Click on “Download PDF” for the PDF version or on the title for the HTML version.

If you are not an ASABE member or if your employer has not arranged for access to the full-text, Click here for options.

Soil-water dramatically influences infiltration and runoff and consequently water quality. In-situ measurements of soil-water are critical for understanding hydrologic and water quality processes. Precise in-situ measurements of soil-water are sparse. However, many advances have recently been made in soil-water measurement techniques. In particular, instruments for estimating soil-water from measurements of soil electrical properties have become very popular. While the instruments have been shown to be good indicators of relative changes in soil-water, questions remain regarding their ability to yield quantitative estimates. Most of these techniques rely upon a limited set of calibration equations obtained through laboratory analysis of homogeneous soil materials (i.e. sand, silt, and clay). This paper describes a validation study of two capacitance based soil-water probes for a range of Coastal Plain soils. The probes measure the capacitive and conductive properties of the soil. These measurements are then related to soil-water through calibration equations. Laboratory and field tests indicate that the probes track changes in soilwater and yield adequate relative estimates of soil-water. In most cases, the factory calibration was within +/- 50% of the observed soil-water. Results indicate improved relationships could be developed through laboratory tests. These probes should prove to be a useful tool for estimating soil-water in many Coastal Plain soils. However, additional work is required to evaluate better equations for absolute prediction of soil-water.