Soil selenium activator mediates selenium form transformation and affects soil properties and microbial communities

Introduction: Addressing global crop selenium (Se) deficiency requires novel strategies that enhance the bioavailability of native soil Se while minimizing environmental impact. This study introduced a novel organic-inorganic composite activator to achieve this goal. Methods: The composite activator was formulated by combining wood vinegar (WV), biochemical fulvic acid (BFA), and alginic acid (AA) with phosphorus tailings (PT), thereby avoiding the resource consumption and pollution risks associated with external Se input. Through orthogonal experimental design integrated with high-throughput sequencing, correlation analysis, co-occurrence network modeling, and functional prediction, this study systematically elucidated how the composite activator synergistically regulates Se speciation transformation, soil properties, and microbial community structure. Results: The optimized Z8 formulation yielded the following results: (1) Compared to the control (CK) (25.2 μg/kg), the bioavailable Se content under the Z8 treatment (39.2 μg/kg) significantly increased by 56%; and (2) The co-application of PT (containing 8.63% P) and organic acids increased soil available phosphorus (AP) by 21.2% after 60 days. Discussion: In conclusion, this study proposes a sustainable strategy of amending soil with organic acid-activated PT, which synergistically improves soil Se and P fertility while offering a new pathway for the resource utilization of industrial waste.