Effects of Sepiolite Combined with Lime on the Availability of Cadmium and Trace Elements in Rice (Oryza sativa)

A field plot experiment was conducted to investigate the effects of single and combined application of sepiolite and lime on the availability of Cd and trace elements (Fe, Mn, Zn and Cu) in soil and their concentrations in rice grains. Six treatments were set up, i.e., control (CK), low dosage of sepiolite (S1), high dosage of sepiolite (S2), lime (L), low dosage of sepiolite and lime (S1L), and high dosage of sepiolite and lime (S2L). The aim of this study is to provide a reference for rice safe production and nutrition management in acid Cd-contaminated paddy fields. The results show that single application of sepiolite and lime and their combined application significantly increased the pH value, concentration of exchangeable Ca and available Si, but significantly decreased the concentration of available Cd, Fe, Mn, Zn and Cu in the paddy soil. The concentration of CaCl₂-extracted Cd in the soil treated with S2L was significantly reduced by 98.0%. The alone and their combined applications of sepiolite and lime significantly reduced the concentration of Cd, Mn and Cu in rice grains. The S2L decreased the Cd concentration in rice grains and the transfer coefficient (TF _{rice / root}) from root to grain by 62.0% and 48.7%, respectively. Sepiolite and lime reduced soil Cd availability by increasing soil pH and concentration of exchangeable Ca, Mg and available Si. Soil Cd availability and TF _{rice / root} reduction were the main reasons for the decrease of Cd concentration in the rice grains. The combined application of sepiolite and lime is superior to their single application in reducing soil Cd availability and grain Cd concentration. The high amount of sepiolite and lime has the best performance for decrease in soil Cd availability and grain Cd. The available Fe, Zn and Cu enriched in the soil of single and combined application of sepiolite and lime. The available Mn in the soil decreased by 1-2 grades, but concentrations of Mn and Cu in the rice grains were within the normal nutrient range. The combined application of sepiolite and lime reduced the availability of Cd and the level of available Mn, and thus other measures should be combined to increase the level of available Mn.