In this experiment, all values were expressed as the mean of two replicates. Fig. 1 to 3 represents the
percentage of TPH removal in each treatment. For contaminated soil without any additive (CS), Fig. 1 shows
that after the first two weeks, the (TPH) removal was 27 % of the initial concentration. It is hypothesized that
the reduction of TPH may be due to the improvement of some conditions such as humidity and ventilation. At
the end of experiment, the total TPH removal was 52.4%. This suggests that there has been improvement in
soil properties and conditions comparing with the conditions in the beginning of the experiment.
While previous studies by other researchers [4, 11] were are not in support of the hypothesis that nitrogen
and phosphorous based additives improve the biodegradation process, the result of this study found that TPH
removal in the first two weeks for the contaminated soil received poultry manure (CS+ORG) remarkably
increased to 58.8% comparing to that obtained with CS sample during the same period (Fig.1). After two
weeks, a gradual increase in the removal of TPH (2.3 %) was observed with CS-Org until the end of treatment
period where the removal rate reached its maximum of 72%. Comparing CS-Org sample to the CS, the rate
difference was 19.8% which is confirming the fact that the natural organic fertilizers would improve the rates
of biodegradation.