Passivating Agents Relieved Cu and Cd Pollution on Maize Growth

Soil heavy metal pollution exists worldwide and strongly affects the crop yield. The passivating agents have been demonstrated to reduce the heavy metal content in plants and relieve the heavy metal stress to plants. This study aimed to compare the alleviation effects of four passivating agents on maize growth under heavy metal pollution. We conducted a comparison experiment in the greenhouse and set up five treatments such as H (heavy metals), HB (heavy metals and 2% biochar), HW (heavy metals and 2% garden waste), HL (heavy metals and 2% lime), and HD (heavy metals and 2% diatomite) and measured the growth index and photosynthetic parameters of maize to compare the passivation effects. Our results showed that the addition of garden waste exhibited the greatest effects on increasing soil NH 4 + , NO 3 − , and available P content. The garden waste, lime, and biochar application all increased the transpiration rate (Tr), net photosynthetic rate (Pn), stomatal conductance (Gs), photochemical quenching (qP), and electron transfer rate (ETR) of maize. Moreover, the garden waste stimulated the plant height, single biomass, and root length of maize. Our study demonstrates that biochar, garden waste, and lime all enhance the photosynthesis and growth of maize and mitigate the heavy metal stress of maize. Therefore, the addition of passivating agents may play an important role in relieving heavy metal pollution in agricultural soils. The study is also potentially beneficial for the remediation of heavy metal–polluted agricultural soils, soil ecological health, and food security.