磷肥对茶园土壤中镉有效性及其生物累积的影响

通过温室盆栽试验,研究了在不同培养期内(1,2和4个月),不同磷肥(过磷酸钙、磷酸二氢钾、钙镁磷肥)及施磷量(P2O50.2,0.5g·kg-1)对镉污染茶园土壤pH值、土壤有效态镉含量及茶树镉吸收累积量的影响.结果表明:钙镁磷肥的施加可有效提高茶园土壤的pH值,过磷酸钙和磷酸二氢钾对pH值的提高则不明显;过磷酸钙和钙镁磷肥均提高了土壤有效态镉含量,且施磷量不同影响规律亦不同,而磷酸二氢钾对土壤有效态镉含量的影响不显著;茶树累积镉含量为根茎叶,根系对镉的富集能力极强,向茎和叶部位的迁移量较低;钙镁磷肥的施加可显著降低茶树各部位对镉的吸收累积量,0.5g·kg-1施磷水平下效果尤为明显,而过磷酸钙和磷酸二氢钾则使茶树对镉的吸收累积量增加;随着茶树培养时期的延长,土壤pH值和有效态镉含量基本呈下降趋势,根系吸收镉的量逐步升高,而茎和叶中镉的含量有所降低.

Effects of different phosphate fertilizers on the availability and bioaccumulation of cadmium in the tea garden soil

Tea is a widely consumed beverage in the world and is an important economic crop in China. However, in recent years tea gardens were increasingly contaminated by heavy metals such as cadmium (Cd). Root uptake of Cd could contribute to Cd accumulation in tea leaves, thus may impact on human health. To explore an effective measure to ensure the safety of tea quality in Cd contaminated tea garden soil, a pot experiment was conducted to evaluate the effects of phosphate fertilizers with application rates of P2O5 are 0.2 and 0.5 g·kg-1 on the soil pH, bioavailable Cd in soil and Cd absorption and accumulation by tea plants in different culture periods (after cultivation for 1, 2 and 4 months, respectively). Results show that the application of calcium magnesium phosphate (CMP) significantly increases the soil pH values by up to 0.6 units. The improvement of pH values under calcium superphosphate (CSP) and monobasic kalium phosphate (MKP) treatments is not obvious. The applications of CSP and CMP result in an increase of bioavailable Cd concentration, and the influence law is different under different application rates, while the effect of MKP is insignificant. Cd concentration in tissues of tea plant follows the order of root＞stem＞leaf. Most of Cd is fixed by the root of tea plant, and the movement to stem and leaf is very low. CMP significantly decreases Cd absorption and accumulation in the root, stem and leaf of tea plant especially under the application rate of P2O5 0.5 g·kg-1, while the applications of CSP and MKP increase Cd concentrations in all parts of tea plant. As the culture time goes on, soil pH value and bioavailable Cd concentration decrease. Cd adsorption and accumulation by tea root escalate with time going on, and Cd concentrations in stem and leaf after 4 months cultivation are lower than after 1 or 2 months.