Biochar-Soil Interfaces: Mechanisms, Temporal Dynamics, and Implications for Soil Structure, Fertility, and Biological Functioning, a Critical Review

Abstract Biochar has emerged as a multifunctional soil amendment with the potential to improve soil quality, enhance ecosystem resilience, and contribute to sustainable land management. However, the high variability of biochar effects across soils, climates, and management systems has limited its predictability and broader application. This review synthesizes current knowledge on biochar–soil interactions through the lens of interfacial science, emphasizing that many of biochar’s agronomic and environmental benefits arise from processes occurring at solid–liquid, solid–solid, and biological interfaces. We examine how biochar properties shaped by feedstock type and pyrolysis conditions govern surface chemistry, charge behavior, porosity, and mineral composition, thereby controlling interactions with nutrients, water, soil minerals, microorganisms, and plant roots. Particular attention is given to biochar-induced modifications of soil structure, aggregation, hydraulic properties, microbial habitats, and rhizosphere processes, as well as the temporal evolution of these interactions during biochar aging. Methodological advances for resolving biochar–soil interfaces are critically discussed, alongside challenges in scaling microscale processes to field and ecosystem responses. This review integrates insights from surface chemistry, soil physics, and soil ecology; it also outlines critical knowledge gaps and research priorities to guide the effective and sustainable application of biochar in climate-resilient soil management.