Slope-position effects soil hydraulic and physical properties in Northeastern Nigeria

Abstract

Understanding how soil slope positions influence soil hydraulic and physical properties is crucial for sustainable land and water management, particularly in regions vulnerable to erosion and water scarcity. This study evaluated the effects of slope position on soil hydraulic and physical properties in northeastern Nigeria. Nine soil profile pits were made along an upper–middle–lower slope sequence, and soil samples were collected and analyzed for particle size distribution, bulk density (BD), total porosity (TP), saturated hydraulic conductivity (Ksat) and plant-available water content (AWC). Results showed that sand dominated across slope positions, with values decreasing with soil depth, while silt and clay increased downslope. BD values ranged from 1.36 -1.75 g cm⁻³, indicating moderate compaction. Soil TP (32-47%) generally increased with soil depth and was inversely related to BD. Mean Ksat ranged from 2.14 cm/hr (middle slope) to 3.09 cm/hr (upper slope), decreasing consistently with depth. Available water content varied between 0.29 and 0.37 cm³ cm⁻³, increasing with decreasing slope position. These variations suggest that upper slopes favor rapid infiltration and drainage but risk moisture deficits, while middle and lower slopes retain more water but are prone to waterlogging and reduced aeration. The findings highlight the strong topographic control on soil hydrological behavior, emphasizing the need for slope-specific management practices such as organic matter amendment on upper slopes and improved drainage on lower slopes to optimize soil moisture and prevent land degradation.