Seed Inoculation With <scp> <i>Bacillus subtilis</i> </scp> Mitigates Cadmium Stress in Maize by Remodelling the Soil Microbiome and Ionome

ABSTRACT Agricultural soils contamination with cadmium (Cd) is a major driver of land degradation. It threatens soil biological integrity, crop productivity, and food security because of its high toxicity, persistence, and bio accumulative nature. The study aimed at assessing the potential of seed inoculation with Bacillus subtilis as a microbe‐assisted strategy to mitigate Cd‐induced soil degradation and plant stress in maize. The experiment consisted of six different treatments including control (CK), seed inoculation (SI), Cd at 25 mg kg −1 (Cd25), Cd25 with seed inoculation (Cd25SI), Cd at 50 mg kg −1 (Cd50), and Cd50 with seed inoculation (Cd50SI). Cd stress (Cd25 and Cd50) significantly degraded soil biological and chemical properties. Microbial diversity declined by over 60%, soil nutrient availability by up to 20%, and nutrient contents in plant tissues were reduced by 20%–60%. These changes resulted in approximately 50% yield loss while increased Cd accumulation up to 14‐fold and elevated the health risk index (HRI ≥ 1). However, seed inoculation with Bacillus subtilis markedly alleviated these effects. Among all treatments, Cd25SI showed the most promising outcomes, with significant restoration of microbial community structure, increased abundance of beneficial phyla and genera, improved soil nutrient availability by 6%–23%, and reduced Cd bioavailability by 17% compared to Cd25. Cd25SI decreased Cd accumulation by 49%, 42%, and 48% in roots, shoots, and grains, respectively, while enhancing nutrient uptake across growth stages, including nitrogen (15%–65%), phosphorus (20%–70%), calcium (42%–68%), and iron (22%–33%). This treatment further reduced the health risk index by 48% and increased grain yield by 59% compared with Cd25. Overall, these findings demonstrate that Bacillus subtilis seed inoculation effectively mitigates Cd‐induced land degradation by restoring soil microbial function, improving nutrient cycling, reducing Cd transfer to edible tissues, and enhancing crop productivity. This study provides integrated evidence supporting microbe‐assisted remediation as a sustainable strategy for managing Cd‐contaminated agricultural soils.