Effect of seasonal changes in soli moisture, atmospheric humidity, ambient temperature and radiation on shoot water status, growth and yield of four clones of tea, camellia sinensis l

Abstract

Studies on the effects of soil moisture, ambient temperature, atmospheric humidity and radiation on the yields of four commercial Kenyan tea clones were undertaken. The experiment was laid out in an established tea field of clones 6/8, 31/8, S15/10 and 57/15. This was a randomized complete block design replicated three times. The results of the study show that temperature was the main factor which limited the yields of tea at Timbilil Estate, Kericho, Kenya (altitude 2170m a.m.s.l.) during the 24 months of this experiment. So i1 mo isture and high vapour pressure de ficits (VPD) reduced yields in the hot-dry period between January and February. The tea clones gave variable response to these climatic factors. Clone 6/8 was susceptible to low soil moisture and high vapour pressure deficits and consequently it had low shoot water potential, reduced rates of shoot extension, relatively low shoot density, low rates of shoot regeneration and lower yields than clones 31/8, S15/10 and 57/15 between January and February when high VPD and low soil moisture prevailed. There was an increase in yields between October and December of both years when nearly 32% of the total annual yields were recorded. This was .i n response to the favourable env ironmental condi tions. The high air temperatures, low soil moistur-e and low vapour pressure deficits were favourable between October and December. Among the yield components the rates of shoot extension and the number of shoots per un i t area and partly the rates of shoot regeneration varied with changes 1n climate while the mean shoot weights remained largely unchanged. When subjected to the Multiple regression analysis, the combined effect of the yield components, namely, the rates of shoot ext ens ion, the number of shoots per uni t area, the mean shoot weights and the rate of shoots regeneration had highly significant (P=O.Ol) relationship with clonal tea yields, but the effects of individual components was highly variable and did not relate with the yield potentials of clonal tea