Influence of area of production, nitrogenous Fertilizer rates and plucking intervals on the \ production of fatty acids in clonal tea '(Camellia sinensis (L.O) Kuntze) leaves

Abstract

Tea, Camellia sinensis, is widely grown in the highlands of Kenya for manufacture of mainly black tea. The most costly inputs in tea cultivation are nitrogenous fertiliser and plucking which are key determinants of yield and quality. The black teas are classified in the tea trade either as plain or flavoury. Flavoury teas are sold for their special aroma normally caused by volatile flavour compounds (VFC). Unsaturated fatty acids break down during tea processing to produce volatile flavour compounds responsible for green grass smell leading to low aroma quality. Previous studies on fatty acid levels and composition were conducted at single locations and results used to draw general agronomic recommendations. Consequently, planting materials have been assumed to replicate their chemical composition in different areas even though factors affecting growth and quality change with environment. Blanket agronomic input, may be producing tea leaves of varying levels of fatty acids especially unsaturated fatty acids resulting in quality differences in different locations. This study aimed at establishing the variation in fatty acid levels of a single tea clone grown under same agronomic inputs and management in different locations. Trials were conducted in plots in five different tea growing locations in Kenya using clone BBK 35 cultivar. Each plot was treated to varying nitrogenous fertiliser rates (0, 75, 150, 225,300 Kg N/ha/year) and plucking rounds (7, 14,21 days). The experiments were in a factorial two design laid out in a randomised complete block. From each location two leaves and a bud . were plucked when plucking intervals coincided. The lipids were extracted using chloroform/methanol (2: 1v/v) mixture, converted into fatty acid methyl esters and quantified through GC-FID analysis and confirmed by analysis of fatty acid authen tic stand a rds under similar conditions. The levels of saturated fatty acids, unsaturated fatty acids, total unsaturated fatty acid and total fatty acid varied significantly (P :s 0.05) with locations and significantly increased (P :s 0.05) with increasing nitrogenous fertiliser rates and longer plucking .intervals. These variations did not follow particular pattern hence significant, (P :s 0.05) interaction effects implying similar agronomic inputs and management in different locations result in different fatty acid levels and may lead to different aroma quality of processed tea. It is necessary to develop region specific nitrogen fertilizer rates and plucking intervals to maximise production of leaves with low levels of unsaturated fatty acids leading to high quality black teas.