GEOELECTRICAL INVESTIGATION AND NEAR-SURFACE SOIL CHARACTERIZATION IN A ROADSIDE CULTIVATED PLANTAIN FARMLANDS ALONG ORU-IJEBU SOUTH-WEST NIGERIA

Abstract

The significance of quantifiable, regular and non-poisonous water for any agricultural practices crop processing, ornamental farming and animal husbandry cannot be over-emphasized. Considering the heterogeneity of the subsurface geological condition of any given environment, it is pertinent that adequate understanding of the subsurface hydrogeological conditions of the study area is necessary for successful and satisfactory exploration for groundwater, determination of protective capacity of the area. The study was conducted on 10 plantain farm-lands randomly distributed at unequal distance around Oru-Ijebu road. characteristics of the groundwater as well as the vulnerability through the protective status of the aquifer in Oru-Ijebu farmland was undertaken using Vertical Electrical Sounding Techniques accompanied by the laboratory analyses (bulk density, porosity, hydraulic conductivity and textural analyses) of the collected soil samples for determination of Physical parameters of interest from the farmland. Forty (40) vertical electrical soundings (VESORUPF1 to VESORUPF40) were conducted in the study area. The consequent iteration curves, true resistivity of the underlying layers, the thickness as well as true depth of overburden formations overlying the aquifer were obtained using resist software. The dominant resistivity sounding curve types obtained from the survey area were KH-types (????1 < ????2 > ????3 < ????4) followed by K-types (????1 < ????2 > ????3) and H-types (????1 > ????2 < ????3). The percentage frequency of the curve types is 52% for KH-types, 22% for K-types and 20% for H-types. Thickness of the top soil ranges from 0.4m to 5.2m and aquifer thickness of 1.70m to 20.9m. The risk of the groundwater for subsurface pollution and was assessed alongside the protective capacities of the geologic layers using the output of the electrical survey data thereby highlighting suitable areas of differential protective capacity rating while the specific categorization of the analyzed soil textural class according to international standard textural triangle classification of all profiles revealed sandy clay/sandy loam soil and there was a significant increase in soil moisture at 0.6m-0.8m and 0.8m-1.0m depth.