Abstract: The effects of two different extrogenous humic acids on the activity of Cd in clayey farmland were examined by measuring the content of total Cd, DTPA-Cd and MgCl₂-Cd after leaching treatment. After two humic acid treatments, the total content of Cd content in the soil remained unchanged in general, the content of DTPA-Cd decreased from 0.421 mg/kg to 0.313 mg/kg, and the content of MgCl₂-Cd declined from 0.2 mg/kg to 0.169 mg/kg. When leaching time increased from 1 day to 5 days, the total content of Cd also remained unchanged overall, DTPA-Cd decreased from 0.325 mg/kg to 0.265 mg/kg, and MgCl₂-Cd reduced from 0.196 mg/kg to 0.165 mg/kg. In conclusion, both the exogenous humic acids could remove Cd in the soil of clayey farmland.

Key words: farmland soil, humic acid, soil leaching, total Cd, DTPA-Cd, MgCl₂-Cd