Ca-Mg Soil Immobilization Combined with Foliar Spraying Si(OH)4 Reduced Cadmium Accumulation in Rice: A Field Study

Minimizing cadmium (Cd) contamination in rice grains is crucial for ensuring food security and promoting sustainable agriculture. Recent studies have investigated soil immobilization and foliar spraying for reduced cadmium accumulation in rice, yielding positive results. This study aimed to confirm the synergistic effects of the co-application of Ca-Mg soil immobilization and foliar spraying Si(OH)4 on Cd uptake and transport in rice through field trials. The results indicated that Ca-Mg decreased the transfer of Cd from soil to root by 33.9% to 55.7%, Si(OH)4 reduced the transfer of Cd from leaf to rachis by 43.8% to 69.7%, and the transfer of Cd from husk to brown rice was lowered by 33.4% to 61.2%. Compared with single application, co-application significantly decreased the bioconcentration factor (BCF)soil-brown rice (p < 0.05), leading to brown rice Cd accumulation conforming to the National Food Safety Standard (<0.20 mg kg−1),with an input–output ratio of 1.47–1.60. Furthermore, Ca-Mg + Si increased rice grain production. Comprehensive analyses using PLS-PM revealed that Ca-Mg and Si(OH)4 directly or indirectly inhibited the translocation of Cd from stems to brown rice, with foliar-sprayed Si(OH)4 significantly contributing to the reduction in Cd content in brown rice. Considering the economic cost and safety of production, Ca-Mg + Si(OH)4 serves as a viable solution that promotes substantial rice growth and enhances yield while additionally inhibiting the accumulation and translocation of Cd in rice.