except at concentration 30% after three months (Figure 1(a)). It was also observed that the organic matter of
soil contaminated with from zero to 20% concentration used engine oil and inoculated with P. ostreatus was
higher at six months. Also, there was a progressive increase in the organic matter when P. pulmonarius was inoculated
after six months (Figure 1(b)).
As the percentage of crude oil increased, there was increase in percentage carbon (% C) in soils inoculated
with P. ostreatus after 3 and 6 months. Percentage carbon also increased in soil contaminated with engine oil
and inoculated with P. pulmonarius after 6 months. However, there was slight decrease in % C of all the soils
with P. pulmonarius when compared with P. ostreatus after 3 and 6 months of contamination with crude and
engine oils (Figure 2(a) and Figure 2(b)).
A general decrease was observed in percentage nitrogen (% N) as the concentration of crude oil applied increased
in soils treated with P. ostreatus and P. pulmonarius after 3 months. The % N of soils treated with crude
oil and inoculated with P. ostreatus was higher than that inoculated with P. pulmonarius after 3 and 6 months
(Figure 3(a)). There was a progressive decrease in nitrogen content of soil with increase in concentration of
used engine oil and inoculated with P. ostreatus whereas that of P. pulmonarius increased after three months
from concentration 5 to 20. Also, the nitrogen content of soil inoculated with P. pulmonarius was higher than
that of P. ostreatus after six months (Figure 3(b)).
Generally, there was increase in phosphorus content of soil samples contaminated with crude oil and inoculated
with P. ostreatus and P. pulmonarius after the third and sixth months from concentrations 5% to 20% although
the phosphorus content of P. ostreatus inoculated soil was higher (Figure 4(a)). Similar trend was ob-
(a) (b)
Figure 1. (a) Percentage organic matter content of soil contaminated with crude oil and inoculated with Pleurotus species; (b)
Percentage organic matter content of soil contaminated with engine oil and inoculated with Pleurotus species. A: Soil inoculated
with P. ostreatus after 3 months. B: Soil inoculated with P. pulmonarius after 3 months. C: Soil inoculated with P.
ostreatus after 6 months. D: Soil inoculated with P. pulmonarius after 6 months.
(a) (b)
Figure 2. (a) Percentage carbon content of soils contaminated with crude oil and inoculated with Pleurotus species; (b) Percentage
carbon content of soils contaminated with used engine oil and inoculated with Pleurotus species. A: Soil inoculated
with P. ostreatus after 3 months. B: Soil inoculated with P. pulmonarius after 3 months. C: Soil inoculated with P. ostreatus
after 6 months. D: Soil inoculated with P. pulmonarius after 6 months.