RESPONSE OF DIFFERENT TEA (Camellia sinensis [L.] O. Kuntze) CLONES TO ENVIRONMENTAL FACTORS AT TWO SITES IN KENYA

Abstract

Tea (Camellia sinensis) is a rural-based enterprise and is the leading cash crop in Kenya, making significant contribution to the economy. It is currently the single largest export commodity, accounting for about 26% of the country's total export earnings. In 2012, tea brought in US$ 1.24 billion in foreign exchange earnings. However, tea production is affected by changes in weather, e.g. in 2006, tea yields declined by 5.46% as a result of adverse weather conditions. Studies on effects of weather on tea yields have been conducted in few sites in Kenya. The objective of this study was to determine the effects of environmental factors on yield performance of selected tea genotypes at different agro-ecological sites in Kenya. A split-plot layout for sites was set out in an existing experiment, established in 1998 in RCBD and conducted at two sites differing in altitude and climatic conditions in Kenya: Kangaita (0O30’S and 37O16’E, 2100 m.a.s.l.) in Kirinyaga and Kipkebe (0O17’S and 35O3’E, 1740 m.a.s.l.) in Borabu. Timbilil (0O22'S, 35O21'E, 2200 m.a.s.l.) in Kericho was used as a reference site. The study investigated the genotype versus environment (radiation, temperature, rainfall and location) (G×E) interactions of four tea clones of scientific and commercial importance to the country (AHP SC 31/37, EPK TN14-3, TRFK 301/5 and TRFK 31/8). Initial soil characterization conducted in 2009 showed that texture at Kangaita is sandy loam with a pH of 4.1, while both Kipkebe and Timbilil had clay texture with a pH of 4.6 and 4.0 respectively. Kipkebe soil had higher contents of K, Ca, Mg and Mn while Kipkebe was higher only in P. Kipkebe experienced higher ambient temperatures with mean of 20.0OC compared to Kangaita's 15.5OC. The study recorded a 2OC rise at Kipkebe between 2000 (17.6OC) and 2010 (19.6OC). There was a corresponding rise in ISR by a mean of 0.9 MJm-2 per annum (20.3MJm-2 in 2007, 21.5MJm-2 in 2008 and 21.7MJm-2 in 2009) at Timbilil. Low radiation intensities at Timbilil in 2007 corresponded with low made tea yields at Kangaita (2.1 t ha-1y-1) and Kipkebe (2.6 t ha-1y-1) compared to 2008 (4.4 t ha-1y-1 and 3.2 t ha-1y-1) and 2009 (3.1 t ha-1y-1 and 3.0 t ha-1y-1) respectively. Season 1 (mid-December - March) PAR gave 1,571 mol m-2s-1 at Kangaita and 1,510 mol m-2s-1 for Kipkebe, while 1,304 mol m-2s- 1 and 1,226 mol m-2s-1 was recorded in season 2 (April to August) at Kangaita and Kipkebe respectively. In the third season, PAR was 1,358 mol m-2s-1 at Kangaita and 1,360 mol m-2s-1 at Kipkebe. The study computed PAR to total solar radiation ratio in tea at Kericho to be 0.45. ANOVA showed significant difference in temperature across locations, yield across the three years (F pr. ≤ 0.01) and rainfall between seasons 1 and 2 (F pr. ≤ 0.05). No statistical difference existed in PAR between G×E. Pearson correlation analysis showed a significant strength of association between temperature and location, and rainfall and location (F ratio≤0.01). The study concluded that PAR to total solar radiation in tea over Kericho is 0.45 and that there exists a strong positive correlation between PAR and rainfall and mean made tea yield.