Ecohydrologic Effects of Shade Trees Spacing on Soil Characteristics Affecting Tea Yields and Quality: a Case Study of Moniere Estate in Kipkebe of Sotik Sub-county

Abstract

Shades are used to modify the micro-climatic and environmental conditions which in turn affect soil hydrologic attributes such as moisture content, hydraulic conductivity, porosity and the rate infiltration that determine growth and development of tea. They are also a key source of organic matter which affects soil stability and health that determines all the other soil hydrological properties. Their use and subsequent effects on soil hydrologic properties and resultant impacts on tea yield and quality in tea farms are wide spread in Kenya. The study addressed the issue of deterioration of soil hydrologic characteristics due to soil pollution and unsustainable agricultural practices that causes soil compaction, loss of pore space and structure which negatively impacts tea yield and quality in tea farms. The main focus of the study was to identify and characterize shade spacing ecohydrologic effects on soil properties and their resultant effects on tea production. Using an experimental physical model, the ecohydrologic effects of shade trees on soil hydrological characteristics affecting tea production were investigated using data on soil moisture content, hydraulic conductivity, soil porosity tea yield and tea quality collected from nine experimental fields with three varying shade tree spacing of 6m by 6m, 8m by 8m and the control. The soil hydrologic properties were derived from three soil samples of 0-20cm, 20-40 cm and 40-60cm depths respectively from each experimental field at each shade tree spacing characteristic. Tea yield and tea quality were derived from tea leaves harvest associated with each shade tree spacing characteristic. The study employed random sampling technique of grid each marked with random numbers to ensure consistency in sample collection of soil and tea leaves samples. The soil hydrologic properties of the samples soils were determined both in the field for soil infiltration using infiltrometer gadgets and in the soil laboratory determining soil porosity by water absorption method, hydraulic conductivity by constant head method and moisture content by gravimetric method. Tea yields and tea quality were also determined in the laboratory using the ISO Procedure for total polyphenol content, thearubigins by Roberts and Smith method and Flavognost method for theaflavins. To associate and measure differences between shade trees spacing, soil hydrologic characteristics, tea yield and tea quality statistical techniques of Pearson’s correlation, ANOVA and PCA were used in which significance tests in all cases were at α 0.05. Results obtained showed that the soil hydrological characteristics were affected or varied significantly (P≤0.05) with shade trees spacing while all their interaction with depth and seasons were insignificant except hydraulic conductivity that varied significantly (P≤0.01) in relation to seasons. Tea yield and tea quality were insignificant at (P≤0.05) alongside all other interactions in relation to shade trees spacing. The correlation between soil infiltration rate and porosity, hydraulic conductivity and the total polyphenol content were significant (P≤0.05) while all the others were insignificant. This study found that both the 6m by 6m and 8m by 8m shade trees spacing showed similar results hence they can be used in tea farms in similar hydrometeorological areas in Kenya for high production of tea and environmental conservation