Submitted to: Methods of Soil Analysis
Publication Type: Book / Chapter
Publication Acceptance Date: 10/27/2000
Publication Date: N/A
Technical Abstract: The soil moisture characteristic curve is the relationship between water content and water potential. It must be known for a wide variety of hydrologic and agronomic modeling purposes, but it is difficult to measure accurately, particularly at the dry end of the curve, where extraction of water is time consuming and it is difficult to know when equilibrium has been reached. The thermodynamic similarity between drying a soil and freezing a soil offers an attractive alternative, if the assumptions underlying similarity are met. Since water potential in a frozen soil is a unique and predictable function of temperature, it is relatively straightforward to generate a known water potential. At the same time, the liquid water content in a frozen soil can be measured by time domain reflectometry. It has been shown that these can be combined to rapidly and accurately determine the dry range of the moisture characteristic. There are uncertainties at the wet end, but this is the region where traditional methods work well. Hence it is concluded that a combination of traditional moisture release methods for wet soil with freezing methods for dry soil will be the most efficient and accurate means for determining the moisture characteristic curve.