Competitive Inhibitory Effect of Calcium Polypeptides on Cd Enrichment of Brassia campestris L.

Most cadmium-polluted farmland and land surrounding mining areas are difficult to repair and control, seriously threatening the food safety of the crops planted in these regions. As an essential element for plant growth, calcium plays an important role in stress-resistance regulation. In this study, Brassia campestris L. was used as the experimental material and polluted soil with cadmium was used as the experimental soil sample, to explore the competition inhibition of calcium polypeptide application on the absorption of Cd2+ by Brassia campestris L. in the growth process, as well as the effect of calcium application on the growth. Results showed that the application of calcium polypeptides significantly promoted the growth of Brassia campestris L. Calcium polypeptides could be used as high-quality fertilizer, alleviating the effect of Cd2+ stress on the growth of Brassia campestris L., and promoting the absorption of K+, Ca2+, and other nutrients by Brassia campestris L. Under different calcium polypeptide application conditions, the effective state of Cd2+ in the soil showed less significant difference, indicating that the calcium polypeptide had weak or limited passivation effects on Cd2+. There was a significantly negative correlation between Cd concentration in Brassia campestris L. and calcium application (r = -0.99, p < 0.01) when calcium polypeptide was over-applied, which indicates that the inhibition effect of Cd2+ absorption on Brassia campestris L. is mainly through competitive inhibition rather than passivation. The results showed that calcium polypeptide has dual functions on the competitive inhibition of heavy metals and a good fertilizer effect, providing a new technology for in situ remediation of heavy-metal pollution, and a new approach for the treatment of cadmium-contaminated farmland and surrounding mining land.