Synergistic effects of microorganisms and passivation materials on the growth and Cd uptake of coriander (Coriandrum sativum L.) in Cd-contaminated soils

Cadmium (Cd) contamination in agricultural soils has become a serious issue owing to its high toxicity to human health via food chain. Appropriate remediation strategies of combining rhizosphere microbes and amendments are strongly advisable for the safe production of crops in contaminated soil to mitigate heavy metal uptake and enhance crop yield. A pot experiment was established to investigate the combined effect of Si-Ca-K-Mg (SCKM) amendment, biochar, arbuscular mycorrhizal fungi (AMF), and indigenous microorganisms on growth, nutrient uptake, and Cd concentration of coriander (Coriandrum sativum L.), as well as soil Cd immobilisation in two acidic soils. The results showed that the application of SCKM amendment and biochar alone significantly reduced Cd concentrations in the shoots and roots of coriander in the two soils. Regardless of amendments, AMF inoc-ulation alone and indigenous microorganisms were more effective at inducing soil alkalinisation and Cd immobilisation in high-Cd soil (1.08 mg/kg). AMF inoculation and SCKM amendment together had a synergistic effect on increasing the biomass and P, K, Mg, and Ca contents of plant tissues in low-Cd soil (0.289 mg/kg). Meanwhile, adding biochar together with AMF inoculation drastically reduced shoot and root Cd concentrations of coriander in low-Cd soil. The synergistic effect of biochar and indigenous microorganisms was significant in high-Cd soil, with a reduction in the concentration of shoot Cd, root Cd, and soil diethylenetriaminepentaacetic acid (DTPA) extractable Cd, respectively. These results suggest that microorganisms in combination with SCKM amendment and biochar application have a potentially additive effect on production and on the reduction in Cd uptake by coriander, as well as mitigating the releases of heavy metals and the associated environmental impact from abandoned mine tailings.

Automated summary

This study demonstrates that the application of microorganisms in combination with SCKM amendment and biochar can effectively reduce cadmium uptake by coriander and enhance crop yield. Under different soil conditions, microbial inoculation and amendment application have a synergistic effect on soil nutrient availability and cadmium immobilization, leading to a significant reduction in soluble cadmium release from the soil.