Levels of aluminium in green leaf of clonal teas, black tea and black tea liquors, and effects of rates of nitrogen fertilizers on the aluminium black tea contents

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Clonal teas have different aluminium content increasing with age of leaf. Although aluminium and fertilizer nitrogen enhance tea growth and tea yields, respectively, field trials have shown no relationship between total aluminium content in the leaf and clonal tea yields. Higher aluminium concentrations were found in the dust grades of black tea than in the large size grades. However, aluminium levels decreased in the tea liquor from dust grades compared to the large size grades. Only up to 40% of the total aluminium in tea was infused into tea liquors; the amounts infused varied with clones and grading (sorting). Aluminium content of black tea was lowered by increasing rates of nitrogenous fertilizers, more frequent fertilizer application, and application of NPK 20:10:10 as opposed to NPKS 25:5:5:5.