Effect of water and fertilization management on Cd immobilization and bioavailability in Cd-polluted paddy soil

The field trial was conducted to investigate remediation effects of two alkaline fertilizers and three water management techniques on Cd contaminated paddy soil. The results revealed downward trend of soil pH and EC during growth period of rice. The treatment of organic fertilizer has indicated high pH and organic matter than treatment of calcium magnesium phosphate fertilizer. The integrated effect of organic fertilizer and continuous flooding (COF) has significantly (p < 0.05) reduced soil Eh to -180 mv at booting stage. The exchangeable Cd of soil decreased with growth of rice in all treatments. The continuous flooding has showed lowest content of soil exchangeable Cd at every stage of rice growth than other treatments. The organic fertilizer, calcium magnesium and phosphorus have promoted growth of rice. The treatments of continuous flooding were most effective in reducing Cd content in rice grain by 12.6-51.9%. The treatments of continuous flooding have lowest TF_husk-rice, and TF_shoot-husk. The BCF of continuous flooding was 0.13, 0.35 and 0.13. According to Pearson correlation coefficients, soil exchangeable Cd concentration has significantly (P < 0.05) negative correlation with soil pH and EC, but has significantly (P < 0.05) positive correlation with soil Eh. The Cd concentration of rice grain has significantly (P < 0.05) positive correlation with Cd of leaf, and negative correlation with Cd of husk. It is concluded that organic fertilizer combined with continuous flooding was most effective management strategy for Cd remediation in paddy soil.