Effect of Slope Positions on some Properties of Soils under a Tectona grandis Plantation in Minna, Southern Guinea Savanna of Nigeria

Abstract

Topography influence soil erosion and consequently has impact on the properties of soils. This study assessed some properties of basement complex rocks derived soils under a young Teak (Tectona grandis) plantation in Minna, southern Guinea savanna of Nigeria. Three soil profiles sited at the upper, middle and lower slope positions along a toposequence were studied. Soil samples collected from their genetic horizons were analysed. Results have shown that the color of surface horizon differed. The upper had very dark gray (10YR3/1), the middle had very dark brown (10YR2/2) while the lower slope position was characterized by dark yellowish brown (10YR3/4) coloration. Also, the texture of surface horizon differed; the upper slope had sandy clay loam, while the middle and lower slope positions had sandy loam. Soil pH slightly increased down the slope with mean values of 6.7, 6.8 and 7.4 for upper, middle and lower slopes respectively. Surface horizon had the highest soil organic carbon (SOC) content, 15.3, 8.7 and 8.5 g kg-1 and the SOC values decreased down the slope. Total nitrogen (N) was low for all slope positions, with middle slope had the lowest value of 0.1 g kg-1. Available phosphorus (P) was rated low at the upper and middle slopes, 8 mg kg-1, and medium in lower slope, 15 mg kg-1. Calcium (Ca), magnesium (Mg) and sodium (Na) were rated high in all slope positions; potassium (K) was rated low to medium. Effective cation exchange capacity (ECEC) ranged from 6.92 to 20.77 cmol kg-1 and was rated medium to high. Irrespective of slope position, base saturation was rated high with values > 84 %. Despite variation in some properties as influenced by topography, the studied soils have potentials to sustain the current land use type.