Investigation of Soil Moisture Content In Soil under Different Preparation Modes Using Electrical Resistivity and Guided Wave Sounding Methods

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Continuous vertical electrical sounding (CVES) and the guided wave sounding (GWS) methods were used to investigate the soil moisture content of a maize farm at the KNUST Agricultural Research Station (ARS), Anwomaso, Kumasi – Ghana. The soils of the maize farm were categorized with four di erent land preparation modes; ploughed-harrowed, ploughed, hoed and no-till plot. Time-lapse measurement of the CVES was carried out using the multi-electrode Wenner array to produce 2D resistivity models as a result of soil moisture variation with the help of the ABEM Terrameter SAS 4000 resistivity meter. The GWS method (an invasive application of the ground penetrating radar (GPR)) retrieved the soil moisture content by analyzing reflections from the lower end of a metal rod with the help of an access tube preinstalled in the soil and a GPR system with 800 MHz shielded antenna. The results showed a heterogeneous distribution of soil moisture content both spatially and temporally. Most of the water available for plants’ uptake was within a depth of 0.20 – 0.40 m which coincided with the root zones of the maize crops. In addition, the no-till plot was found to conserve more moisture during dry weather conditions than the rest of the plots. The research shows that CVES and GWS techniques are e cient in monitoring shallow soil water content in the field and the results obtained could be used to optimize irrigation scheduling and to assess the potential for variable-rate irrigation.
A Thesis Submitted to the Department of Physics, Kwame Nkrumah University of Science and Technology in partial fulfillment of the requirements for the degree of Master of Philosophy (Geophysics)