This study investigated the heavy metal content and microbial composition of
rhizosphere of
Panicum maximum
obtained from some auto mechanic workshops in Benin City,
Nigeria. The grass was uprooted and soil sample was taken from its rhizosphere. The sample
were labeled appropriately and immediately transported into a polythene bag covered with
aluminium foil papers. It was then taken to the laboratory for heavy metals and microbial assay.
The results showed that average plant density of
Panicum maximum per 100m
2 of sampled
subplots in the mechanic workshops was 8.50 in Ikpoba-Okha and 9.00 in Oredo, compared to
27.50 in the control. Fe content of rhizospheric soil in Ikpoba-Okha was 1527.6 mg/kg and
1653.1 mg/kg in Egor, compared to 1002.2 mg/kg in the control. Mean heavy metal content of
rhizospheric soils was 11.71 mg/kg of Mn, 0.031 mg/kg of Pb, and 9.98 mg/kg of Cr. Total
hydrocarbon content ranged from 1445.0 – 2314.2 mg/kg in the oil-polluted soils, compared to
851.5 mg/kg in the control soil. Total bacterial count of the rhizospheric soils collected from
Ikpoba-Okha sampling site was 5.40 x 10
6 cfu/g; 5.30 x 10
6 cfu/g in Ovia NE, and 4.90 x 10
6
cfu/g in Egor, compared to 0.39 x 10
6 cfu/g in the control. Comparatively, bacterial counts
outnumbered fungal counts. Percentage hydrocarbon degrading fungi was 133.3% in samples
collected from Oredo, compared to 31.82 in the control. The most prevalent fungal species was
Aspergillus niger
, whereas
Micrococcus varians
was the most prevalent bacterial species.
