Tea (Camellia sinensis (L). O Kuntze) Variations in Yields, Yield Components and Leaf Nutrients Responses to Geographical Location and Nitrogen Fertiliser Rates in Kenya

Abstract

Tea provides income and employment to rural populations in many countries. Tea, grown in east and west of the Rift Valley, is the leading export commodity crop in Kenya. Variable responses among genotypes to different environments and fertilizer influence growth, productivity, leaf nutrients, and quality. However, husbandry practices are uniform in all tea growing regions. These recommendations may not be optimum universally. Genotypes planted and management practices may therefore not give desired yields as resource allocation and productivity may not be optimal. Optimized regional fertilizer needs have not accompanied development of region-specific cultivars. Understanding the variations in growth parameters and yields to varying environments may help optimize husbandry practices in different regions. Responses in shoot densities, weights; growth rates and radiation interception of 20 tea clones to ambient temperatures, rainfall, humidity and saturation deficits; the nitrogen use efficiency and responses of clone TRFK 6/8 to nitrogen rates, were studied in different tea growing regions varying in altitude, in two experiments. A genotype x environment clonal evaluation experiment was established in Kangaita, Timbilil and Sotik; fertiliser rate trials were instituted in Timbilil, Changoi and Sotik, each replicated three times in RCBD. Yield and yield components responses to weather parameters varied with genotype, location and season. Shoot growth rates (Timbilil (r = 0.476)) and shoot density (Kangaita (r = 0.652)) significantly (p≤0.05)) correlated with yields. Yield and weather parameters’ contribution to yield changed with locations. Conversion efficiency, it’s constituent components and temperature, combined were related to yields. Altitude significantly determined conversion efficiency, drought reduced yields and rainfall distribution affected seasonal yield distribution. Yield increased with (p≤0.05) nitrogen application, with low responses in Timbilil. Nitrogen application between 75-300Kg N did not significantly change harvestable shoots nitrogen contents though amount of nitrogen removed with crop varied considerably. Nitrogen Use Efficiency decreased with nitrogen rates. Only Ca and Fe leaf contents varied (p≤0.001) with nitrogen rates. All leaf nutrients, except Mn varied significantly with location. No relationships existed between leaf nutrient contents and nitrogen rate at any location. Yield and yield components response to nitrogen rates varied with location and cultivars. Yield components cannot apply as yield indicators in clonal selection, universally. Leaf nutrient content may not indicate plant response to fertilization. Yield and yield components response to nitrogen varied with location. Tea crop response to fertilizer is site specific and universal application of fertilizer may only apply as general guideline but will not optimize production.