Reduction of hydraulic conductivity and loss of organic carbon in non-dispersive soils of different clay mineralogy is related to magnesium induced disaggregation

Zhu, Yingcan and Bennett, John McLean and Marchuk, Alla (2019) Reduction of hydraulic conductivity and loss of organic carbon in non-dispersive soils of different clay mineralogy is related to magnesium induced disaggregation. Geoderma, 349. pp. 1-10. ISSN 0016-7061

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Abstract

Irrigation water containing appreciable amount of magnesium (Mg) is increasingly used in farming. However, studies on the effect of Mg on soil permeability and structural stability are limited and the results are contradicting. In this study, four soils of different dominant clay mineralogy, specifically kaolinite, illite and montmorillonite, were used to investigate the effect of Mg on saturated hydraulic conductivity (Ksat), interaction with organic carbon and soil clay dispersion and to compare to the effect of Ca. The soils were packed in columns and leached with four groups of either Ca-Ca, Ca-Mg, Mg-Mg or Mg-Ca solutions at the successive concentrations of 0.5, 0.25, 0.1, 0.05, 0.025, 0.01, 0.005, 0.001 and 0.0001 M, and finally with deionised water. Ksat was measured and leachates were assessed for dissolved organic carbon (DOC) and dispersion as turbidity. The leached soils were tested for aggregate stability, mechanical dispersion and zeta potential. This study showed that Mg had a disaggregation effect on soil structural stability. As compared to Ca, Ksat on Mg treated cores were lower over a wide range of concentrations, desorption of DOC and turbidity from Mg clay surface was higher, although the dispersion in leachates was insignificant under both Mg and Ca treatments. The effect of Mg treatment was more pronounced on smectic and illitic soils. The decrease in Ksat was related to Mg induced disaggregation, due to intra-crystalline swelling and/or the inter-crystalline swelling in Mg treated soil clays.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Files associated with this item cannot be displayed due to copyright restrictions.
Faculty/School / Institute/Centre: Current - Institute for Life Sciences and the Environment - Centre for Sustainable Agricultural Systems (1 Aug 2018 -)
Faculty/School / Institute/Centre: Current - Institute for Life Sciences and the Environment - Centre for Sustainable Agricultural Systems (1 Aug 2018 -)
Date Deposited: 02 Jul 2020 04:19
Last Modified: 20 Jul 2020 03:21
Uncontrolled Keywords: Magnesium; Calcium; Saturated hydraulic conductivity; Dissolved organic carbon; Turbidity
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
Socio-Economic Objectives (2008): D Environment > 96 Environment > 9614 Soils > 961402 Farmland, Arable Cropland and Permanent Cropland Soils
Identification Number or DOI: 10.1016/j.geoderma.2019.04.019
URI: http://eprints.usq.edu.au/id/eprint/38511

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