Assessment of Physicochemical Properties of Soils Underlain by Different Geological Formations in Enugu and Anambra States, Southeastern Nigeria

Aims: To assess the influence of different geological formations on the physicochemical properties of soils in Enugu and Anambra States, southeastern Nigeria. Study Design: A field-based comparative study employing laboratory analysis and statistical evaluation of soil physicochemical properties across multiple geological formations. Place of Study: The study was conducted in selected locations within Enugu and Anambra States, southeastern Nigeria. Methodology: Soils developed over six geological formations, namely Nkporo Shale (NS), Ajali Sandstone (AS), False-Bedded Sandstone (FSS), Lignite-Claystone-Shale (LCS), Clayey Sand-Shale (CSS), and Alluvium (AL) were investigated. Results: Soil texture varied significantly among the geological formations, ranging from sandy clay loam and loam in soils developed over sandstone and alluvial formations to clay loam in soils underlain by shale formations. Soils of the Nkporo Shale formation were strongly acidic (pH 4.7) and recorded the highest exchangeable Al³⁺ (2.54 cmol kg⁻¹) and exchangeable acidity (4.59 cmol kg⁻¹). In contrast, soils developed over alluvial deposits were near neutral (pH 6.3) with lower acidity (1.13 cmol kg⁻¹). Cation exchange capacity and available phosphorus differed significantly across formations, and positive correlations were observed between base cations and base saturation. Conclusion: Underlying geological formations exert a strong control on soil physicochemical properties, fertility status, and acidity in the study area. Site-specific soil management practices tailored to individual geological formations are therefore recommended to enhance sustainable agricultural productivity.