Topographic Position and Soil Depth Govern Spatial Variability of Soil Physicochemical Properties and Fertility Status along a Humid Tropical Toposequence in University of Uyo Teaching and Research Farm, Akwa Ibom State Nigeria

Abstract

Topographic position and soil depth are among the principal factors governing soil formation, nutrient redistribution, and spatial variability of soil fertility in tropical landscapes. Understanding their influence on soil physicochemical properties is essential for developing site-specific soil fertility management strategies that enhance sustainable agricultural production. This study evaluated the effects of topographic position and soil depth on selected soil physicochemical properties and fertility status along a humid tropical toposequence within the University of Uyo teaching and research farm, Akwa Ibom State, Southern Nigeria. Soil samples were collected from three topographic positions (upper slope, middle slope and valley bottom) at two depths (0–20 and 20–40 cm), resulting in six composite samples. Standard laboratory procedures were employed to determine particle size distribution, soil pH, electrical conductivity (EC), organic carbon (OC), organic matter (OM), total nitrogen (TN), available phosphorus (Av. P), exchangeable acidity (EA), exchangeable bases (Ca, Mg, Na and K), total exchangeable bases (TEB), effective cation exchange capacity (ECEC), cation exchange capacity (CEC), carbon-to-nitrogen (C:N) ratio, and base saturation (BS) following established analytical protocols.