Environmental factors influencing aluminium accumulation in tea (Camellia sinensis L.)

Tea is a major dietary source of aluminium (Al) to humans. There is a need to understand how environmental factors influence Al accumulation in tea leaves in order to devise strategies to lower Al intake from tea. Paired soil and tea shoots were collected from 197 micro-locations across 11 tea plantation estates in Kericho, Kenya. The concentrations of Al and other minerals in tea samples and a range of soil properties were determined. Multiple regression analysis was performed to identify environmental variables that significantly affected tea Al concentration. A comparison was made between washed and unwashed tea samples. Tea samples from a long-term lime and elemental sulphur trial were analysed. Four environmental variables were identified as having a significant positive effect on tea Al concentration, including soil dust contamination represented by tea Ti concentration, the age of plantation, the number of years after pruning and Al saturation in topsoil, whereas two variables had a significant negative effect, including the altitude of plantation and rainfall prior to tea plucking. The effect of soil dust contamination was further verified by a leaf washing experiment. Soil pH was found to have no significant effect on tea Al concentration in both the field survey and the lime and sulphur experiment. Liming would not be an effective method to decrease Al concentration in tea. Avoiding soil dust contamination, plucking tea shoots from plantations at higher altitudes or from younger plantations could lower tea Al concentration.