Agronomic Evaluation of Remediated Oil-impacted Soils: A Comparative Study of Nutrient Dynamics and Soil Quality in K-Dere, Ogoniland
Lebari Sibe *
Biochemistry/Chemistry Technology, School of Science Laboratory Technology, University of Port Harcourt, Choba, Rivers State, P.M.B. 5323, Nigeria.
Amarachi Wonodi
Department of Chemistry, Faculty of Natural and Applied Sciences, Ignatius Ajuru University of Education, Port Harcourt, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
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 <0.053 mg/kg), phosphorus (0.15 mg/kg - 0.90 mg/kg) and total organic matter (TOM: 0.579 % -1.064 %,) were observed in composite soil samples in non-remediated and remediated sites Remediation practice declined essential nutrients and potassium (23%), magnesium (59%), cation exchange capacity (65%), Zinc (44%) and copper (55%).
Conclusion: Soil remediation improved the quality and restored several soil parameters to acceptable agronomic levels, but significantly declined the levels of essential plant nutrients. Targeted nutrient supplementation, continued organic amendment, and regular soil monitoring are therefore recommended to sustain crop productivity on remediated Ogoni farmlands.
Keywords: Soil, remediation, agriculture, mineral elements, soil fertility, physicochemical properties