Measurement of exchangeable cations in saline soils

So, H.B., Kopittke, P. M., Menzies, N. W. and Bigwood, R. C. (2004). Measurement of exchangeable cations in saline soils. In: B. Sing, Supersoil 2004: 3rd Australian New Zealand Soils Conference. 3rd Australian New Zealand Soils Conference (Supersoil 2004), Sydney, Australia, (1-7). 5-9 December 2004.

Author So, H.B.
Kopittke, P. M.
Menzies, N. W.
Bigwood, R. C.
Title of paper Measurement of exchangeable cations in saline soils
Conference name 3rd Australian New Zealand Soils Conference (Supersoil 2004)
Conference location Sydney, Australia
Conference dates 5-9 December 2004
Proceedings title Supersoil 2004: 3rd Australian New Zealand Soils Conference
Place of Publication Gosford, Australia
Publisher The Regionals Institute
Publication Year 2004
Sub-type Fully published paper
ISBN 1 920842 26 8
Editor B. Sing
Start page 1
End page 7
Total pages 7
Collection year 2004
Language eng
Abstract/Summary The measurement of exchangeable cations in saline soils is limited by the difficulty in accurately separating soluble cations from exchangeable cations. A method is examined for saline soils in which exchangeable cations are calculated as the total extractable cations minus the concentration of soil solution (soluble) cations. In addition, a further two standard methods were investigated, one which assumes the total soil extractable cations are exchangeable, the other utilises a pretreatment to remove soluble salts prior to measurement of the remaining (exchangeable) cations. After equilibration with a range of sodium adsorption ratio (SAR) solutions at various ionic strengths, the exchangeable cation concentrations of two soils (Dermosol and Vertosol) were determined by these methods and compared to known values. The assumption that exchangeable cations can be estimated as the total soil extractable cations, although valid at low ionic strength, resulted in an overestimation of exchangeable Na and Ca concentrations at higher ionic strengths due to the presence of soluble salts. Pretreatment with ethanol and glycerol was found to effectively remove soluble salts thus allowing the accurate measurement of the effective cation exchange capacity (ECEC), however, dilution associated with the pretreatment process decreased concentrations of exchangeable Ca while simultaneously increasing exchangeable Na. Using the proposed method, good correlations were found between known and measured concentrations of exchangeable Na (Dermosol: y=0.873x and Vertosol: y=0.960x) and Ca (Dermosol: y=0.906x, and Vertosol: y=1.05x). Therefore, for soils with an ionic strength of approximately 50 mM (ECse 4 dS m-1) or greater (in which exchangeable cation concentrations are overestimated by assuming the total soil cations are exchangeable), concentrations can be calculated as difference between total extractable cations and soluble cations.
Subjects E1
300103 Soil Chemistry
770402 Land and water management
Q-Index Code E1
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Created: Thu, 23 Aug 2007, 19:37:12 EST