Introduction: Conventional fertilizers release nutrients rapidly and often fail to synchronize nutrient availability with crop demand, resulting in substantial nutrient losses through leaching, volatilization, and runoff, as well as associated water pollution and greenhouse gas emissions. Traditional controlled-release fertilizers can reduce these losses but generally rely on passive diffusion and fixed release patterns. Biochar-based slow-release fertilizers (BSRFs) offer a more advanced approach because biochar’s porous structure, high surface area, and surface functional groups enable nutrient retention and controlled release while also improving soil properties. This review examines the transition of BSRFs from passive nutrient carriers toward intelligent regulators capable of responding to rhizosphere conditions and coordinating nutrient supply, carbon sequestration, nutrient cycling, and microbial processes.
Key findings: BSRFs can improve nutrient-use efficiency by regulating nutrient release through physical barriers, chemical interactions, and ion exchange, while emerging pH-, moisture-, and temperature-responsive designs offer the potential to better synchronize nutrient supply with crop demand. Beyond nutrient delivery, BSRFs can support nutrient recycling, improve soil health and rhizosphere microbial activity, enhance carbon sequestration, and potentially reduce greenhouse gas emissions. However, long-term field validation, economic and life-cycle assessments, and ecological safety evaluations are still needed before widespread application.
Content adapted from Liang et al. | Figure reproduced from the original article
