Artificial humic acid (A-HA), which is synthesized from agricultural wastes and has high similarity to a natural humic substance (HS) extracted from soil, has been proven by our group to have potential for biological carbon sequestration in black soils. However, the mechanism involves in the application of A-HA on soil aggregation processes resulting from microbial activity stimulation and modifications to microbial communities remains unclear. This study investigates the correlation between the formation and stability of soil aggregates and fungal communities with various amounts of A-HA added to the rhizosphere and non-rhizosphere soil. A-HA can increase the total organic carbon (TOC) and dissolved organic carbon (DOC) concentrations in soil, promoting macroaggregate formation and increasing the mean weight diameter (MWD). In addition, soil aggregate binding agents such as polysaccharides, protein, extracellular polymeric substances (EPS), and glomalin-related soil protein (GRSP) are significantly increased by the addition of A-HA. A-HA can drive microaggregate to assemble into macroaggregate by increasing the abundance of beneficial fungi (e.g., Trichoderma and Mortierella). The co-occurrence network supports that A-HA shifted the key species and increased interactions of fungal taxa. This study will lay a solid foundation for sustainable agricultural development of A-HA application for soil fertility restoration in the future.
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