Influence of topography on soil morphological and physical properties on the newer basalts of the Jos Plateau, Nigeria

Abstract

This study evaluated changes in soil morphological and physical properties associated with slope positions along a toposequence on newer basalts of the Jos Plateau. Eight pedons were sunk along a toposequence on the crest, upper, middle and lower slope positions. The pedons were described according to their genetic properties; soil samples for laboratory analysis were taken from each pedogenic horizons. Results from the study showed that the pedons were well developed, with depths slightly exceeding 180cm at the crest and middle slope position. The thickness of the surface horizons varied with slope positions, with thicker horizons (25 -30cm) obtained at the middle and lower slope positions. The least developed pedons were those at the upper slope position. The soil texture varied from sandy clay loam (upper slope) to clay at the crest and lower slope position. Higher gravel content (57 – 70%) was obtained at the upper slope. Sand content followed similar pattern to that of the gravel. Clay content increased with profile depth, except at the upper slope where pedons were not well developed. Soils at the various slope positions were not highly weathered as shown by low silt to clay ratio values (0.36 – 0.96). Bulk density values were < 1 for surface horizons and slightly increased with profile depths. Generally bulk and particle density values did not differ with slope positions.