DETERMINATION OF THE TOLERANCE LEVEL OF Dioscorea bulbifera L. TO SOIL CONTAMINATED WITH SPENT ENGINE OIL AND INDUSTRIAL EFFLUENT

Abstract

Human activities and rapid industrial development have contributed immensely to environmental pollution and other public health hazards. Contamination of the environment constitutes a menace to plants and other soil organisms. This study was carried out at Federal University of Technology, Akure, Ondo State, Nigeria to investigate the effect of soil contaminated with spent engine oil (SEO) and industrial effluent (IE) soil on the growth and yield of Dioscorea bulbifera L. Four levels of concentrations: 0ml/15kg, 75ml/15kg, 225ml/15kg, 375ml/15kg of SEO and effluents from a Cocoa Industry Akure were evaluated levels assessed. Growth and performance of D. bulbifera were determined by taking the following parameters; sprouting, day of bulbil appearance (days), number of bulbils and weight (g), plant height (cm), leaf area (cm), leaf length (cm), shoot length (cm), chlorophyll content (mg/g) and the number of leaves produced by D. bulbifera in each treatment. The height, leaf length, shoot length and girth of the plant was measured using meter rule (cm), number of leaves and bulbils were determined by visual counting, chlorophyll content (mg/g) was measured using a spectrophotometer and weight (g) of tubers harvested were determined using Ohaus Analytical balance. The results showed that spent engine oil in soil has highly significant (P ≤ 0.05) effects on some of the soil physico-chemical properties. IE had the highest nitrogen content (0.89%) while 75ml/15kg had the lowest nitrogen content of 0.72%. pH was highest in control (4.29) and the lowest was at 375ml/15kg (4.89). The germination time increased with increase in treatment concentration, with control having the shortest time of 28 days and 375ml/15kg concentration having longest time of 53 days. The growth of D. bulbifera was delayed as the levels of treatment were increased. The control was signfinicantly different (P ≤ 0.05) from other levels of treatment, having highest value in height (576.67cm) while IE had the lowest (179.08cm). Control had the highest number of leaves (66.3) while IE had the lowest number (18.67). Likewise in leaf length, control had the highest length of 15.17cm while IE had lowest (9.07cm). In leaf area, control had the largest (141.69(x102) cm2) while the IE had the lowest (14.74(x102) cm2). The least chlorophyll content was observed in IE (274.06mg/g) and highest chlorophyll content in the control (349.60mg/g). In potassium (K) content of the soil after 16 weeks, there was significant difference among the treatment levels, while control (18.6) had the least amount and 375ml/15kg (30.02mg/kg) has the highest. The copper level of the control bulbils (0.01mg/kg) was significantly different (p < 0.05) from others, as the IE had the highest amount of copper (0.56 mg/kg), control (0.01mg/kg) had the lowest. Considering the detrimental effects of spent engine oil and industrial effluent pollution on plants in factory area, oil rich regions and mechanic villages, it has become necessary to screen for plants with strong tolerance to soil oil contamination and also oil pollution of agricultural soil should also be avoided.