Phytoremediation potential of Gliricidia Sepium (Jacq.) walp in spent engine oil polluted soil: effect on growth and soil physicochemical properties

Greenhouse experiment was conducted for 17 weeks to investigate the effects of spent engine oil (SEO) in the following concentrations: 0%, 2.5%, 5% and 10% (v/w), on the growth of Gliricidia sepium (GS), and its potential to phytoremediate and improve the soil physicochemical properties. Growth parameters and physicochemical properties including plant height and girth, bulk density, porosity, pH, nitrogen (N), phosphorus (P), potassium (K) and Total Organic Carbon (TOC) were determined during the study. There were no significant differences in plant heights and girth between the control (0%) and polluted soil (2.5%) throughout the study. In weeks 3–17, plant height in polluted soils, 5% and 10% were significantly lower than in the control and polluted soil (2.5%). Plant girths were not significantly different in polluted soils throughout the study. Polluted soil, 10% had the lowest plant height and girth (36.33 and 2.47 cm respectively) while the control (0%) had the highest (45.53 and 3.30 cm respectively) at the end of the study. Bulk density was reduced in polluted soils whereas porosity increased in week 17. N, P and K were reduced in the polluted soil while higher TOC was recorded in polluted soils, 2.5, 5 and 10% (2.11, 2.33 and 2.98 respectively) in week 17. This study showed that low SEO pollution in soil has no significant effect on GS height and girth but higher concentrations of SEO may negatively impact GS height and girth growth. GS can improve the physicochemical properties of SEO polluted soils.