(PH258) Impacts of soil treatments on crude oil degradation and maize performance.
Ekweogwu, J.C.1, Amadi, E.N.2, Odu, C.T.I.2, 1 Federal University of Technology, Owerri, Imo State, Nigeria, Nigeria2 Rivers State University of Science & Technology, Port Harcourt, Rivers State, Nigeria, Nigeria
ABSTRACT- Crude oil pollution affects arable lands through induction of nutrient deficiency, reduction in microbial population and adsorption of the oil to soil. This hampers natural biodegradative processes which can be enhanced through bioremediation strategies. Seven treatments previously established in the laboratory as optimal for crude oil degradation were assessed for their effects on oil degradation and nitrogen mineralization on oil-polluted sandy loam soil over a sixteen-week incubation period. The treatments included phosphoric acid (H3PO4) and animal wastes alone (cow dung and/or poultry manure) and in different combinations with surfactants and/or alternate carbon substrates. Crude oil degradation was determined by the toluene extraction method, nitrogen mineralization by nesslerisation and phenoldisulphonic acid methods. Greater oil degradations were obtained from soils given treatments containing H3PO4 than animal wastes due to ready availability of phosphorus in H3PO4-P for microbial growth. Addition of surfactants reduced the extent of crude oil degradation. The highest degradation of 16.54% was obtained from sample treated with Glucose + H3PO4 at 1.0 % (w/w) + 1000
gP/g soil. Oil pollution adversely affected nitrification, but this was ameliorated to different degrees more in samples given treatments containing animal wastes than H3PO4-P. Greenhouse studies on the impacts of these treatments after sixteen weeks incubation on maize growth showed that crude oil toxicity to maize was worsened in samples given treatments containing H3PO4 and ameliorated in samples containing animal wastes. Addition of surfactants and/or alternate carbon substrates did not (P>0.05) enhance maize performance. For an efficient clean-up to reduce the level of contaminant in the polluted soil, treatment of the soil with Glucose + H3PO4 is recommended. However, for restoration of agricultural productivity, the oil polluted sandy loam soil should be treated with a mixture of cow dung and poultry manure at 4.0 % (w/w) for sixteen weeks prior to maize planting.
Key words: surfactants, agricultural productivity, crude oil degradation, animal wastes