Impact of Seasons on Soil Physico-Chemical Properties and Tea Yields Based on Enriched Sheep Manure Used in Kericho, Kenya

摘要

Tea (Camellia sinensis (L) O. Kuntze) is a perennial crop grown for beverage consumption. Its production is the leading foreign exchange earner in Kenya contributing about 26% foreign exchange and 4% GDP. Nitrogen (N), Phosphorus (P) and potassium (K) are the recommended nutrients for tea production. However, their continuous use has been reported to have negative effect on soil physico-chemical properties and health. Sheep manure has been recommended in tea production for its soil pH buffering effect and increased tea yields. However, effects of sheep manure enriched with inorganic fertilizer on tea soils and yield have not been conclusively investigated. This study was established at KALRO—Tea Research Institute Kericho in Timbilil estate to determine the impact of seasonal variation on soil pysico-chemical properties and yields on enriched sheep manure used. Randomized complete block design (RCBD) experimental design was adopted with 14 treatments replicated thrice. The treatments were: control with no fertilizer use, NPK at 180 Kgs N/ha/yr, sheep manure only and two enriched sheep manure ratios of 4:1 and 8:1 which translates to a mixture of (4:1) 4 parts of sheep manure and 1 part of D.A.P inorganic fertilizer. Same applied to 8:1 ratio, respectively at rates of 60, 120, 180 and 240 Kgs N/ha once per year. Data were subjected to ANOVA in GenStat statistical package and means separated by Duncan’s multiple range tests at P ≤ 0.05 significance level. Results obtained showed that soil physico-chemical properties and tea yields were influenced significantly (P ≤ 0.05) by treatments applied. Soil available water and organic matter were higher on enriched sheep manure 4:1 at 240 rate used while soil porosity and bulk density were not significantly affected. Total N and P, increased with enriched sheep manure ratio of 4:1 at 240 rate while K+, Ca2+, Mg2+, Mn and pH increased with sole application of sheep manure at rate 180 and enriched sheep manure 8:1 at 180 rate. Tea yields increased with enriched sheep manure 4:1 ratios at the rates of 240. The findings recommend enriched sheep manure 4:1 ratio at 240 rates to be adopted by tea farmers within Kericho region. Further studies involving different geographical locations are proposed.