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  • Soil Acidity in Tea Regions

    Chemical Characteristics of Tea Growth in Acidic Soils

    The most important chemical characteristic of tea soils is that of soil reaction. There is an upper limit to the pH value of soils in which tea will grow abundantly. The upper pH range in which tea will thrive is between pH 6.0 to 6.5. At the acidic range of the scale there appears to be no limiting value with teas of average quality being reported to grow in soils as low as pH 4.5. It is even possible to grow tea in soils with pH as low as 4.0, the lowest value that soil can be with out free acid.

    Tea is a calcifuge and the preference for acid conditions is associated with low calcium levels in soils. Tea does not grow healthily in alkaline and shows distinct pathological symptoms in basic soils.

    In a normal tea leaf around 0.5% calcium is found, and in leaf dry matter calcium is the most abundant compound with the exception of potash. this calcium is present in the form of calcium oxalate. If a tea plant is deprived of calcium it will not grow successfully. It is therefore considered that a high soil reaction is required for the existence of a calcifuge species such as tea.

    Aluminium in Tea

    Tea is also an aluminium accumulator, certain species have been found to contain extremely high tissue sample levels of aluminium. A typical plant will contain three parts per million of aluminium, whereas certain species of tea contain up to 17,000 parts per million.

    Tea grows on tropical soils that are rich in sesquioxides of iron and aluminium. At ph values of around 6.5 tea shows the adverse symptoms typically associated with unsuitable pH levels, and the aluminium content of the leaves is diminished. It is thought that aluminium may play some regulatory role in the nutrient retention of tea, perhaps as a consequence of toxic ions such as manganese. An alternative is that the nutrient imbalance is due to other ions in the soil being poorly supplied in basic soils.