[Effects of adding basalt powder on organic carbon sequestration in red and yellow-brown soils under earthworm inoculation].

The enhanced weathering technology of basalt can promote the fixation of atmospheric carbon dioxide in the form of carbonates/bicarbonates in soils. Earthworms can promote mineral weathering, further contributing to carbon fixation. In this study, we selected red and yellow-brown soil as research subjects and set up three treatments [i.e., control (CK), adding basalt powder (B), and adding basalt powder and inoculating earthworms simu-ltaneously (BE)], and explored the impact and potential mechanisms of earthworm-mediated basalt weathering on Amaranthus tricolor growth, soil respiration, microbial abundance, Ca² and Mg²⁺, soil total organic C, inorganic C and mineral-bound organic C in the field. The results showed that B and BE treatments significantly increased soil pH and Mg²⁺ content of both soils, but significantly increased Ca²⁺ content, soil respiration, aboveground and belowground biomass of A. tricolor only in the red soil. B and BE treatments significantly reduced reactive Fe and Al minerals in both soils and NH₄⁺-N content of the yellow-brown soil, but did not affect NO₃^--N content of both soils. BE treatment significantly increased bacterial abundance of the red soil, but did not affect fungal abundance of both soils. BE treatment significantly increased inorganic C content only in the yellow-brown soil, but significantly reduced Fe/Al bound organic C of the yellow-brown soil, and had no significant effect on total C and organic C of both soils. In addition, BE treatment had no significant effect on soil organic C, inorganic C and Fe/Al bound organic C of both soils compared with B treatment. The random forest model analysis revealed that fungal abundance is the key factor regulating organic carbon accumulation in red soils, while active aluminum minerals and iron-aluminum minerals are respectively identified as the critical determinants controlling the accumulation of organic carbon and iron-aluminum bound organic carbon in yellow-brown soils. Our results indicate that adding basalt powder to soil can significantly promote plant growth in the short term, but did not affect soil organic C formation. The role of earthworms in promoting basalt weathering and soil organic C sequestration in the short term is limited.