Spatial Variation of Soil Nutrient Stocks in Semi-Arid Tharaka Districts of Eastern Kenya

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Date
2012
Authors
J. N. Gitari
Amboga,S.
Ouma,J.
Gitunu,A. M.
Muriithi,C.
Kanga,L.
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Abstract
This study was conducted in November 20 lion a sample of 96 farm fields located in 12 different smallholder farms. The study sites were in Nkarini, Ntugi, Nkondi and Thiiti locations of the Tharaka North and Tharaka South districts of eastern Kenya. In each of the fields sampled, soils were collected from 9 different spots at a depth of 0-15 cm. The soils were analyzed for soil chemical properties that included soil reaction (PH), exchangeable bases (Ca++ and Mg++), extractable phosphorus, organic carbon (OC), total nitrogen and micronutrients (Zn++, Cu++, Fe+++ and Mn++). There were significant statistical differences among soil fertility categories, using parametric techniques (ANOVA) for key soil properties (P<0.05), implying that the soils must have belonged to different populations and that there was a qualitative difference in the soils. A close scrutiny of soils analyzed indicated that important nutrient stocks such as nitrogen and zinc now fall below the critical levels «0.2% Nand <5.0 ppm Zn) while phosphorus and potassium were frequently deficient in many farm fields of Tharaka, probably attributable to a situation of continuous removal through crop products and residues coupled with intensified grazing of the fields, without adequate nutrient replenishment.
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East African Agricultural And Forestry Journal, 74 (No 4), p. 203-209