Combined Geophysical and Soil Test Analysis Methods for Soil Precision Mapping in The Delta State University CES Farm Abraka Nigeria

Abstract

Geophysical methods and soil test analysis have been used to study soil properties in the farm of the Centre for Entrepreneurial Studies (CES), Delta State University Abraka Nigeria. Vertical electrical sounding (VES), borehole geophysics, electrical resistivity tomography (ERT) and geochemical methods were used for the study. Seven VES stations were occupied along five traverses used for ERT measurements. Samples of soil close to the VES stations were taken for soil testing and study of grain size to corroborate the results of VES and ERT. The low resistivity of the topsoil obtained from the VES agrees with the ERT and borehole log results and this ranges from fine grained silt topsoil to sandy clay. This is a product of partial decomposition of plants and animals forming organic matter, and ranges from 168–790 Ωm with mean value of 494 Ωm and average depth of 2.3 m. This depth covers the upper root region of some important crop and depict a high amount of moisture and mineral nutrients, and a fair degree of stoniness to aid adequate rooting of the crops. Also, the observed topsoil is high in porosity and water retention which are major suitable factors for the yield of tuber and stem plants. The soil test results gave pH: 6.13–7.16, organic matter: 6.48–8.66%, Nitrogen: 65.72–78.21%, Phosphorus: 53.32–67.43%, Copper: 14.16–22.61 mg/kg, Nickel: 1.16–3.11 mg/kg, Lead: 4.00-8.84 mg/kg, Arsenic: 0.08–0.1 mg/kg Iron: 96.33-151.63 mg/kg. These recorded concentrations are below the WHO standard for crop production.