Sepiolite immobilizes soil Cd to optimize microbial community structure thereby promoting wheat growth and reducing Cd accumulation

Immobilization remediation is a widely employed technology that effectively reduces the migration rate and bioavailability of cadmium (Cd). Sepiolite, a commonly used remediation agent, has proven effective in decreasing soil Cd availability and reducing Cd accumulation in agricultural products. However, further investigation is needed to understand the impact of sepiolite on soil environmental quality and microbial communities. If we add sepiolite to the soil, the soil microbial community structure will be improved, and the abundance of bacteria associated with Cd-fixing and plant growth-promoting will be enhanced, which will significantly immobilize soil Cd thereby enhancing Cd tolerance and reducing Cd uptake in wheat. In this study, field experiments were conducted to assess the effects of sepiolite on wheat yield traits, Cd concentration in various organs, Cd transport and enrichment coefficients in wheat, soil pH and Cd availability, and soil microbial communities. The findings confirm that applying sepiolite in the field enhanced the main yield traits of wheat, significantly elevated soil pH by 0.30-1.04 units, reduced Cd bioavailability by 55.46 % -93.27 % (P < 0.05), and decreased Cd accumulation in wheat by regulating Cd transport and enrichment in different plant organs. The most substantial changes were observed when the sepiolite application rate reached 4500 kg ha^-1. Moreover, the study noted an increase in the relative abundance of dominant species such as Bacteroidota, Acidobacteria, Myxococcota, and Patescibacteria at the phylum level, as well as Sphingomonas at the genus level (3.35 % -39.27 %). This shift indicated an optimized microbial community structure. Furthermore, the relative abundance of soil Cd fixing and promoting bacterial communities, including Massilia, Pseudomonas, and Pantoea, respectively increased by 80.20 %, 64.91 %, and 85.19 % when the usage of sepiolite reaches 4500 kg ha^-1. The research underscores that sepiolite can effectively immobilize Cd in soil, enhance the microbial community structure of Cd-contaminated soil, reduce Cd accumulation in wheat, and promote the safe production of agricultural products.