Effects of crude oil contaminated-soil on the germination and growth of cowpea Vigna unguiculata (L.) Walp

Abstract

A greenhouse experiment was conducted to investigate the germination and growth response of cowpea (Vigna unguiculata
(L.) Walp) to soils contaminated at different concentrations of crude oil. This was done with a view to access the impact
of crude oil pollution on growth and nutrient content after harvest. The contaminated crude oil polluted soils were
prepared at different concentrations of 0.0, 10.0, 20.0, 30.0, 40.0 and 50.0 (w/v) on 5 kg each of air-dried soil collected from
the Obafemi Awolowo University Biological Garden rich in organic matter. Each treatment was replicated three times and
arranged in complete randomized design. The following parameters, leaf length, breadth and leaf number, N and protein
were determined. Results showed that leaf length, breadth and leaf number were significantly higher (p<0.05) recorded in
the control pots. The least % N and protein were recorded in the pots with highest crude oil concentration (50.0 ml). The
results also showed that increasing crude oil concentration, posed higher risk of edibility of the test-plant and no
detectable amount of petroleum hydrocarbon was found in the soils at the end of the experiment. The study concluded
that although cowpea germinated and grew well in crude oil-contaminated soils, its nutrient content was impaired and
edibility not guaranteed.