Effect of Bitumen Deposits on the Physical Properties and Hydraulic Conductivity of Sandy Loam Soil in Ondo State, Southwest Nigeria.

Abstract

The effects of bitumen deposits was investigated on soil samples from three locations in Irele area of Ondo state (Loda, Lofo and Legbogbo sites) where Loda and Lofo are bituminous soils while Legbogbo is bitumen free. Soil samples were collected at 0 – 15 cm depth from five points for the experiment. Loda had the lowest moisture content (MC) (12.65 %) at 0-10cm depth and legbogbo had the highest at 40 -50 cm depth (18.39 %). The moisture content values for Legbogbo increases down the soil profile at a consistent soil moisture depth from the least to the highest. It was observed that Loda had the highest MC due to hard deposits of bitumen. The soil bulk density (BD) was significantly affected by soil depth (p ≤ 0.001). In Legbogbo, there was increase in the BD down the soil depths. Loda had the lowest BD (1.54 gcm-3 ) at 40-50 cm depth while Lofo had the highest BD (1.68 gcm-3 ) at 30-40 cm. Legbogbo had the highest mean of 9.02 cm/s while the mean hydraulic conductivity for Loda was 6.41 cm/s and Lofo had 5.61 cm/s showing that Legbogbo is significantly different. Tukey pairwise comparisons at 95% confidence level shows that mean of hydraulic conductivity for Loda - Legbogbo and Lofo – Legbogbo are statistically and significantly different while the mean of hydraulic conductivity values of Lofo – Loda is not significantly different, which may be due to bitumen deposits and the compaction which affects infiltration or permeability