Foliar Application of Manganese-Zinc Fertilizer Mitigated the Harmful Effects of Cadmium on Wheat and Reduced Human Health Risks

In recent years, the problem of Cd (cadmium) contamination in cultivated soils has grown worse, endangering food security and human health and impeding agricultural sustainability. The application of foliar fertilizer can effectively prevent and control the accumulation of Cd in crops, but the related effects of foliar fertilizer application on the accumulation of Cd in wheat and the risk to human health are not clear. On the Cd-polluted farmland, five foliar fertilizers (multi-element compound fertilizer (Me), manganese-zinc micro-fertilizer (MZ), sodium dihydrogen phosphate (P), water-soluble organic fertilizer (WO) and foliar silicon fertilizer (Si)) and CK (the fresh water was used as the control) were sprayed on wheat at different growth periods (spraying once at the tillering stage and spraying twice at the tillering stage and the booting stage) to investigate the effects of foliar fertilizer on wheat yield and the content of Cd in grains and human health risks. The results showed that the application of five types of foliar fertilizers can lead to an increase in wheat yield, an inhibition of the transfer of cadmium to the edible parts of wheat, and a reduction in the human health risk (THQ). Compared with the CK (the fresh water was used as the control), the impact of Cd stress on the yield of spring wheat was alleviated by the MZ treatment, and the largest yield increase of 24.2% was achieved when MZ was sprayed once. When compared with one application, two applications of foliar fertilizers were shown to effectively reduce the content of Cd in the leaves, glumes, and grains of wheat, while increasing the content of Cd in the roots and stems. Among all foliar fertilizers, the cadmium content in wheat grains was most effectively decreased using MZ2 (spraying twice at the tillering stage and the booting stage), with a reduction of 36.6%. At the same time, the target hazard coefficient (THQ) of foliar spraying was reduced, and using two bouts of foliar fertilizer spraying was more effective in reducing the health risks. In conclusion, MZ fertilizer sprayed twice was a desirable choice for wheat, which was conducive to the safe production of wheat on Cd-contaminated farmland and for contributing to the sustainable development of agriculture.