This study investigated the effect of Glomus hoi and Pseudomonas aeruginosa on the degradation of petrochemical effluent polluted soil using Amaranthus cruentus as the test plant. This was with a view to determining the degrading potential of the microorganisms on soil polluted with effluent and its effect on the growth of the test plant.Eight different treatment layouts were used with three replicates for each level of pollution in the treatment layout. Ninety six (96) pots, each containing three kilograms of soil from both sterilized and unsterilized soil were used for the study. Fifty (50) grams of soil inoculum from propagated Arbuscular mycorrhiza was inoculated to a set of twenty four (24) experimental pots containing both sterilized and unsterilized soil before A. cruentus seedlings were transplanted to them. Another set of twenty four (24) pots containing both sterilized and unsterilized soil were injected with thirty (30) mL of P. aeruginosa inoculum before transplanting A. cruentus seedlings to them. The third set of twenty four (24) pots received dual inoculation of both fifty (50) grams of soil inoculum containing G. hoi and thirty (30) mL of P. aeruginosa inoculum before A. cruentuswere transplanted to them. The residual twenty four (24) pots served as the control. Thereafter, pot preparation was arranged in the screenhouse in a randomized block design. The A. cruentus seedlings were raised in nursery for a period of one week before they were transplanted to the pots; seedlings were left for 3 days to overcome transplanting shock before contaminating the soil with Petrochemical Effluent at various concentrations of 0%, 2%, 4% and 6% v/w. The seedlings were allowed to grow for eight weeks before the termination of the experiment. Plant Heightwas recorded weekly. The results obtained were analyzed using Duncan Multiple Range Test (DMRT) and other descriptive statistics.The pre planting analysis of soil showed that heavy metals analyses (chromium and cadmium) of sterilized soil had a lower concentration compared to the unsterilized soil. Total Petroleum Hydrocarbon (TPH) analyses revealed that dual inoculation of G. hoi and P. aeruginosa was effective in reducing TPH compared to when the microorganism was administered singly. Treatment with P. aeruginosa showed high TPH reduction potential compared to G. hoi. However, treatment without any inoculation of microorganism had the lowest rate of TPH reduction of 33% at 6% effluent concentration, the TPH in the soilreduced without inoculation with microorganisms but in a slower rate compared to those with single or dual inoculations. This study opined that the combineduse of G. hoi and P. aeruginosa was more effective in degrading petrochemical effluent polluted soil than when either is used singly.
