Contribution of biochar to microbial activities in rice ecosystems growth productivity food security and conservation

Abstract

Rice is the staple food for over half of the global population and faces escalating threats from climate change, soil degradation, and nutrient leaching that undermine long-term production sustainability. Biochar, a carbon-rich product of biomass pyrolysis under oxygen-limited conditions, has emerged as a promising soil amendment for rice ecosystems, improving soil physicochemical properties including porosity, pH, water retention, and nutrient availability and fostering diverse microbial communities that drive nutrient cycling and soil fertility. By enhancing the abundance and activity of nitrogen-fixing bacteria, mycorrhizal fungi, and phosphorus-solubilizing microorganisms, biochar strengthens the biological foundation of rice productivity, supporting improvements in root development, biomass accumulation, and grain yield. Across the reviewed literature, biochar application has been associated with yield increases generally ranging from approximately 8 to 24% at biochar dosage of 5 to 20 t/ha and nitrogen use efficiency improvements of around 10–12%, though these outcomes are highly dependent on biochar feedstock, pyrolysis conditions, application rate, soil type, and rice genotype. Biochar has also demonstrated capacity to reduce nutrient leaching, mitigate drought and salinity stress, and enhance plant resistance to biotic stressors through rhizosphere microbial modifications. Environmentally, biochar contributes to carbon sequestration and has been associated with reductions in methane and nitrous oxide emissions in paddy systems under specific management conditions, though some studies report increased methane emissions, particularly in high organic carbon soils at elevated application rates. Water retention, runoff reduction, and irrigation efficiency improvements represent additional conservation benefits, especially in sandy or degraded paddy soils. However, biochar application is not without risks: negative effects on soil microbial communities, nutrient immobilization in certain soil types, ecotoxicological concerns from poorly produced biochars, and high production costs of $51–386 per tonne present significant barriers to widespread adoption. Realizing biochar’s potential in sustainable rice production requires optimized, site-specific application strategies, cost-effective production technologies, and transdisciplinary collaboration among researchers, farmers, and policymakers. Clinical trial number: Not applicable