Abstract
Soil degradation driven by climate change, deforestation, and unsustainable agriculture threatens global ecological resilience and food security. Current estimates suggest that at least 24% of the world's agricultural land is degraded by overuse, and this proportion is expected to increase in the coming years. This review presents advances in biochar as a soil amendment, emphasising its structural, chemical, and biological impacts on soil fertility. Biochar possesses a highly porous structure with a specific surface area ranging from 10 to 800 m2 per gram, featuring resilient aromatic carbon frameworks and effective nutrient-holding capabilities. Empirical studies reveal that biochar amendments enhance soil porosity by 5–15%, reduce bulk density by 3–12%, and elevate microbial biomass by up to 380% in soils amended with Miscanthus straw biochar. Nutrient dynamics are markedly improved, with nitrogen adsorption capacities reaching 635 mg kg-1 and phosphorus release rates as high as 1664 mg kg-1, depending on feedstock and pyrolysis conditions. However, potential risks, including heavy metal retention (e.g., PAH concentrations up to 3574 μg kg-1 in amended soils) and pH alterations, necessitate judicious management. Collectively, this review positions biochar as a transformative tool for sustainable soil management, contingent upon context-specific application strategies and rigorous monitoring of long-term environmental impacts.