Comparative Analysis of Compost Manure and Inorganic Fertilizer on the Bacterial Population Density of Cocoa Seedling Rhizosphere

Article history: Received 03 May 2019 Revised 11 May 2019 Accepted 15 May 2019 Available online 12 June 2019 Soil quality has been known to have a strong effect on cocoa tree growth and the interactions of plant and microbe in the rhizosphere influence plant health, productivity and soil fertility. In this study, the rhizospheres of cocoa seedlings were analyzed for bacterial density population after soil amendment. Cocoa seedlings were self-grown in nursery located at the Orchard of the Faculty of Agriculture, University of Benin and Amelonado variety Tc1-Tc8 pods were used. The seeds were prepared, pre-germinated and planted in bags containing 5 kg top soil. Organic fertilizers (compost poultry manure and cow dung) and inorganic fertilizer was applied to the soil surrounding the seedlings at one month after planting. The sowing soil and the rhizosphere of the cocoa seedlings at one month to four month were collected and analyzed. Serial dilution method was used for culturing and bacterial isolates were identified by Gram staining and various biochemical methods. The isolates were further characterized by DNA extraction, PCR and sequencing. All isolates belong to the phyla Proteobacteria, save one which belongs to the phylum Firmicutes; all of which are predominately found in the soil. The result revealed that the rhizosphere of seedlings amended with inorganic fertilizer recorded the least bacterial activity (2.35 x 10 5 – 3.05 x 10 5