Variations In Yields And Yield Components With Geographical Location And Response Of Clonal Tea (Camellia Sinensis) To Nitrogenous 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 regionspecific

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.