Inhibitory effect of exogenous mineral elements (Si, P, Zn, Ca, Mn, Se, Fe, S) on rice Cd accumulation and soil Cd bioavailability in Cd-contaminated farmlands: A meta-analysis

A promising strategy for safely remediating Cd-contaminated farmland has been the application of mineral elements, which can reduce Cd accumulation in rice and inhibit its bioavailability in Cd-contaminated farmlands. However, there is still a lack of systematic and quantitative evaluations regarding how different mineral elements affect rice Cd accumulation and soil Cd bioavailability. Here, a meta-analysis was conducted based on 1062 individual observations from 137 published works to explore the effects of Si, P, Zn, Ca, Mn, Se, Fe and S in rice Cd accumulation and soil Cd bioavailability, we aimed to identify key factors that control the reduction of Cd concentration in rice grains. The results showed that the presence of exogenous elements had dramatically reduced rice grains Cd concentrations in the following decreasing order: Fe (43.03%) > P (38.45%) > Si (33.24%) > Ca (31.90%) > Se (29.83%) > Zn (25.95%) > Mn (23.26%) > S (18.78%). The elements of Ca, P and Si had strongly reduced Cd bioavailability in soils by 29.87%, 27.80% and 22.70%, respectively. The effects of these elements on Cd bioavailability appeared to be controlled by soil physio-chemical properties, such as pH, soil organic carbon (SOC) but also water management, application amounts and elemental forms. Overall, this study provides valuable insights into the potential of using exogenous mineral elements to mitigate Cd contamination in rice and farmlands, and facilitates the selection and application of mineral elements for the safe utilization of Cd-contaminated farmlands, taking into account soil properties and other factors that affect their effect.