Combined Effects of Sulfhydryl-Grafted Palygorskite and Manganese Fertilizers in Reducing Cadmium Accumulation in Wheat

Cadmium (Cd) contamination in alkaline soils poses a significant threat to wheat production and food safety. This study investigated the combined effects of sulfhydryl-grafted palygorskite (SGP) and manganese fertilizers (MnO and MnSO4) on Cd immobilization in soil and its subsequent accumulation in spring wheat via a pot experiment. The results demonstrated that the combined application of SGP and MnSO4 exhibited the highest efficiency, reducing grain Cd concentration by 62.5% compared to the control, which was superior to the single SGP treatment (39.5% reduction). Simultaneously, grain Mn content increased markedly. Soil microbial community analysis confirmed the environmental safety of this strategy, as it showed no substantial shifts in bacterial diversity or community structure. The combined mechanism was attributed to a dual action: SGP served as the primary external immobilization strategy by sequestering Cd in the soil and diminishing its bioavailability, whereas Mn fertilizers, especially MnSO4, functioned as a restrictive mechanism within the plant, competing with Cd for uptake and transport pathways and modifying its translocation, ultimately restricting its allocation to the grain. This study provides a novel, efficient, and environmentally friendly dual strategy of immobilization and antagonism for the safe production of wheat in Cd-contaminated alkaline soil.