Growth Responses of Chromolaena odorata, Axonopus compressus and Aspilia africana Grown on Spent Engine Oil Polluted Soil

Background and objective: The resultant effect of indiscriminate disposal of spent engine oil is a trending issue in most developing countries of the world causing adverse effects on plant growth and development. This study was conducted to ascertain the morphological responses of Chromolaena odorata, Axonopus compressus and Aspilia africana grown in used engine oil-polluted soil. Materials and Methods: An equal volume of pre-sieved soil (20 kg) was filled in polythene bags and arranged at 0.5 m spacing between polybags and 1 m between replications and perforated at the base to avoid water logging. Concentrations of spent engine oil spiked included 0, 4, 8, 12 and 16% (v/w) which was allowed to stabilize for 2 weeks to simulate the condition of the natural spill. Parameters recorded at 2 weeks intervals were: Plant height, number of leaves per plant, fresh weight and root number. Results: A dose-dependent decrease in plant height, number of leaves per plant, fresh weight and root number. The mean growth parameters of the control (0%) were significantly higher than that of plants exposed with 4, 8, 12 and 16% concentrations of spent engine oil at p<0.05%. Trends in marked reduction of growth parameters were as follows: A. compressus>C. odorata>A. Africana. Conclusion: Findings in this study underscore the need to further probe Chromolaena odorata, Axonopus compressus and Aspillia africana as possible plant species for remediation of used engine oil polluted soil in the tropics. These findings also validate the need for recycling and reuse of spent engine oil to forestall further pollution of the ecosystem.