必要性を示唆する。

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.

• semanticscholar https://journalarja.com/index.php/ARJA/article/download/912/2248first seen 2026-09-12 05:18:23 · last seen 2026-09-22 04:55:04