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ABSTRACT
Soil water characteristic curves are routinely determined by the pressure plate and pressure membrane techniques. Similar curves can be derived from pore size distribution curves obtained by the mercury intrusion porosimeter technique. Mercury is forced under pressure into previously oven-dried and evacuated samples. The applied pressure is increased in discrete steps and the volume of pores intruded between pressure steps is obtained. Equivalent pore sizes corresponding to the applied pressures are calculated with the pressure of displacement equation. This technique allows analysis of many samples per day and has therefore an advantage over standard methods.
Soil water characteristic curves of eight soils ranging in clay content from 0 to 57% were determined by the pressure plate and pressure membrane technique and compared with similar curves derived from mercury intrusion data. Results obtained by the two techniques agreed well for soils which do not shrink or swell with changes in water content, but not for samples with swelling clays.
1 Technical Paper 3127, Oregon Agr. Exp. Sta., Corvallis. Contribution from the Department of Soil Science. Research supported by matching fund project B-001-ORE of the Office of Water Resources Research, USDI.
2 Research Assistant, Professor, and former Research Associate, respectively, Oregon State University, Corvallis, Oregon 97331. Present address of Dr. DeBacker: Laboratoire d'Hydrodynamique des Sols, 92 Avenue Cardinal Mercier, Heverlee (Louvain), Belgium.
Received for publication July 17, 1971. Accepted for publication November 16, 1971.
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