The difference in microbial population is also a reflection of many factors such as nutrient and oxygen levels, temperature and availability of minerals [33]. The differences in both bacterial and fungal populations could then be attributed to possible change in nutrient and oxygen supply to the soils.
The growth performance of maize and cowpea grown on crude oil polluted soil was poor compared to unpolluted ones. Etiolating leaves were evident in both plant treatments which is a strong indication of nutritional deficiency imposed by crude oil pollution. Poor aeration of the soil which results in root stress might also be a factor. This is in agreement with the findings of [34] which states that root stress reduced leaf growth via stomata conductance.