Impact of nitrogen and potassium fertiliser application on quality of CTC teas

Tea flush shoots, comprised of three leaves with a bud, were collected from long-term fertiliser trial plots, in four successive plucking rounds after NK manuring, and processed into black tea. The black tea samples were analysed for thearubigins, theaflavins, caffeine, volatile flavour compounds, crude fibre content and water-soluble solids. Results indicated that overall quality of tea was impaired when either nitrogen or potassium was used at high levels. The NK ratio of 1:0.83 appeared to be optimum with respect to quality of made tea as well as for flavour index, particularly when the N dose was 300 (or) 450 kg/ha/year. Amino acid and polyphenol contents of the crop shoots were also higher due to this ratio of NK manuring. A lower polyphenol content was recorded when the plots were supplied with less (or) no nitrogen and potash fertilisers. Positive correlation coefficients were obtained between nitrate reductase (NR) activity of crop shoots and amino acid content.