The Behaviour of Plant Nutrients in Colliery Spoil of Central Scotland

Lister, James Edward (1987) The Behaviour of Plant Nutrients in Colliery Spoil of Central Scotland. PhD thesis, University of Glasgow.

Abstract

The work of this thesis is concerned with the chemical analysis of coal waste of the Central Scottish Coalfield, treating this coal waste as a plant growth medium with the aim of rehabilitating it for agricultural use. There are numerous chemical and physical factors acting against plant growth and Chapters 2-4 highlight three of the main problems viz. high levels of trace elements, low phosphorus content and low levels of exchangeable cations. The physical properties of coal waste are outwith the scope of this thesis although they are discussed in Chapter 1. Chapter 1 describes the two methods of coal extraction, opencast and deep mining, the latter being the most commonly used in the United Kingdom, producing some 17.5 million tonnes of coal waste annually (at the present coal production rate) adding to that which has accumulated in the past, estimated in 1982 at 3,000 million tonnes covering 13,000 hectares of land. One of the main problems encountered in spoil reclamation is the heterogeneous nature of the material and the considerable differences in chemical and physical properties found between sites, each site requiring careful study at each stage of operation. Coupled with this are the changes which occur in the spoil on exposure, particularly the oxidation of iron pyrites (FeS2), producing sulphuric acid which threatens plant establishment and also attacks the spoil matrix. Chapter 2 examines the problem of high levels of available trace elements found in colliery spoil and their uptake by plants, five elements being chosen for study, namely Fe, Al, Mn, Cu and Zn, although there are many others which are limiting to plant growth. A comparison was made of the trace element content of perennial ryegrass (Lolium perenne) grown on a reclaimed spoil and an arable soil to determine the sites of requirement or deposition within the plant. A field trial was set up to determine the effects of addition of lime and organic amendments to spoil on the trace element content of the sward, results being presented for the first harvest taken after eleven weeks growth. Due to the short growing time no conclusions can be drawn from the organic amendment trial although the effects of trace element content on plant yield are discussed. After nitrogen, phosphorus is the element most restrictive to plant growth in colliery spoil. Chapter 3 discusses the problem of low levels of available phosphorus and the capacity of the spoil to fix phosphorus in an unavailable form through adsorption on hydrous oxides of iron and aluminium. A growth experiment under controlled conditions in which varying levels of lime and phosphorus fertilizer were added to three spoils showed that both spoil pH and phosphorus deficiency are major factors limiting plant growth. Chapter 4 discusses the cation exchange capacity and exchangeable base content of colliery spoil i. e. the ability of the material to hold cations in a form which may be released to the spoil solution for plant uptake and the levels of exchangeable Ca2+, Mg2+, K+ and Na+ found in a range of spoil samples. Results show that the amorphous iron and aluminium oxides in the spoil are adsorbed on exchange sites, while the amorphous manganese fraction, itself being negatively charged, may hold nutrient cations in an available form. Colliery spoil being a poor growth medium requiring the addition of high rates of fertilizers for plant growth may be reclaimed more successfully, if more expensively, by the use of a soil cover. Chapter 5 reviews the advantages of the use of soil in spoil reclamation based on evidence collected from 13 reclaimed sites in Central Scotland, these being described fully in Appendix II. This study shows that these advantages, however, may be greater if the nature of the underlying spoil was first considered, as the soil layer does not completely remove the plant from the effects of the spoil.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Organic chemistry, Biogeochemistry
• Date of Award: 1987
• Depositing User: Enlighten Team
• Unique ID: glathesis:1987-77675
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 14 Jan 2020 11:53
• Last Modified: 14 Jan 2020 11:53
• URI: https://theses.gla.ac.uk/id/eprint/77675