Effects of Organic and Organomineral Fertilizers on Soil Physical Properties, Growth and Yield of Tea in Kericho County, Kenya
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Tea production in Kenya provides a livelihood to over six million people and its productivity is influenced by soil fertility. Maximum tea yields are obtained when correct soil nutrients are available in the soil. Long term use of inorganic fertilizer in tea as a mono-crop often results in moribund of tea fields. This study was conducted to evaluate the yields, growth rate and physiological responses of tea clone TRFK 31/8 to three sources of fertilizer sheep manure, enriched sheep manure and inorganic fertilizer NPK (26.5.5). The organic fertilizer and enriched organic fertilizer was applied at four rates of 60, 120, 180 and 240 Kg/ha while NPK 26:5:5 was applied at the rate of 180 Kg /ha and the effects of these applications on the soil physical properties. The trial was done at the Tea Research Institute, Kericho where trials were laid out in Randomized Complete Block Design (RCBD) and replicated three times. The parameters measured included: photosynthetic rate, stomatal conductance, transpiration rate, shoot growth, soil pH, soil hydraulic conductivity, porosity and soil aggregate stability. Collected data was subjected to analysis of variance (P≤0.05) using SAS statistical package version 9.1 and treatments means separated using Fisher’s Least Significant Difference (LSD). The apical shoot growth was significantly highest at a ratio of 4 organic: 1 DAP at a rate of 120 Kg/ha with a peak of 2.93 cm in the wet season at week 4. The highest soil pH was recorded under sheep manure (5.94) at a rate of 240kg/ha while the lowest recorded (3.81) was under the NPK alone at a rate of 180 kg/ha. The hydraulic conductivity increased linearly under the sheep manure, enriched sheep manure at both ratios of 4:1 and 8:1 as the NPK rate increased while the lowest (0.20 m s-1) was recorded at the NPK treatment for the wet and dry seasons. The highest yield was recorded in the enriched sheep manure at a ratio of 8 sheep manure to 1 DAP at 180 Kg/ha with 1019.3 and 917.3 kg/ha for the wet and dry seasons, respectively. The use of enriched sheep manure and DAP at a ratio of 8:1 is recommended and will ensure increased yields and reduced soil degradation in tea production.