Effects of clay combined with moisture management on Cd immobilization and fertility index of polluted rice field.

A field-scale trial was conducted to investigate the remediation effects of sepiolite on Cd-polluted paddy soils under different moisture managements, using a series of variables (pH and extractable Cd of soil, plant Cd concentration, plant nutrition and enzyme activity in soil). Results revealed that soil pH increased significantly after sepiolite addition, which promoted the reduction in extractable Cd in soil. After applying 0.5-2.5% sepiolite into soil, due to higher pH and lower TCLP Cd concentration, brown rice Cd reduced by 17-67% under continuous flooding, 14-62% under conventional irrigation, and 13-61% under wetting irrigation (p < 0.05). The activities of phosphatase and invertase increased compared with unamended soil (p < 0.05). The available phosphorus in clay treated soil showed a remarkable raise, with a maximum increase by 14.5%, 16.9% and 18.1% under three moisture managements (p < 0.05). The increasing values of enzyme activity and then plant nutrition in soil revealed that clay application improved the ecological condition of Cd-contaminated paddy soil. The sepiolite application in combination with continuous flooding provided an efficient and safe remediation technology for Cd-polluted rice field.