Effect of Soil Texture, Water Content and Temperature on Apparent Soil Electrical Conductivity

Abstract

Advances in apparent soil electrical conductivity (ECa) sensor technology have provided the opportunity to map soil texture (i.e., clay content) for purposes of site‐specific management. From theory, the relationship between ECa and soil stable property of clay content is governed by soil transient properties of water content, ion concentration, and temperature at the time of the ECa mapping. The objective in this study was to quantify the sensitivity of near surface ECa measurements to diurnal and daily variations in soil water content and temperature in two soils. A 14 × 10 × 6 ft deep excavated area was filled with dry sand, instrumented with soil water and temperature probes, and continuous measurements of ECa and soil water and temperature were taken for a few weeks. Measurements were taken for dry and wet soil conditions and under sandy and clayey top soils. Soil ECa showed a positive relationship with soil water content and temperature, with much higher sensitivity to soil water than temperature. Results show a distinct diurnal trend in ECa very similar to diurnal variations in soil temperature. Sensitivity was greater in the clayey than in the sandier soil. Results from the experiments and from a simplified modeling are compared and implications discussed.