A "win-win" strategy in highly arsenic-contaminated soils: Intercropping cash crops with soil amendments to achieve production while remediating

Arsenic (As) contamination in agricultural soils threatens food safety and public health, driving the need for sustainable and economical remediation solutions that enable safe production. This study developed a "win-win" strategy by combining peanut-sunflower intercropping with low-cost industrial by-product amendments (ferrous sulfate mineral, ilmenite, stone powder) for the synergistic remediation of highly As-contaminated soil (356.62 mg kg⁻¹). A pot experiment with seven treatments was conducted to evaluate the effects on plant growth, As accumulation, soil properties, enzyme activities, and fungal communities. The composite amendment WFS (Weidikang + Ferrous sulfate mineral + Stone powder, 1:2:1) demonstrated the most pronounced benefits. It significantly promoted plant biomass, increasing peanut and sunflower seed biomass by 134.75% and 129.43%, respectively, compared to the intercropping control (CK). Crucially, it reduced As content in peanut roots by 56.20% and effectively maintained As in sunflower seeds below the national food safety limit (0.5 mg kg⁻¹). The amendments facilitated the immobilization of As by transforming it into more stable fractions, notably increasing the amorphous and crystalline Fe/Al oxide-bound As in the rhizosphere. Soil health was concurrently improved, with key enzyme activities like catalase being enhanced by up to 22.06%. Furthermore, the treatment reshaped the soil fungal community structure, enriching beneficial phyla such as Ascomycota and specific genera correlated with As stabilization. This study demonstrates that the novel "immobilizer-intercropping" system enables cost-effective simultaneous remediation of As-contaminated soil and agricultural production, offering practical significance for ensuring food security and the sustainable utilization of marginal lands.