Enhancing Sulfur Absorption in Soybean Rhizosphere through Arbuscular Mycorrhizal Fungi Inoculation: Implications for Soil Health and Crop Growth

Soybean, a sulfur-loving cash crop, suffers from declining soil sulfur with continuous cropping, hindering its growth and development. Arbuscular mycorrhizal fungi (AMF) form beneficial partnerships with plant roots, aiding in nutrient uptake and promoting plant growth. Recent research has increasingly focused upon AMF's potential to enhance sulfur absorption through increased rhizosphere microbial activity. This study investigated the impact of AMF inoculation on soil organic sulfur mineralization, microbial community composition, and sulfur cycle function genes in the continuous cropping soybean rhizosphere. 16S rRNA sequencing and high-throughput qPCR revealed changes in microbial community composition and the expression of sulfur cycle genes. ICP-MS measured total soil sulfur, and the BaSO4 turbidimetric method determined available sulfur. Following inoculation of continuous cropping soybean soil with AMF, it was observed that OTU1851, OTU1897, OTU2148, OTU3303, and OTU3738, five specific rhizospheric soil sulfur cycling microbial communities, were enriched. And AMF inoculation enhanced sulfur cycle function, the abundance of aspA, soxY and yedZ increased by 143.23 %, 236.04 % and 436.64 %. This led to increased soil arylsulfatase (S-ASF) activity (from 39.17 to 49.82 μg/(mL·h)), available sulfur content (from 12.88 to 17.55 mg/kg), and ultimately, improved soybean sulfur absorption and growth. Therefore, this study holds significant implications for improving available sulfur content and utilization in sulfur-deficient soils. Furthermore, it provides a theoretical basis for using AMF as a biofertilizer to remediate sulfur -deficiency, offering a sustainable and environmentally friendly solution.