Feedstock-dependent mechanisms of biochar on soil aggregation: The overlooked role of manganese oxides

Soil aggregation is a cornerstone process regulating carbon sequestration, nutrient cycling, and erosion resistance in terrestrial systems. The stability of soil aggregates is governed by a complex interplay of organic and inorganic binding agents. While the role of organic matter is well-appreciated, the specific contributions and interactions of redox-sensitive and hydrolyzable metals (e.g., Fe, Al, Mn) as inorganic cements are less constrained, especially under anthropogenic interventions such as biochar amendment. Our study mechanistically investigates how biochar—a carbon-rich soil amendment—modifies the geochemical environment to alter the speciation, distribution, and efficacy of these key binding agents, thereby controlling aggregate formation and stability.