Mitigation of the Effect of Crude Oil Polluted Soil on the Growth and Development of Cassava-Manihot esculenta Crantz with Organic and Inorganic Amendments

NPK and compost of Centrosema pubescens were studied at the University of Port Harcourt Botanic garden for their effect on the growth components of Manihot esculenta, Crantz (NR 8082) in a crude oil polluted soil. The soil samples were polluted at four different levels (0%, 2%, 4% and 6%) with crude oil and amended with organic supplement (decomposed Centrosema pubescens) and NPK fertilizer at the rate of 0.25 Kg per 5 Kg of soil to the various levels of crude oil contaminated soil, alongside a control. A total of 48 plastic buckets were used, each treatment was replicated three times.

Mean values of Physico- chemical properties of experimental soils were expressed. Quantitative observations showed that amelioration treatments recorded significant (P=0.05) increase in plant height, petiole length, leaf number, leaf area, fresh weight, dry weight and moisture content, than those of the control. Results of edaphic physico-chemical parameters showed that crude oil pollution at P=0.05 significantly increased percentage total organic carbon, total organic matter and total hydrocarbon content (THC) while pH, percentage total nitrogen, phosphorus and cation nutrients (Ca, K and Mg) were significantly decreased at two weeks after pollution. The results also showed that the amendment treatments at P=0.05 significantly decreased crude oil toxicity at different degrees by improving the nutrients content and decreasing the total hydrocarbon content of the soil.

Therefore, Centrosema pubescens and NPK fertilizer in single and combined treatments is effective in remediation of crude oil polluted soil for cassava cultivation.