Effects of secondary, micro- and beneficial elements on rice growth and cadmium uptake
中微量元素和有益元素对水稻生长和吸收镉的影响

Effects of secondary, micro- and beneficial elements on rice growth and cadmium (Cd) uptake were investigated in a pot experiment. The results showed that folia application of sodium silicate significantly increased rice grain yield, while calcium carbonate, boric acid and sodium silicate incorporated into soil significantly reduced rice grain yield. The chloride forms of magnesium (Mg), zinc (Zn) and iron (Fe) were more favorable to enhance rice grain yield than the sulfate salts of the three elements, while the sulfate forms of calcium (Ca) and cupper (Cu) just behaved in an opposite manner. Among the three secondary elements of Ca, Mg and sulfur (S), Ca enhanced but Mg and S in particular reduced the concentrations and uptake of Cd in grain. In straw, the concentrations and uptake of Cd were minimized by magnesium chloride and S in particular. It was found that Mg retarded transferring Cd from straw to grain, with magnesium chloride more effective than the magnesium sulfate. Among the micro-elements studied, Zn was most effective in blocking Cd uptake by rice, and followed by Cu, while folia application of the beneficial element of Si as sodium silicate topped the all the treatments in concentrations and uptake of Cd in grain. The treatments of ferrous sulfate, magnesium chloride, cupper chloride, boric acid and borax effectively depressed but the treatments of Zn and folia application of sodium silicate promoted the transfer of Cd from straw to grain, indicating the mechanism of Si blocking Cd uptake by rice was most likely to occur in soil rather than within plant or in the aboveground portions of the plant. It implies that selecting appropriate forms of secondary, micro- and beneficial elements and using proper application methods could effectively reduce Cd uptake by and Cd content in grain in the Cd polluted soil.