TITLE:
Impact of Crude Oil on Soil Nitrogen Dynamics and Uptake by Legumes Grown in Wetland Ultisol of the Niger Delta, Nigeria
AUTHORS:
Richard C. John, Emem S. Ntino, Alfred Y. Itah
KEYWORDS:
Impact, Crude Oil, Soil Nitrogen Dynamics, Legumes, Wetland Ultisol, Niger Delta
JOURNAL NAME:
Journal of Environmental Protection,
Vol.7 No.4,
March
17,
2016
ABSTRACT: The effects of crude oil on soil nitrogen
dynamics and cycling in plant-soil ecosystems and its effect on the growth of
legumes (Calopogonium mucunoides, Centrosema pubescens and Pueraria
phaseolodes) grown in wetland ultisols were investigated. The test
plants species were grown on wetland soil simulated with 0.35, 10.8, 20.5, and
50 g.kg-1levels of crude oil contamination. The results
showed time and species dependent variation in mineral N content of the treated
soils. The variation is indicative of significant interaction between the
hydrocarbon content and plant species. Variations in microbial N and microbial
C were similar and correlation between the microbial N and the total C (Organic
matter (C) + hydrocarbon content (C)) in soil was highly significant (r = 0.96,
n = 12, P ≤ 0.01). The presence of hydrocarbon contaminant widens the C:N ratio
in soil and leads to more available N being immobilized by soil microorganisms,
which reduces available N for plant uptake. This result implies that crude oil
contamination significantly reduces N uptake by plants but increases N
accumulation in soil microbial biomass. The findings show that N dynamics,
transformation and cycling in soil are influenced by hydrocarbons and that the
interactions between hydrocarbon content and plant species in contaminated soil
are remarkable. The use of plant Centrosema pubescens with
poultry manure or NPK fertilizer for bioremediation is more effective than that
of Calopogonium mucunoides and Pueraria
phaseoloides. However, the selective attributes of the
various treatment approaches adopted here may be exploited for enhanced
remediation of contaminated wetlands in the Niger Delta region of Nigeria.