Effects of different potassium fertilizers on phytoavailability of Pb in red latersol and paddy soil

Effects of four kinds of potassium fertilizer（KH2PO4, K2SO4, KNO3, and KCl）at five levels (K 0，60，140，240，360 mg/kg) on the Pb concentration of rape and relationship between Pb content of paddy soil and red latersol solution with the content of Pb absorpted by rape were examined in pot trial. Results showed that the Pb concentration of soil solution significantly increased with application of KNO3, KCl, and K2SO4. The application of KCl (360 mg/kg) and K2SO4 (240 mg/kg) can increase Pb content of soil solution up to 106.9% and 97.8%, respectively. There were similar effects of three kinds of potassium on paddy soil and increased rate was lower than that of latersol soil. The main reason was that latersol soil had more inconstant charges and smaller CEC than paddy soil. However, Pb content of soil solution was significantly decreased with application rate of KH2PO4, moreover Pb content of rape shoot also decreased in both paddy soil and latersol, and under its highest application rate the decreased rates of Pb concentration in latersol and paddy soil were 45.0% and 63.8%, respectively, compared with the control treatment. In the second season in KH2PO4 treatment, there were positive correlations between Pb absorbed by shoots and roots of rape and Pb content of soil solution.