Synergistic Effects of Corn Stover Biochar and Bacillus spp. on Reducing Cadmium and Arsenic Accumulation in Rice: Insights from Pot Experiments and Soil Speciation Analysis

This study systematically evaluated the synergistic effects of corn stover biochar (pyrolyzed at 500°C) and heavy metal-resistant Bacillus spp. on cadmium (Cd) and arsenic (As) immobilization in co-contaminated soil and their accumulation in rice plants. A pot experiment was conducted with two contamination levels (H1: Cd 1mg kg−1+As 50mg kg−1;H2:Cd 2mg kg−1+As 100mg kg−1) and four treatments: control (H1/H2),biochar (H1B/H2B), bacteria (H1b/H2b),and biochar+bacteria (H1Bb/H2Bb). The results demonstrated that the combined application of biochar and Bacillus spp. reduced Cd and As concentrations in rice roots and leaves by 35–62%, increased residual fractions of Cd (22%) and As (22%) in soil, and enhanced soil nutrient availability. The synergistic mechanisms involved biochar adsorption, microbial immobilization, and speciation transformation. This study provides a sustainable strategy for mitigating Cd-As co-contamination in agricultural soils.