Characterizing Nonrigid Aggregated Soil–Water Medium Using its Shrinkage Curve

Abstract

The properties of the soil-water medium are presented in the literature independent of its internal organization and operation. The objective of this study is to develop and test a conceptual model that used a continuously measured shrinkage curve (Se) to describe the functional organization of the soil-water medium. In this model, two functional porosities (micro and macro) are delineated and quantified by the Se. In addition, the equilibrium for four functional water pools is represented and parameterized by the Se. A set of eleven parameters was found necessary to model the seven phases of the se and to describe the corresponding soil hydrostructural changes. A method to accurately obtain the parameters of this model by a specific analysis of the continuously measured se is demonstrated. Examples of continuously measured and modeled SCS according to the pedostructure model (PS) are presented and discussed.

Antecedent soil moisture affecting surface cracking of a Vertisol in field conditions

“…On one hand, shrinkage may have started with a low rate similar to shrinkage rates exhibited in groups 1 and 2 then followed an increasing shrinkage rate of the line fitted to all measured data in the group of largest antecedent soil moisture. The phase with small shrinkage rate at the beginning of desiccation may correspond to the curvilinear phase between the maximum swelling and the macroporosity limit in the structural phase identified in well structured soil cores, and was demonstrated by several shrinkage curve studies (Braudeau et al, 2004;Boivin et al, 2004;Boivin, 2007;Milleret et al, 2009). On other hand, shrinkage in 1993, 1997 and 1998 may have individual linear shrinkage paths.…”

A framework for soil-water modeling using the pedostructure and Structural Representative Elementary Volume (SREV) concepts

“…The S-matrix of a soil material "is the material within the simplest (primary) peds, or composing apedal soil materials, in which the pedological features occur; it consists of plasma, skeleton grains, and voids that do not occur in pedological features other than plasma separations." Braudeau et al (2004) completed this morphological definition of primary peds with a hydro-functional definition based on the determination of an air entry point in the clayey plasma using the shrinkage curve that was continuously measured by the apparatus detailed in Braudeau et al (1999). They introduced the term "pedostructure" which is the assembly of primary peds that is represented by two nested and complementary pore systems named as micropore and macropore corresponding respectively to the intra and inter primary ped pore space.…”

“…According to the new developments in thermodynamics of the soil medium presented here above, the pedostructure shrinkage curve already modeled in Kamel using equations developed by Braudeau et al (2004) were updated with the thermodynamic equations of W eq mi and W eq ma . This update of the shrinkage curve is described in Supplementary Material, Appendix 2.…”

“…However, none of these models consider the soil medium as a structured medium with aggregates, and thus, they are unable to take into account the notion of primary peds, which represent the first level of organization of the primary particles into aggregates (Brewer, 1964), and the notion of pedostructure (Braudeau et al, 2004) which is constituted by their assembly. Consequently, the swelling-shrinkage properties of the primary peds within the soil structure that were quantified by Braudeau and Bruand (1993), and also the resulting hydro-structural properties of the soil medium (Braudeau et al, 2004(Braudeau et al, , 2005Braudeau and Mohtar, 2006), cannot be considered and modeled in the current agro-environmental modeling.…”

“…Consequently, the swelling-shrinkage properties of the primary peds within the soil structure that were quantified by Braudeau and Bruand (1993), and also the resulting hydro-structural properties of the soil medium (Braudeau et al, 2004(Braudeau et al, , 2005Braudeau and Mohtar, 2006), cannot be considered and modeled in the current agro-environmental modeling.…”