Threshold electrolyte concentration for dispersive soils in relation to CROSS

Marchuk, Alla and Rengasamy, Pichu and McNeill, Ann (2012) Threshold electrolyte concentration for dispersive soils in relation to CROSS. In: Joint Australian and New Zealand Soil Science Conference (SSA 2012): Soil Solutions for Diverse Landscapes, 2-7 Dec 2012, Hobart, Australia.

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Sodium salts tend to dominate salt-affected soils and groundwater in Australia; therefore, sodium adsorption ratio (SAR) is used to parameterise soil sodicity and the effects of sodium on soil structure. However, some natural soils in Australia, and others irrigated with recycled water, have elevated concentrations of potassium and/or magnesium. Therefore, there is a need to derive and define a new ratio including these cations in place of SAR, which will indicate the dispersive effects of Na and K on clay dispersion, and Ca and Mg on flocculation. Based on the differential dispersive effects Na and K and the differential flocculation powers of Ca and Mg, we propose the concept of 'cation ratio of soil structural stability' (CROSS), analogous to SAR. This paper also gives the results of a preliminary experiment conducted on three soils varying in soil texture on hydraulic conductivity using percolating waters containing different proportions of the cations Ca, Mg, K, and Na. The relative changes in hydraulic conductivity of these soils, compared with the control treatment using CaCl2 solution, was highly correlated with CROSS. Clay dispersion in 29 soils treated with irrigation waters of varying cationic composition was highly correlated with CROSS rather than SAR. It was also found that CROSS measured in 1:5 soil/water extracts was strongly related to the ratio of exchangeable cations. These results encourage further study to investigate the use of CROSS as an index of soil structural stability in soils with different electrolytes, organic matter, mineralogy, and pH.

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Item Type: Conference or Workshop Item (Commonwealth Reporting Category E) (Poster)
Refereed: No
Item Status: Live Archive
Additional Information: No evidence of copyright restrictions preventing deposit.
Faculty / Department / School: Historic - Faculty of Engineering and Surveying - Department of Agricultural, Civil and Environmental Engineering
Date Deposited: 03 Nov 2014 04:00
Last Modified: 15 Sep 2017 04:00
Uncontrolled Keywords: exchangeable magnesium; exchangeable potassium; irrigation; sodicity; soil structure
Fields of Research : 09 Engineering > 0907 Environmental Engineering > 090702 Environmental Engineering Modelling
05 Environmental Sciences > 0503 Soil Sciences > 050304 Soil Chemistry (excl. Carbon Sequestration Science)
07 Agricultural and Veterinary Sciences > 0799 Other Agricultural and Veterinary Sciences > 079901 Agricultural Hydrology (Drainage, Flooding, Irrigation, Quality, etc.)
Socio-Economic Objective: D Environment > 96 Environment > 9614 Soils > 961499 Soils not elsewhere classified

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