Re-examining the flocculating power of sodium, potassium, magnesium and calcium for a broad range of soils

Zhu, Yingcan ORCID: and Ali, Aram ORCID: and Dang, Aaditi and Wandel, Andrew P. ORCID: and Bennett, John McLean (2019) Re-examining the flocculating power of sodium, potassium, magnesium and calcium for a broad range of soils. Geoderma, 352. pp. 422-428. ISSN 0016-7061


Cation ratio of soil structural stability (CROSS) and exchangeable dispersive percentage (EDP) have been recently proposed to replace the traditional sodium absorption ratio (SAR) and exchangeable sodium percentage (ESP) for predicting soil structural stability, in conjunction with the electrolyte concentration. Both CROSS and EDP incorporate the dispersive effects as coefficients transforming K and Mg effects to equivalent Na, and flocculative coefficient transforming Mg effect to equivalent Ca. However, these coefficients are derived from the flocculating power of Na, K, Mg and Ca based on a limited number of soil clays. This study re-examines the flocculating power for a broad range of soil clays by analysing their critical flocculation concentrations (CFCs). Soil clays from 17 contrasting soils were separated and chemically treated into Na, K, Mg and Ca homoionic clays. Within the same cation treatment, there were significant differences among the measured CFC values, which can be related to their different clay mineralogy and co-existing materials in soil clays. The dispersive coefficients of K and Mg, as well as the flocculative coefficient of Mg, were seen to vary substantially in respect to the generalised values used in CROSS and EDP. The absolute errors between the specified CROSS and generalised CROSS as well as the specified EDP and generalised EDP have been calculated for the 95th percentile of possible cation concentrations. In terms of CROSS, the dispersive coefficient a[K] and flocculative coefficient b[Mg] both contribute to the absolute error, with a[K] having a greater influence than b[Mg]. In terms of EDP, the dispersive coefficient a[K] played the dominant role in causing absolute error between the specified EDP and generalised EDP, while the role of dispersive coefficient c[Mg] was not significant. The outcome of this work indicates that the soil-specific coefficients should be used to minimise the possibility of undue soil structural degradation, while the generalised coefficients are only applicable to a small range of outcomes.

Statistics for USQ ePrint 37516
Statistics for this ePrint Item
Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Permanent restricted access to Published version, in accordance with the copyright policy of the publisher.
Faculty/School / Institute/Centre: Current - Institute for Life Sciences and the Environment - Centre for Sustainable Agricultural Systems (1 Aug 2018 -)
Faculty/School / Institute/Centre: Historic - Faculty of Health, Engineering and Sciences - School of Mechanical and Electrical Engineering (1 Jul 2013 - 31 Dec 2021)
Date Deposited: 17 Dec 2019 07:06
Last Modified: 17 Jan 2020 02:56
Uncontrolled Keywords: flocculating power, cation ratio of soil structural stability (CROSS), exchangeable dispersive percentage (EDP), sodium adsorption ratio (SAR), exchangeable sodium percentage (ESP), dispersion
Fields of Research (2008): 05 Environmental Sciences > 0503 Soil Sciences > 050304 Soil Chemistry (excl. Carbon Sequestration Science)
05 Environmental Sciences > 0503 Soil Sciences > 050399 Soil Sciences not elsewhere classified
Fields of Research (2020): 41 ENVIRONMENTAL SCIENCES > 4106 Soil sciences > 410604 Soil chemistry and soil carbon sequestration (excl. carbon sequestration science)
41 ENVIRONMENTAL SCIENCES > 4106 Soil sciences > 410699 Soil sciences not elsewhere classified
Socio-Economic Objectives (2008): D Environment > 96 Environment > 9614 Soils > 961402 Farmland, Arable Cropland and Permanent Cropland Soils

Actions (login required)

View Item Archive Repository Staff Only