HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Bouma, J. Articles by Wösten, J. H. M. Search for Related Content PubMed Articles by Bouma, J. Articles by Wösten, J. H. M. Agricola Articles by Bouma, J. Articles by Wösten, J. H. M.

Flow Patterns During Extended Saturated Flow in Two, Undisturbed Swelling Clay Soils with Different Macrostructures¹

ABSTRACT

Large, undisturbed soil columns with an average height of 30 cm, a diameter of 25 cm, and with two different types of macrostructure were sampled in moist clay soil. Type 1 had vertical wormchannels and "rough" peds; type 2 had no worm channels and "smooth" peds. Flow patterns were characterized by repeatedly measuring K_sat and chloride breakthrough curves. Effective pore size distributions were calculated from the latter with the Klinkenberg procedure.

Initial chloride breakthrough was most rapid in soil columns of type 1 after displacement of < 1 vol. % of the initial water, whereas 3 vol. % was displaced in type 2. Rapid chloride breakthrough was associated with a high volume of immobile water (60 vol. % and 2 vol. % for types 1 and 2 respectively). These phenomena can be explained by the presence of relatively large, continuous pores (particularly in type 1), that occupy only a small volume, as was confirmed by micromorphometric analysis and calculations of effective pore diameters. Application of a gypsum crust on soil columns of type 1 erased the differences with type 2. Crusts induced pressure potentials of __5 mbar, thus excluding the largest pores only. Extended ponding and associated continued swelling of peds did not change flow phenomena in type 1; in type 2, K_sat, the volume of immobile water and the effective pore diameters gradually decreased. Equivalent pore diameters, calculated from the soil moisture characteristic, were quite different from the effective diameters and could not be used to independently predict the breakthrough curves. Direct measurement of the latter and empirical extrapolation to soils with identical texture, mineralogy, and macrostructure is recommended for field work because replicate columns, sampled in a large geographical area and with the two types of macrostructure, showed significantly different flow phenomena.

¹ Contribution from the Soil Survey Institute, Box 98, Wageningen, The Netherlands, in cooperation with the Dep. of Soils and Fertilizers, Agric. Univ. Wageningen.

² Soil Scientist and graduate Student, Dep. of Soil Physics. Soil Survey Institute, respectively.

Received for publication May 4, 1978. Accepted for publication September 20, 1978.

This article has been cited by other articles:

				M. H. Young, E. V. McDonald, T. G. Caldwell, S. G. Benner, and D. G. Meadows Hydraulic Properties of a Desert Soil Chronosequence in the Mojave Desert, USA Vadose Zone J., August 1, 2004; 3(3): 956 - 963. [Abstract] [Full Text] [PDF]

				C. Kjaergaard, T. G. Poulsen, P. Moldrup, and L. W. de Jonge Colloid Mobilization and Transport in Undisturbed Soil Columns. I. Pore Structure Characterization and Tritium Transport Vadose Zone J., May 1, 2004; 3(2): 413 - 423. [Abstract] [Full Text] [PDF]

				W. Bodhinayake, B. C. Si, and C. Xiao New Method for Determining Water-Conducting Macro- and Mesoporosity from Tension Infiltrometer Soil Sci. Soc. Am. J., May 1, 2004; 68(3): 760 - 769. [Abstract] [Full Text] [PDF]