RESUMEN
The bio-stimulation of hydrocarbon degrading microbial population in soil using agricultural wastes was carried out. Top soil (0-25 cm depth) from three points were bulked to form composite soil samples, 6 kg each of the composite soil sample was weighed and transferred into 150 plastic buckets with drainage holes at the base. The soil in each plastic bucket was spiked with 300 ml crude oil and amended with different concentrations of agro-wastes and allowed for duration of 30, 60 and 90 days. The soil samples were then collected and analysed for both total heterotrophic bacterial counts and crude-oil utilizing bacterial counts. Data collected were subjected to a three-way analysis of variance and significant means were separated using Least Significant Difference Test at 5% probability level. The result showed that the application of the amendments increased the bacterial counts in the soil at different treatment levels. However, a higher proliferation rate was observed with bacteria counts exposed to higher waste concentrations compared to their counterparts exposed to lower waste concentrations. The phylogenetic relationship of the hydrocarbon degrading bacterial species shows that the identified bacteria were in two clusters: cluster 1 consist of Bacillus cereus, Bacillus thuringiensis, Bacillus altitudinis, Pseudomonas aeruginosa, Proteus mirabilis and Proteus penneri, while cluster 2 consist of Serratia marcescens, Providencia rettgeri and Enterobacter asburiae. The bacterial species obtained shows a greater relationship, this imply that the similarity of the bacterial species could be the reason for their high proficiency in degrading the hydrocarbons in the soil.
RESUMEN
In the present study the tolerance potentials of T. cacao in hydrocarbon polluted soil was evaluated. Top soil (0-25 cm depth) was collected from three points, bulked to form composite soil sample. Eight kilograms of the soil sample each were weighed into twenty five (25) perforated bags. The bags were polluted with 0 ml/kg, 50 ml/kg, 100 ml/kg, 150 ml/kg and 200 ml/kg of crude oil respectively with five replicates for each concentration and allowed for 2 weeks before planting. Three seeds of cocoa were sown in each of the polythene bags. Water was applied every three days to keep the soil moist. The results showed that cocoa plants at 8 weeks after planting (WAP) had significantly higher height (P<0.05) than those of 4 weeks after planting (WAP). The plant height, petiole length, number of vine had no significant difference (P>0.05) at the different concentrations of crude oil. While the leaf length, leaf area, number of leaves, leaf width and vine length shows significant difference (P<0.05) and in treatment dependent manner. The results also showed that the concentrations of Cu, Ni, Cr and Zn in the polluted soils were treatment dose dependent but did not significantly affect the plant tolerance at P<0.05. The pH, phosphorus, nitrogen content, and other physicochemical properties of the soil were not significantly affected by the crude oil treatment. The T. cacao has been found to be tolerant to hydrocarbon polluted soil environment, its usage in oil spill impacted area should be encourage.