Abstract

This study assessed the physicochemical parameters of rhizospheric soils of two ruderals (Axonopus compressus and Eleusine Indica) and identified Plant Growth Promoting Rhizobacteria (PGPR) from them. Twelve rhizospheric soil samples were collected around the roots of the two selected ruderals from automobile workshops in four local government areas (L.G.A.) in Edo State. The physicochemical parameters and total hydrocarbon content (THC) were based on standard methods. Heavy metals were determined using atomic absorption spectrophotometry. Bacterial isolation was based on pour plate technique with subsequent in-vitro screening for PGPR activities such as phosphate solubilization, nitrogen fixation, indole acetic acid production (IAA) and ammonia production. Available phosphorus, calcium and magnesium were highest (P < 0.05) in samples of E. indica in Egor L.G.A. Zinc concentration was highest (33.84 ± 8.51ml/L) while cadmium was the least (0.07 ± 0.02 ml/l). THC (1188.7 ± 65.50) was highest in E. indica soil in Egor L.G.A. as well as organic carbon and organic matter contents but was least (775 ± 75.00 mg/L) in A. compresssus soil from Ovia North L.G.A. Bacterial count was highest in ruderal soil of A. compresssus (157 ± 5.00 × 103cfu/g) and least in that of E. indica (30.00 ± 1.00 × 103 cfu/g) in all automobile workshops from Ovia North East L.G.A. Three Gram positive bacteria and five Gram negative bacteria were obtained from ruderals soils. Enterobacter spp., Escherichia spp. and Salmonella spp. exhibited positive plant growth promoting activities. Studied soils contain rhizobacteria that can enhance plant growth and survival under severe environmental conditions.

Keywords: Plant Growth Promoting Rhizobacteria, hydrocarbons, automobile workshops, bacteria,