Winter Soil Moisture Regime Monitored by the Time Domain Reflectometry Technique (TDR)

Abstract

Soil moisture, soil temperature, and frost depth have been monitored for two winters in cultivated soil, and, on monoliths, in the laboratory at temperatures well below the freezing point. Time Domain Reflectometry, being a non-destructive technique, has proved successful in showing the progress of frost and thaw fronts, of the considerable portion of water remaining unfrozen throughout the winter, and, of the redistribution of soil water that occurs between growing seasons.

Results emphazise the role of the diffuse electric double layer, partly in its relationships to hydraulic conductivity which, although lowered by factor of 10 to 100, never reaches zero in so called frozen soils. At temperatures of Scandinavian winters, in particular under a snowcover, it is shown that an un-broken liquid pathway exists all through the winter soil profile. The importance to frost heave is well-known; the present study emphazises also its importance to creep where it offers a deeper understanding of the slope movements of soil.