A classification of soil aggregates based on their coherence in water

Abstract

Soil aggregates have been divided into seven classes by observing the coherence of the clay fraction after reacting aggregates with water. The reactions used were: immersion of dry aggregates in water, immersion of wet remoulded aggregates in water, and suspension of aggregates in water. One further class was distinguished by the presence of carbonate. Illite and montmorillonite clays were modified so as to exhibit the physical properties of some of the aggregate classes. The results with the clays were then used to explain the characteristic properties of aggregates derived from a wide variety of soils in the various classes. For example, class 2 aggregates show partial dispersion when placed, dry, in water. The minimum percentage of exchangeable sodium present in aggregates of this class was equal to that required for dispersion of the dry Na/Ca-clays immersed in water. Examples are given of where the detection of dispersion from aggregates can be useful in the field. As only simple tests are used, the proposed method of classification can be easily carried out under field conditions.

Dispersion behavior of soils from reclaimed lands with poor soil physical properties and their characteristics with special reference to clay mineralogy

“…Thus, it was surprising to note that H8 exhibited a very high dispersibility under the field conditions in spite of the small amount of charges. Regarding the dispersion behavior of illite, however, Emerson (1967) pointed out that a relatively small specific surface area of illite allowed water molecules to penetrate around the particles in the suspension, and as a result the dispersibility of illite was sometimes higher than that of montmorillonite.…”

Revised test protocols for the identification of dispersive soils

“…An assessment of the literature has found that most researchers appear to misquote Emerson's (Emerson 1964;Emerson 1967) work and use his findings incorrectly. There have been many cases in which the method has been misinterpreted with regard to variables such as moisture content and dispersing medium (Heinzen & Arulanandan 1977;Bell & Maud 1994;Walker 1997;Bell & Walker 2000).…”

Evaluation of soil structure using participatory methods in the semiarid region of Brazil

“…The methodology proposed by Emerson (1967) and Cerda (1998) was applied with no adaptations. Ten aggregates of 10 mm were put in 200 mL of water to evaluate its dispersion after 12; 24 and 36 hours, considering the scale: 0: no dispersion and aggregates completely stable; 1: dispersion of some particles, milkiness close to the aggregates; 2: Aggregates partly dispersed or divided into different smaller aggregates; 3: Considerable dispersion with most of the aggregates have been dispersed and milkiness very intense; 4: Total dispersion.…”