Effects of Phosphate Fertilizers on Bioavailable Lead in Tea Garden Soil and Lead Absorption and Accumulation by Tea Plants

Tea is a widely consumed beverage in the world and an important economic crop in China. However in recent years tea gardens were increasingly contaminated by heavy metals such as lead (Pb). Root uptake of Pb could contribute significantly to Pb accumulation in tea leaves due to the strong acidity of tea garden soils. To reduce the Pb bioavailability and absorption by tea plants, a pot experiment was conducted to evaluate the effects of 3 phosphate fertilizers separately with a normal application rate in the field of 0.2 g (P2O5) ·kg-1soil and a high application rate of 0.5 g (P2O5) ·kg-1soil on bioavailable Pb in tea garden soil and Pb absorption and accumulation by tea plants. Results showed that application of calcium magnesium phosphate significantly increased soil pH by up to 0.6 units from 3.50 to 4.13. Phosphate fertilizers resulted in an increase of bioavailable Pb concentration in tea garden soil under our experimental conditions. Pb concentration in tissues of the tea plants under different phosphate fertilizer treatments followed the order of root>stem>leaf. Calcium magnesium phosphate with a high application rate of 0.5 g P2O5·kg-1soil decreased Pb concentrations of roots, stems and leaves of tea plants significantly. For one phosphate fertilizer, Pb absorption in tea plants under high application rate was much lower than it under normal application.