Sustainable Rice Production: Evaluating Biochar and Controlled Irrigation for Water Conservation and Greenhouse Gas Emission Mitigation

Abstract

Rice production faces critical challenges from water scarcity and greenhouse gas emissions, particularly in irrigated systems supplying half the global population. While alternate wetting and drying (AWD) irrigation and biochar amendments show individual promise for sustainability, their synergistic potential remains inadequately characterized. This study investigates whether combining these practices simultaneously enhances productivity, conserves water, and mitigates methane emissions in water-limited rice systems. Field experiments across two agroecological zones in Bangladesh (Boro season 2023-24) evaluated ten treatments combining irrigation methods (conventional flooding versus AWD) with biochar doses (0-20 t/ha) and fertilizer inputs. The optimal treatment 10 t/ha biochar with 50% recommended fertilizer under AWD (T8) achieved 6.4 t/ha grain yield (statistically equivalent to conventional management with full fertilizer), while reducing methane emissions by 40% and irrigation water requirements by 64%. Mechanistically, this integration operates through complementary pathways: AWD creates periodic aeration that elevates soil redox potential, disrupting anaerobic methanogenesis, while biochar enhances oxygen diffusion through improved porosity and increases alternative electron acceptors, collectively suppressing methane-producing microorganisms. These synergies improved soil organic carbon, nutrient availability, and water retention, sustaining yields with reduced chemical inputs. Robust treatment effects across contrasting soil types and principal component analysis demonstrate broad applicability. These findings establish that moderate biochar amendment combined with AWD irrigation represents a scalable, climate-smart strategy for sustainable rice intensification, reconciling food security with environmental stewardship in water-stressed regions.