Remediation of cadmium-polluted acidic soil with dolomite and calcite to enhance soil health and pak choi growth

Cadmium (Cd) contamination in agricultural soils threatens crop productivity and food safety. This study examined the use of dolomite and calcite amendments in reducing Cd toxicity in pak choi grown in Cd-contaminated soil. Treatments included: control (CK), Calcite 1 (Cal1, 10 g/kg soil), Calcite 2 (Cal2, 20 g/kg soil), Dolomite 1 (Dol1, 10 g/kg soil), and Dolomite 2 (Dol2, 20 g/kg soil). Amendments significantly increased soil pH (P ≤ 0.05), with Cal2 (6.5) and Dol2 (6.2) achieving the highest values at harvest. Cd availability declined (P ≤ 0.05), with Dol2 being the most effective, reducing the toxicity characteristic leaching procedure-extractable Cd from 0.03 to 0.01 mg/kg, NH4NO3-extractable Cd from 0.05 to 0.02 mg/kg, and CaCl2-extractable Cd from 0.40 to 0.01 mg/kg. Dol2 improved biomass and chlorophyll content, while reducing Cd accumulation in shoots by 73.3% and in roots by 70% relative to the control. Antioxidant enzymes were regulated, with decreased peroxidase and superoxide dismutase indicating reduced oxidative stress, while Dol2 maximised urease, catalase, invertase, phosphatase, and phenol oxidase activities. Dissolved organic carbon and microbial biomass carbon also increased, thereby enhancing microbial activity. Dolomite and calcite significantly reduced biological concentration factors, biological accumulation coefficients, and translocation factors, thereby restricting Cd uptake. Overall, dolomite, especially at higher levels, effectively mitigated Cd toxicity, improved plant resilience, and enhanced soil health in contaminated systems.