Effect of Soil Contamination with Crude Petroleum on Cowpea: An Insight into the Prospects of Crop Production in Nigerian Frontier Basins

Petroleum hydrocarbon contamination remains a major challenge confronting soil health, environmental sustainability, and food security in oil exploration areas. In this study, the effect of Bonny Light crude oil on cowpea (Vigna unguiculata L. Walp.) was investigated with a view to assessing its toxicity to plant growth and performance. Pristine soil samples were collected in different pots and contaminated with crude oil to achieve 0.0%, 2.5%, 5.0%, 7.5% and 10.0% v/w contamination levels. Viable seeds of cowpea were planted and monitored for the emergence and subsequent growth for a period of 12 weeks. Results showed that the crude oil extended the period of seed germination and delayed the emergence of sprouts by 2 days at a rate of 96.7%, 80.0%, 50.0%, 96.7%, and 73.3% emergence respectively. The plants’ shoots, roots, and leaves lengths were longer in control than in the contaminated soil. Phytotoxicity study showed that shoots, roots and leaves lengths of the plants were significantly reduced by ≥ 50% of the control. The relative plants' weights, chlorophyll, and the number of leaves were worst affected especially in plants grown in higher crude oil concentrations where fewer or absence of leaves was observed at the end of the experiments. No yield parameter was observed in all plants grown in contaminated soil as opposed to the control where flowers, fruits, and seeds were produced. The findings illustrated that the growth rate of V. unguiculata was severely affected due to hydrocarbon contamination in a concentration-dependent manner. It further demonstrated the imminent danger to food security especially in frontier basins with impending oil exploration activities. Therefore, there is a need to identify and integrate effective measures that minimize or prevent oil spillage in the course of oil exploration activities with a view to avoiding the repeat of persistent pollution problems disturbing host communities