Abstract: A laboratory experiment was carried out to investigate the kinetics of available nitrogen and the effects of water potential and nitrogen supplement on the biodegradation of crude oil. Crude oil with the rate of 100 g/kg soil was ineffective to soil water potential. Water potential with the range of -100～-20 kPa had no effect on the biodegradation of crude oil. The degradation rate of the total petroleum hydrocarbon (TPH) decreased by 10%～30% as compared to the control with water potential of -1000 kpa. The most favourable C/N ratio to the biodegradation of crude oil was 90 in Weswood soil while with the ratio of 60 toxic effect occured to the biodegradation of crude oil. 

Key words: soil, crude oil, biodegradation, water potential, nitrogen