PHYSICAL PROPERTIES ALONG TOPOSEQUENCE OF TULA HILL SOILS, KALTUNGO, NORTHERN GUINEA SAVANNAH, NIGERIA

Abstract

The study investigated the spatial variability of key soil physical properties along topo-sequences within four distinct wards (Wange, Baule, Bule-Kaltin, and Yiri) of Tula Hill soils, Gombe State, Nigeria. The region is characterized by sandy soils, hilly topography, and underlying sandstone bedrock. Soil samples were collected from 0-30 cm at four landform positions (crest, shoulder, back slope, and foot slope) across each ward and analyzed for pH, organic carbon (OC), texture (sand, silt, clay), bulk density (BD), aggregate stability (AS), and porosity (PS). Results indicated predominantly sandy textural classes across all locations, confirming the influence of sandstone parent material. Soil pH ranged from moderately acidic to neural. Organic carbon content was generally low (<1%), with some deviations from expected topo-sequence trends, notably higher OC at the crest in Baule and Wange attributed to localized anthropogenic activities (e.g., domestic waste return) and high infiltration due to bedrock. Bulk density remained below critical thresholds (e.g., Baule 1.518–1.573 g/cm³), suggesting no impediment to root growth. Aggregate stability varied significantly by landform, with lower slopes often exhibiting greater stability in Baule (e.g., 26.57% vs. 11.67% at crest). Porosity was generally adequate for aeration and water movement, although some variations against typical down slope increases were noted, potentially due to management practices or unique depositional patterns. The consistent sandy texture and adequate porosity, supported by the highly permeable sandstone bedrock and the presence of springs, suggest high infiltration capacity across the Tula Hills, mitigating surface runoff despite the hilly terrain. This study provides crucial insights into the spatial variability of soil physical properties in response to topography and local management, aiding sustainable agricultural practices and land use planning in similar fragile ecosystems.