Vermicompost and gypsum amendments improve aggregate formation in bauxite residue

Zhu, F., Jingtao, H., Xue, S., Chuan, W., Qiongli, W and Hartley, W. (2017) Vermicompost and gypsum amendments improve aggregate formation in bauxite residue. Land Degradation & Development.

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Improving aggregate formation and stability of bauxite residue is essential for the development of a soil on the residue. Effects of gypsum and vermicompost on related chemical and physical conditions of bauxite residue were studied in a laboratory incubation experiment. Addition of gypsum at 2% and 4% w/w reduced pH and exchangeable sodium percentage, whilst increasing exchangeable calcium content. Addition of vermicompost reduced bulk density, whilst significantly increasing porosity and total organic carbon. Vermicompost had a positive effect on the formation and stabilization of water-stable aggregates in the residue, whilst gypsum was more beneficial to silt-sized microaggregate flocculation. Amendments also enhanced the erosion resistance of bauxite residue. Furthermore, wet sieving using the modified Le Bissonnais’ (LB) method revealed that in comparison to differential clay swelling and mechanical breakdown, slaking was the major disaggregation mechanism of residue aggregates. The combination of gypsum and vermicompost converted the residue from a sheet-like structure to a granular macroaggregated structure, whilst converting microaggregates from a grain to a granular or prismatic structure. The findings of this work suggest that application of gypsum and vermicompost to bauxite residue may directly influence aggregate size distribution and its micromorphology, resulting in the improvement of both aggregate stability and structure.

Item Type: Article
Additional Information: This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.
Keywords: Bauxite residue; gypsum; vermicompost;aggregate formation aggregate stability
Divisions: Crop and Environment Sciences (to 31.07.20)
Depositing User: Ms Kath Osborn
Date Deposited: 29 Mar 2017 15:22
Last Modified: 08 Jul 2020 14:14

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