Effects of Soil Resistivity Variation with Depth on Crop Yield in a Typical Sedimentary Terrain, Igieduma-Edo State, Nigeria: A Geophysical Method Application in Agricultural Practice

Abstract

Accurate knowledge of soil fertility is required to promote global food security for life sustenance. Literatures have shown that electrical resistivity method is effective for agricultural site selection without passing through the rigor of soil test. However, the factor responsible for inconsistence in resistivity signature with soil fertility from one place to another, effect of soil texture and depth variation on crop yield are the questions this work geared at providing answers. Ten Vertical Electrical Sounding (VES) were conducted across the study area using Schlumberger array. Res1Dinvers was used for the inversion model, using Least Square method. Twenty soil samples were obtained in the VES points, two samples per point. One sample each at first and second layer. Result of the apparent resistivity showed that areas with high-excellent crop yield have resistivity signature above 500 Ωm while areas with low yield are characterized by values less than 500 Ωm. In both areas of low and high-excellent crop yield, the result of geochemical analysis indicated that Nitrogen, phosphate, and Potassium varied as 59-61%, 43-54mg/kg and 49-51mg/kg, respectively except for organic matter content that was above 3.8% in the first layer have high-excellent yield while low yield soil showed less than 3.8% in their first layer and even if the second layer’s organic matter is above 3.8%. This study has shown that organic matter has significant effect on soil resistivity signature than others soil nutrients (Phosphate, Potassium and Nitrogen). The study shows that soil’s first layer (0-0.3m) is the most suitable depth conducive for soil minerals occurrence for optimum agricultural output.