The Effects of Calcium and Sulfur Fertilizers Accompanied by Different Side Elements on the Growth and Cd Uptake of Spinacia oleracea Grown in Cd-Contaminated Alkaline Soil

The detoxification of crops grown in Cadmium (Cd)-contaminated acid soil has been widely studied, but for contaminated alkaline soil, there is still inadequate research or information. In order to investigate the effects of calcium and sulfur fertilizers, accompanied by different side elements, on the growth and Cd uptake of Spinacia oleracea grown in Cd-contaminated alkaline soil, the plants were subjected to five treatments, including calcium silicate (Ca-Si), calcium biphosphate (Ca-P), magnesium sulfate (S-Mg), ferric sulfate (S-Fe), and zinc sulfate (S-Zn), and a control group. The results showed that the S-Fe achieved the highest shoot fresh mass and dry mass and the highest shoot Cd concentration and accumulation, which were 30%, 68%, 4.6%, and 73% higher than the control group, respectively. The Ca-Si, Ca-P, S-Mg, and S-Zn reduced the root Cd concentration by 18%, 42%, 7%, and 49%, respectively, and reduced the shoot Cd concentration by 25%, 36%, 15%, and 27%, respectively, as compared to the control. S-Fe increases plant N uptake and photosynthesis, which is beneficial to biomass accumulation. Ca-P improves soil and plant P nutrition status, as well as plant K and Ca status, and helps alleviate plant Cd stress. Overall, calcium fertilizers accompanied by phosphorus have the potential to reduce plant Cd contamination risk, while sulfur fertilizers accompanied by iron show potential for enhancing Cd extraction.