Application of different forms of calcium to tea soil to prevent aluminium and fluorine accumulation

Tea Camellia sinensis (L), is a well-known accumulator of aluminium and fluorine from acidic soil. A reduction is desirable as aluminium and fluorine absorbed will leach into the tea liquor through infusion, thus posing a serious threat to the health of consumers. The present study aims to investigate the effects of adding different forms of calcium on Al and F uptake by tea plants, in order to reduce the concentrations of these elements contained in the plants. All true lime materials increased the soil pH and decreased soil extractable Al and F concentrations. There were no (p < 0.05) changes in pH values when CaCl2 was added, and a slight decrease in Al and F concentrations was observed in the treatments with CaSO4. Tea seedlings under the addition of CaSO4 were the tallest and healthiest, followed by CaCl2, CaCO3, Ca(OH)(2) and CaO. Seedlings under large doses of Ca(OH)(2) and CaO were dead. Relative growth rates decreased significantly with the increase of calcium compounds except in CaSO4 treatment. The highest Al concentration was also found in the treatment of 4000 mg CaSO4 kg(-1); it then decreased gradually from 3364 to 933mg Al kg(-1) in leaves. For all treatments in both varieties, F concentrations in leaves were lower than the control (374 mg kg(-1)). Calcium chloride was a suitable agent for reduction of Al and F uptake by tea plants while maintaining a high growth rate of the seedlings. (C) 2004 Society of Chemical Industry.