Exogenous silicon has been shown to enhance plant growth and alleviate heavy metals toxicity, but the regulation mechanism of silicon on cadmium migration and transformation in the soil-rice system is still unclear, which is worth further study. In this study, a pot experiment was carried out to explore the influence of different doses (0, 1 and 5%) of mineral silicon on soil properties, nutrient availability, rice growth, soil enzyme activities, Cd bioavailability, and uptake and accumulation of Cd in high-accumulating (H) and low-accumulating (L) rice cultivars grown in contaminated soils. Results showed that mineral-Si treatment could increase the total biomass and grain yield, with an increased rate of 17.7-27.3% and 14.7-19.1% for H; while 26.2-33.4% and 21.3-30.3% for L. Compared with non-mineral-Si treatment, the soil EX-Cd decreased by 3.9-13.3% (H) and 2.3-10.7% (L). Additionally, the Cd content in rice grain was significantly declined by 29.5-31.3% (H) and 34.9-35.2% (L). Mineral-Si enhanced urease, sucrase, and neutral phosphatase activities in both cultivars, but suppressed catalase activity in H. A selective change in bacterial community structure was observed under mineral-Si treatment, however, the bacterial community remained stable, suggesting that the mineral-Si had no adverse effect on the microbial community. The positive response of soil enzymes activities, rice growth and the overall stabilization of microbial environment for mineral-Si addition to the Cd contaminated soils indicated that mineral-Si could mitigate the risk of Cd and well maintain the soil health, proving it to be eco-friendly and low-cost amendment for soils remediation.
Keywords: Accumulation and translocation; Cadmium; Mineral silicon; Rice (Oryza sativa L.); Soil health.
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