Resolution of spatial variability of apparent electrical conductivity in agricultural soil assessment

Precision agriculture requires soil nutrient evaluation via chemical assessment, which is costly and requires painstaking laboratory analysis, whereas the geophysical technique has gained acceptance worldwide as an economical alternative. This research focused on the effectiveness of physical parameters in determining soil quality. The investigation was limited to 0.3-m soil depth at the kola farm of the Cocoa Research Institute of Nigeria, Ibadan. Seven hundred sites were occupied with earth resistivity and VG-meter-200 moisture meters measuring apparent electrical conductivity (ECa) and volumetric water content, respectively. Falling-head permeability was performed on ten cored soil sample. Forty-two samples were analyzed for textural variations using the Bouyoucos method. The soil ECa (12–545 μS/cm) was classified into 1–49 μS/cm, 50–99 μS/cm, >100 μS/cm as low ECa (LECa), moderate ECa (MECa), and high ECa (HECa), respectively. The deduction showed that soil ECa has high (82.83%) and moderate (59.35%) variabilities during the wet and dry periods, proving to be a soil quality assessor on which other investigations could be predicated. Soils’ permeability varied from 6.2 × 10−6 to 8.36 × 10−4 cm/s; infiltration rates were rapid (LECa), moderate (MECa), and low (HECa), accounting for the varying moisture retention capabilities. Soils of LECa have low permeability (3.40 × 10−4–8.36 × 10−4 cm/s) and are noted for rapid infiltration, which promotes nutrient leaching. The soil textures were sandy loam-98% (HECa/MECa/LECa) and loamy sand-2% (LECa). The HECa region has a high clay and silt content, which helps the soil retain nutrients. The study has shown the efficiency of the apparent electrical conductivity in appraising soil quality variability.