An Investigation of the Subsoil Component of a Constructed Mine Soil
Mcsweeney, Kevin
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https://hdl.handle.net/2142/71588
Description
Title
An Investigation of the Subsoil Component of a Constructed Mine Soil
Author(s)
Mcsweeney, Kevin
Issue Date
1984
Department of Study
Agronomy
Discipline
Agronomy
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Agronomy
Abstract
The objective of this study was to identify and describe soil structural patterns and rooting behavior in a reclaimed mine soil. The soil chosen for this study consists of approximately 40 cm of topsoil (A horizon) material placed over approximately 150 cm of a blend of B horizon, mixed paleoloesses, Sangamon paleosol and Illinoian till.
A distinct artificial structure consisting of rounded discrete aggregates loosely compressed together was characterized and defined. The structure was attributed to the specific mining and reclamation practices used at this site rather than natural soil forming processes. The structure was most prevalent in zones of the subsoil not subject to compaction and was typically associated with profuse rooting.
Large thin sections (6.5 x 7.0 cm) were made from soil samples collected from the subsoil. The samples were impregnated with carbowax prior to sectioning. The thin sections were then electro-optically analyzed using a Quantimet 720. This provided a detailed appraisal of porosity variation within the subsoil. The variation in porosity was attributed to both differences in the inherent porosity of individual materials and compaction. Compaction was most severe in places overriden by bulldozers during the selective grading of the subsoil. However, the porosity of the upper part of the subsoil (0-24 cm) was much less than that below. This broad scale reduction in porosity was attributed not only to selective grading but also to consolidation in response to overburden pressure and shrinkage upon drying. Despite the largely compacted nature of the upper part of the subsoil, primary roots were able to penetrate this zone largely through desiccation cracks and interaggregate pores. Extension of the primary roots into the less compact materials below was typically coupled with a marked increase in root development. These subsoils have a much greater potential for root exploitation than those with the massive physical condition which is found in many constructed mine soils.
An attempt was also made to quantitatively evaluate elemental distribution between corn roots and each of the four major components of the subsoil mix, using scanning electron microscopy in conjunction with X-ray analysis. Specimen preparation suitable for this technique was not achieved.
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