Assessment of silica-enriched biochar for enhancing soil fertility and mitigating methane emissions in acid-stressed rice fields

Rice cultivation is a source of methane emissions (CH₄), contributing to global warming. Efforts to reduce CH₄ emissions play an important role in sustainable rice production. This study aimed to evaluate the effect of silica enriched biochar on CH₄ emissions, soil chemical properties, and the growth and yield of rice. A field experiment was conducted using a Complete Randomized Block Design (CRBD) with ten treatments comprising combina tions of biochar, silica-enriched biochar, inorganic fertilizers, and control, and each was replicated three times. The MAPAN rice variety was used as the test crop in naturally acidic soils. Scanning Electron Microscopy analysis revealed that silica-enriched biochar contained abundant micropores measuring 9.38 × 5.13 μm. Silica-enriched biochar significantly improved soil chemical properties, including pH, soil organic carbon (SOC), cation exchange capacity (CEC), total nitrogen (TN), total silica (SiO2 ), potential and available phosphorus (P), and potential and available potassium (K), compared to the control (without biochar). Moreover, it effectively reduced CH₄ emis sions. Applying 2.5 t/ha of biochar combined with 50% NPK fertilizer increased pH, potential P, and potential K by 0.52 units, 28.35%, and 27.22%, respectively. Treatment with 2.5 t/ha of biochar, 50% NPK, and 320 kg/ha SiO2 enhanced CEC by 28.66% and TN by 37.14%. Meanwhile, 2.5 t/ha biochar, 100% NPK, and 3 L SiO2 increased SOC by 22.77%. Applying 2.5 t/ha biochar with 3 L SiO2 raised total SiO2 by 22.29% and available P by 11.85%, while biochar at 2.5 t/ha reduced CH₄ emissions by 123.63%. However, none of the treatments significantly af fected rice tiller numbers, plant height, or grain wet weight. These findings demonstrate that silica-enriched bio char can function as a soil amendment to reduce CH₄ emissions and promote climate-resilient and sustainable rice cultivation by simultaneously addressing soil fertility and greenhouse gas emissions