Pedosphere 17(4): 436--444, 2007
ISSN 1002-0160/CN 32-1315/P
©2007 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Soil water hysteresis at low potential |
L. PRUNTY and J. BELL |
| Department of Soil Science, North Dakota State University, Fargo, ND 80105 (USA). E-mail: lprunty@ndsuext.nodak.edu |
| ABSTRACT |
| Knowledge of the soil water characteristic curve is fundamental for understanding unsaturated soils. The objective of this work was to find scanning hysteresis loops of two fine textured soils at water potentials below wilting point. This was done by equilibration over NaCl solutions with water potentials of -6.6 to -18.8 MPa at 25℃. When cycled repeatedly through a series of potentials in the range noted previously both soils exhibited a hysteresis effect. The experimental differences in water content between the drying and wetting soils at the same water potential were much too large to be accounted for by failure to allow sufficient time to attain equilibrium as predicted by the exponential decay model. The wetting versus drying differences were relatively small, however, at only 4 mg g-1 or less in absolute terms and about 3% of the mean of wetting and drying, in relative terms. Hysteresis should be a consideration when modeling biological and physical soil processes at water contents below the wilting point, where small differences in water content result in large potential energy changes. |
| Key Words: adsorption, dry soil, equilibration, rnatric potential, soil water characteristic |
| Citation: Prunty, L. and Bell, J. 2007. Soil water hysteresis at low potential. Pedosphere. 17(4): 436-444. |
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