Analysis of soil samples treated with 10% (v/w) Escravos light crude oil and amended with chicken droppings and NPK fertilizer revealed that the aerobic heterotrophic bacterial counts were depressed while the proliferation of crude oil degrading bacteria (CDB) in the soil was encouraged. The counts of CDB in oil free (control) soil ranged from 20 x 108 CFU/g to 33 x 108 CFU/g of soil, while that of oil polluted soil ranged from 48 x 108 CFU/g to 93 x 108 CFU/g soil after 10 wks. In fertilizer amended soil, the counts of CDB ranged from 40 x 108 CFU/g to 92 x 108 CFU/g of soil and from 53 x 108 CFU/g to 95 x 108 CFU/g in soil amended with chicken droppings. The crude oil degrading bacteria were identified as species of Bacillus, Pseudomonas, Acinetobacter and Micrococcus. The isolate Bacillus sp. SOB-10 exhibited a high ability in degrading the crude oil. The organism degraded 54.6% of crude oil in 14 days and therefore, may be useful in seeding oil-polluted soil. Crude oil addition to soil raised the pH from 6.75 to 7.65 and amendment of the oil-polluted soil with chicken droppings further raised the soil pH (7.17 – 7.76). Amendment of the oil polluted soil with fertilizer however, caused a remarkable decrease in the soil pH (5.91 – 6.26). Biodegradation studies revealed that 56.3% of crude oil was degraded in the unamended soil while 75% and 87.5% of crude oil was degraded in soil amended with chicken droppings and fertilizer respectively after 10 wks. This indicates that chicken droppings and NPK fertilizer enhanced the biodegradation process.
Key words: Amendment, biodegradation, crude oil, soil.