Effects of phosphorous fertilizers on phytoavailability of cadmium in its contaminated soil and related mechanisms.

To explore an effective measure to ensure the safety of rice quality in cadmium (Cd)-contaminated farmland, a pot culture experiment was conducted to study the effects of of low Cd content (Cd<0. 2 mg∙kg^-1 ) phosphorous fertilizers with an application rate of 0. 10 or 0. 20 g P2O5∙kg^-1 on the phytoavailability of Cd in its contaminated paddy soil, with the related mechanisms discussed. Compared with no phosphorous fertilization, applying 0. 10 P2O5∙kg-1 of calcium magnesium phosphate (CMP) and monopotassium phosphate (MKP) increased soil pH and decreased soil available Cd content significantly, and CMP and calcium superphosphate (CSP) decreased the Cd accumulation in rice significantly. When the application rate was up to 0. 20 g P₂O₅∙kg^-1, calcium hydrogen phosphate (CHP) increased the soil pH and decreased the soil available Cd content significantly, and CMP, MKP, and CHP decreased the DTPA-extractable soil Cd content by 11. 8%, 9. 8%, and 11. 8%, and the NH₄ OAc-extractable soil Cd content by 9.5%, 7.1%, and 7.1%, respectively. All test phosphorous fertilizers could significantly decrease the stem and leaf Cd contents, with a decrement of 24. 9% -50. 8%, and except CHP, the others could significantly decrease the Cd content of brown rice. With the application CMP and CSP, the Cd content of brown rice was close to the National Hygienic Standard for Grains (GB 2715 -2005). Among the test phosphorous fertilizers, those can increase soil pH (CMP, MKP, and CHP) could significantly decrease the availability of soil Cd significantly, and those containing calcium (CMP and CSP) were more effective in decreasing the Cd accumulation in rice. The efficiency of the phosphorous fertilizers was mainly determined by their chemical properties. Alkaline calcium-containing phosphorous fertilizers were more effective in decreasing the Cd absorption and accumulation in rice plant in Cd-contaminated farmland. [ABSTRACT FROM AUTHOR]