Impact of magnesium sulphate on biochemical and quality constituents of black tea.

摘要

Effects of soil applications of magnesium sulfate were investigated on biochemical composition of flush shoots and various quality parameters of south Indian black teas. Mg was applied to the soil (200 or 300 kg) with standard NPK fertilizer or with a 50% reduction in K levels. In addition, foliar applications of Mg with micronutrients was also evaluated. Amino acid contents in tea leaves significantly increased after soil application of Mg, but this increase was lower when Mg was applied with 50% K reduction. Foliar application of Mg and micronutrients decreased amino acid contents when compared to standard practice and control values. Externally added Mg increased formation of 2-oxoglutarate and contents of aspartate and alanine. Catechin contents increased after application of 300 kg Mg to soil, but the increases were lower in samples subjected to 50% reduced K application. Similar trends were observed for theaflavin and thearubigin contents of teas prepared from the plants. Flavour scores were improved by Mg treatment, compared to controls and samples fertilized by NPK alone. Mg contents of tea leaves positively correlated with amino acid contents and amino acid transferase enzyme activity. These results confirm previous findings that antagonism exists between the effects of K and Mg in tea fertilizers and that synergism exists between P and Mg.