Assessment of Soil Degradation under Different Toposequence Units and Cropping Systems in the Southern Guinea Savanna of Nigeria

Abstract

The study was carried out to assess the degree of soil degradation at different sampling seasons, toposequence units and different cropping systems at JoSTUM and Wurukum in Makurdi, 2023. Soil samples were taken at 0–15 and 15–30 cm depths at the toposequence units under different crop types (maize, cassava and cowpea) and two seasons (June/July and December/January) for routine analysis. The experimental design was a 2x3x3 factorial experiment laid out in a Randomized Complete Block Design replicated three times. Data analysis was done using Genstat Statistical software, and significant means were separated using Fisher’s least significant difference at 5% level of probability. Soil degradation assessment was done using standard indicators and criteria. Soils of the two locations were loamy sand in texture. Soil bulk density ranged from 1.46 to 1.63 gcm^-3. Total porosity ranged from 47.99 to 55.80 % while Soil Moisture Content and Saturated hydraulic conductivity were not significantly different between locations. Soil pH was slightly to moderately acidic, total nitrogen was low across the two locations, sampling seasons and toposequence units. Cation exchange capacity did not differ significantly. The soils of JoSTUM were more degraded compared with the soils of Wurukum. Likewise, dry-season sampling indicated higher degradation than wet-season sampling. Degradation decreased progressively with slope position, being most severe at the upper slope, followed by middle slope, and least at the toe slope. The study revealed that degradation was more pronounced in upper slope positions, during the dry season, and under cassava cultivation, indicating the need for improved soil conservation and nutrient restoration practices.