Afangide, A.I., Agim, L.C., Okon, M.A., Chukwu E.D., Paul, I., Okoli, N.H., Egboka, N.T. and Onwuka, V.C.

ABSTRACT

The research was aimed at investigating the impact of palm oil mill effluent (POME) on the biological and chemical characteristics of soil that had been exposed to POME pollution for many years. The target sampling technique was employed. Mini profile pits were sited at 0, 10, 20 and 30 years of palm oil mill effluent discharge points. Soil samples were collected at varying depths of 0 – 10cm, 10 – 20cm, 20 – 30cm, and 30 – 40cm.  Soil samples collected were analyzed for biological and chemical characteristics, and data obtained were subjected to analysis of variance, with significant means separated using the least significant difference. The results showed that the textural class of the soils was loamy sand. The pH was slightly acidic; mean values varied from 5.3 – 6.6. Total nitrogen increased from 0.07% – 0.12% while available phosphorus varied from 7.04 mg kg^-1 in unpolluted soils to 12.34 mg kg^-1 in soils exposed to POME for 30years. Total heterotrophic bacteria count ranged from 1.9×10⁴cfu g^-1 to 9.5×10⁵ cfu g^-1, with the highest mean value at the 30 years of POME-polluted site, and least at the unpolluted site. Actinomycete count increased from 2.0×10³ cfu g ^-1 in unpolluted soils to 9.6×10⁴ cfu g ^-1 in soils exposed to POME for 30 years. Bacteria had a positive relationship with total nitrogen (r=0.77**) and pH (r=0.75**). Bacterial genera identified at the sites were Bacillus cereus, Micrococcus spp, staphylococcus aureus, and Corynebacterium spp, while fungal genera were Rhodontorula spp, Mucor spp, and Aspergillus spp. The result confirmed that palm oil mill effluent improved microbial diversity and chemical properties of the soil relative to unpolluted site which are keys to measuring soil quality.