Micromorphological study of slumping in a hardsetting seedbed under various wetting conditions

Bresson, L. M. and Moran, C. J. (2004) Micromorphological study of slumping in a hardsetting seedbed under various wetting conditions. Geoderma, 118 3-4: 277-288. doi:10.1016/S0016-7061(03)00212-X


Author Bresson, L. M.
Moran, C. J.
Title Micromorphological study of slumping in a hardsetting seedbed under various wetting conditions
Journal name Geoderma   Check publisher's open access policy
ISSN 0016-7061
Publication date 2004-01-01
Sub-type Article (original research)
DOI 10.1016/S0016-7061(03)00212-X
Volume 118
Issue 3-4
Start page 277
End page 288
Total pages 12
Place of publication Amsterdam
Publisher Elsevier Science Bv
Language eng
Subject 050205 Environmental Management
Abstract Slumping of hardsetting seedbeds upon wetting has not been extensively studied despite the likelihood that it determines the physical properties after drying. Slumping results from processes similar to those involved in crusting except that overburden pressure can dominate rather than rainfall kinetic energy. Only a few studies have dealt with the morphological description of slumping. To simulate different climatic and management conditions, repacked seedbeds of a hardsetting sandy-loam soil were subjected to a range of wetting conditions, e.g. capillary rise, immersion, and rainfall simulation. Slumping processes were characterized using qualitative and quantitative micromorphological observations of polished blocks and thin sections from resin-impregnated samples. A morphogenetical framework was proposed to help description of the complex associations of processes which can lead to structural collapse (crusting and slumping) on wetting. Three main stages were considered, i.e. aggregate disruption or abrasion, relocation of the released material, and compaction. In the hardsetting material studied here, structural collapse under slow wetting occurred at the bottom of cores due to aggregate coalescence under overburden pressure. Coalescence required aggregate cohesion being reduced by microcracking; therefore, it differed from the coalescence previously described in unstable silty loam soils where microcracking was not necessary for aggregates to coalesce. Macroporosity decreased most strongly under fast wetting due to physical dispersion and aggregate breakdown. Under simulated rainfall, compaction by raindrops could not be distinguish from aggregate breakdown. The role of overburden pressure and of rainfall kinetic energy remains to be stated; new data are required including measurement of total porosity in the initial, wet, and dry states. (C) 2003 Elsevier B.V. All rights reserved.
Keyword Agriculture, Soil Science
Aggregate Breakdown
Aggregate Coalescence
Compaction
Microcracking
Overburden Pressure
Surface Crusting
Structural Crust Formation
Macropore Structure
Size-distribution
Australian Soils
Strength
Classification
Collapse
Loamy
Soil Science
Q-Index Code C1

Document type: Journal Article
Sub-type: Article (original research)
Collections: Excellence in Research Australia (ERA) - Collection
Sustainable Minerals Institute Publications
 
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Created: Tue, 14 Aug 2007, 00:04:49 EST