Effects of Spent Engine Oil Polluted Soil and Organic Amendment on Soil Chemical Properties, Micro-Flora on Growth and Herbage of <i>Telfairia Occidentalis</i> (hook f).

Abstract

A trial was conducted at the Screen House of the Department of Crop Science, University of Benin, Benin City, Nigeria to evaluate the efficacy of using organic fertilizer as bioremediant for spent engine oil polluted soils. Three concentrations of spent engine oil (0, 5 and 10 % w/w, spent engine oil in soil) and three application rates of organic fertilize (0, 5 and 10 t ha^-1) were utilized in a 3 x 3 factorial arrangement and laid out as a completely randomized design with three replication. Soil pH, available P and exchangeable cations were significantly reduced by spent engine oil except organic C compared to control. Heavy metals (Va and Pb) concentration increased with increasing concentration of spent engine oil. Amendment of spent engine oil polluted soil with organic fertilizer significantly remediated the degraded soil and decreases the heavy metal concentration. In addition, 10 t ha^-1 organic fertilizer showed superiority over 5tha^-1 organic fertilizer in amending spent engine oil degraded soil for pH, total N, available P, exchangeable Ca²⁺ and reduced heavy metal concentration. Soil pollution adversely affected number of leaves, dry vine weight, dry leaf weight and herbage yield. Growth and herbage yield were much higher in organic fertilizer amended spent engine oil polluted soil. the highest herbage yield (9.23 t ha^-1) was obtained from unpolluted soil treated with 10 t ha^-1 organic fertilizer which was statistically comparable with soil polluted with 5 % spent engine oil and amended with 10 t ha^-1 organic fertilizer (7.10 t ha^-1). Soils polluted with 5 % spent engine oil had higher bacteria population compared to control, while organic fertilizer had depressing effect on soil without spent oil pollution. However, unpolluted soiltreated with 10 t ha^-1 organic fertilizer had the fungi (0.77 x 10⁶cfu g^-1) population which was statistically compared to 5 t ha^-1 organically treated soil without spent engine oil pollution (0.76 x 10⁶cfu g^-1). Soil polluted with spent engine oil has been bioremediated with organic fertilizer and hence put into productive use.

Keyword: Growth, herbage yield, micro-flora, organic fertilizer, spent engine oil, Telfairia occidentalis.