Variation Of Soil Fertility Indicators In Wundanyi Division, Taita District, Kenya

ABSTRACT

The greater Taita community lives in crowded parcels of land that are intensely used to generate household food and family income. Wundanyi division which is the district headquarters is divided into Upper, Medium and Lower zones and has a high population density of 92 persons per Km2. Each household is estimated to generate 95 % of economic income from agriculture. High population, overdependence on agriculture and low income can have adverse effects on soil fertility. The objectives of this study were to determine the levels of local indicators of soil fertility including soil color, ease of tillage, cracks, stoniness, water retention, application of farm inputs, vigour of growth of farm plants, common weeds, farmland and family size, crop yield and adequacy by use of a questionnaire; levels of scientific soil fertility indicators including soil texture, soil organic carbon, pH, total nitrogen, phosphorus and potassium; and their variations across the Upper, Medium and Lower zones of Wundanyi division. Using objective guided sampling, 30 households from the Upper and Medium and 21 from Lower zones were used to determine the percent respondents and variation of local indicators of soil fertility. Ten households from each zone were then involved in farmland soil sampling at 20 cm depth for use in determination of scientific soil fertility indicators. Soil texture was determined by hydrometer method, pH determined by pH meter, organic carbon and phosphorus by colorimetry and potassium by flame photometry. The study established according to percent respondents, that farmlands in the Upper zone had close proportions of grey and red/brown soils, Medium zone had grey soils while the Lower zone had red/brown soils; the soils were highly friable; had water retaining capacity for one week; many farmers applied manure and fertilizer; vigour of plant growth average; soil fertility moderate; farm yield average and farm produce inadequate. The soil color (p < 0.05), ease of tillage (p < 0.05), water retention (p < 0.05), use of farm inputs (p < 0.05), perceived soil fertility (p < 0.05), crop yield (p < 0.05) and adequacy (p < 0.05) varied significantly across the zones. The soil texture was found to be sandy clay loam (SCL) in the Upper and Medium zones and sandy loam (SL) in the Lower zone, with the levels of sand (p < 0.05) and clay (p < 0.05) varying significantly across the zones; the mean pH values were weakly acidic (p < 0.05), adequate and varied significantly across the zones; mean total organic carbon was below 1.33 % (p < 0.05), deficient and significantly varied; mean percent total nitrogen was less than 0.2 % (p < 0.05), deficient and significantly varied; mean total phosphorus ranged between deficient (25.700±9.710 mg/Kg in the Medium zone) to adequate (65.700±17.975 mg/Kg in the Upper zone); while the mean level of potassium was above 93.60 mg/Kg (p < 0.05), adequate and significantly varied across the zones. The study concluded that many of both the local and scientific indicators of soil fertility significantly varied across the Upper, Medium and Lower zones of Wundanyi division and were therefore sensitive indicators of soil fertility; the soil pH was adequate; total organic carbon deficient; total nitrogen deficient; phosphorus ranged between deficient and adequate; while potassium was adequate. The information obtained may be used for customized sensitization of farmers on integrated soil fertility management, as a source of data for objective policy and further research.