A Systematic Review on Biochar Application in Agriculture Mechanisms, Benefits, and Future Directions

Biochar, a carbon-rich product derived from the pyrolysis of organic biomass under oxygen-limited conditions, has attracted growing scientific attention as a multifunctional soil amendment with the potential to simultaneously address global food security, soil degradation, and climate change. This systematic review synthesizes evidence from 214 peer-reviewed studies published between 2015 and 2026, following the PRISMA framework, to evaluate biochar's agronomic and environmental applications across diverse soil types and cropping systems.Five core domains were assessed: soil physical improvement, soil chemical enhancement, biological activity stimulation, crop yield response, and carbon sequestration potential. Key findings indicate that biochar application (5–40 t/ha) consistently reduces bulk density by 3–31%, improves water retention by 15–35%, raises soil pH in acidic soils, and increases cation exchange capacity (CEC) by up to 40%. Microbial biomass carbon and arbuscular mycorrhizal fungi colonization were also significantly enhanced, promoting nutrient cycling and biological nitrogen fixation. Meta-analyses of 150+ field trials report mean crop yield increases of 8–15%, with the strongest benefits observed in degraded tropical and subtropical soils. Biochar produced from wood feedstocks at 400–600°C demonstrated the most stable carbon structure, with mean residence times exceeding 500 years, and reduced soil nitrous oxide (N₂O) emissions by 12–54% across multiple cropping systems.Beyond fertility enhancement, biochar demonstrated significant soil remediation potential, reducing plant-available cadmium and lead concentrations by up to 39–44% in contaminated soils. Economic analysis indicates that while production costs remain a barrier, integration with carbon markets and use of locally available waste feedstocks can substantially improve adoption feasibility, particularly for smallholder farmers in low- and middle-income countries.This review proposes an integrated biochar application framework combining soil-type targeting, feedstock selection, and co-application with organic amendments to maximize agronomic and environmental returns. Wider adoption requires continued reduction in production costs, robust carbon market integration, and evidence-based policy support.