Agronomic Evaluation of Remediated Oil-impacted Soils: A Comparative Study of Nutrient Dynamics and Soil Quality in K-Dere, Ogoniland

Background and Objectives: This study investigated the effectiveness of remediation practices on agricultural soils and crop cultivation in Ogoni, Rivers State, Nigeria, with emphasis on soil fertility and physicochemical suitability for agriculture. The aim was to comparatively evaluate essential mineral elements and key soil properties in remediated and non-remediated farmlands to determine whether remediation restored agronomic functionality beyond contaminant reduction. Methods: Topsoil samples (0–15 cm) were collected from remediated and non-remediated sites in K-Dere community and analysed using standard laboratory procedures. Soil pH and electrical conductivity were measured using calibrated digital pH and conductivity meters, while moisture content was determined by oven drying at 105 °C. Particle size distribution was assessed using the hydrometer method, and porosity was derived from bulk density relationships. Total organic matter was analysed by the Walkley–Black wet oxidation method, and cation exchange capacity was determined through ammonium acetate extraction followed by titration. For mineral analysis, nitrogen was measured using the Kjeldahl digestion apparatus, available phosphorus was determined calorimetrically with a UV–visible spectrophotometer, potassium and calcium were analysed using a flame photometer, and magnesium, zinc, copper, and iron were quantified using atomic absorption spectrophotometry. Sulphate was measured turbidimetrically. Findings: Stable soil pH (6.23–6.21), declined electrical conductivity (98 - 60 µS/cm), and increased porosity (45 % - 49 %) within recommended limits were recorded. Increase in soil nitrogen (0.029 mg/kg