Microbial inoculations enhance soil aggregation and carbon stabilization via root exudate‐mediated microbial association networks

Whether and how root exudates of Amorpha fruticosa Linn. mediate the positive effects of microbial inoculation (Bacillus thuringiensis NL-11 and Gongronella butleri NL-15) on soil aggregation remains unclear. We conducted two glasshouse experiments and a controlled laboratory incubation experiment to address this knowledge gap. Glasshouse experiments showed that microbial inoculation increased root exudation, changed soil microbial community structure, and enhanced soil aggregation and mean weight diameter (MWD). Microbial inoculation increased the number of nodes and links in bacterial-fungal exudate association networks across soil aggregate sizes. Network properties, including the number of nodes, total links, and microbial-exudate (ME) links, were positively correlated with soil MWD and mineral-associated organic carbon (MAOC). Partial least squares path modeling revealed that inoculation indirectly increases MWD by enhancing MAOC, which subsequently strengthens ME links. The laboratory incubation experiment further showed that a single addition of inoculation-induced exudates did not promote macroaggregate formation but significantly increased MAOC content relative to the control. Inoculation-induced root exudates increased the number of nodes and links in bacterial-fungal association networks across all aggregate sizes, and these network attributes were positively correlated with MAOC. We demonstrate that microbial inoculation enhances soil aggregation and carbon stabilization through root exudate-mediated microbial association networks.