Biochar as a Long‐Term Strategy for Rehabilitating Degraded Soils: Multi‐Omics Analysis of Soil–Metabolite–Microbe Interactions in Continuous Soybean Cultivation

Biochar shows significant promise as a soil amendment for enhancing soil fertility and crop yield, but its long‐term influence on soil–metabolite–microbe interactions in continuous soybean systems remains underexplored. In this decade‐long field study, we investigated the effects of different biochar doses (CA: biochar, 12 t·ha−1; CB: biochar, 24 t·ha−1) compared to conventional fertilization (CF) on soil properties, microbial communities, and rhizosphere metabolites. The results showed that biochar demonstrated dose‐dependent improvements in soil properties, including enhanced porosity, pH, organic carbon content, nutrient availability, and enzyme activities, while reducing bulk density. Notably, biochar application restructured microbial communities, with CB treatment enriching beneficial microorganisms (MND1, Ellin6067, Vicinamibacteraceae, and Conocybe) while suppressing potential pathogens (Ceratobasidium and Cyathus). Simultaneously, biochar induced significant modulation of the rhizosphere metabolome, particularly affecting monoterpenoid biosynthesis pathways and plant defense mechanisms, with altered metabolites strongly corresponding to improved soil properties. Multi‐omics network analysis revealed a cascading effect where biochar‐amended soil properties enhanced beneficial metabolites (e.g., (−)‐3‐dehydromangostinic acid and tert‐butyl hydroquinone) while suppressing D‐panthotenate, 4‐Pyridoxate, and (−)‐alpha‐Pinene, resulting in the beneficial microorganism communities (Conocybe and Vicinamibacteraceae) increasing and pathogen (Cyathus) decreasing. Our findings provide novel insights into biochar's long‐term impacts on soil ecological environments and present an innovative strategy for the sustainable restoration of degraded soils under continuous soybean cultivation.