Transformation of Phosphorus and Its Availability to Plants in Coal Mine Soils

Sarirullah, Mohammad (1989) Transformation of Phosphorus and Its Availability to Plants in Coal Mine Soils. PhD thesis, University of Glasgow.

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The work of this thesis is concerned with the study of some aspects of phosphorus cycling in coal mine soils. The introductory chapter presents a short review of some aspects of phosphorus behaviour in soil. The main emphasis has been given to phosphorus forms and their practical significance, reaction and interaction in soils, mobility and crop requirements. A short account of phosphorus behaviour and its problems in coal mine soils has also been discussed. Chapter 2 deals with the various methods and procedures adopted during the present study. Both routine published methods and methods developed to meet specific problems encountered with coal mine soils have been described. Although phosphorus is a thoroughly studied plant nutrient in agriculture, much remains to be learned about its status and behaviour in coal mine soils. Chapter 3 deals with the phosphorus status and chemical and biological turnover in coal mine soils. Thirty samples of widely varying properties were taken and various properties measured. All types of extractable phosphorus (acetic acid, anion exchange resin and sodium bicarbonate) measured in the waste material were very low. Carbon dioxide evolution and phosphorus turnover rates showed that a high level of carbon, but very little phosphorus, was turned over. Carbon mineralization correlated with soil pH. Due to either loss of phosphorus or very low mineralization rate, the effect of soil pH on phosphorus turnover was not pronounced. The present results support the contention that chemical immobilization of phosphorus can be substantial in these coal mine soils. The biological immobilization can also not be ignored. The generally low values of acid phosphatase activities measured in these soils also suggest that phosphorus mineralization may be slower on mine soils. The high values of adsorption maxima, calculated from Langmuir plots, in some soils highlight the great ability the material has for removing phosphate from solution. Phosphorus is the second most restrictive element to plant growth after nitrogen in coal mine soils. Chapter 4 discusses the problem of different levels of available phosphorus, crop response and the capacity of soil to fix phosphorus after cropping. A growth experiment under controlled conditions, in which varying levels of phosphorus fertilizers were added to five different coal mine soils, was set up. Since it was expected that either biological or chemical immobilization of phosphorus, or both, might play an important role in the lack of response of phosphatic fertilizers to crops in the coal mine soils, both acid phosphatase activities and adsorption maxima were also measured. Three rates of phosphorus, representing the addition of 0, 50 and 100 kg ha -1 as sodium dihydrogen phosphate were compared for both crop yield and phosphorus uptake by perennial ryegrass. The results showed that phosphorus deficiency is a major factor limiting plant growth in most of the coal mine soils. Lolium perenne can benefit from the addition of phosphorus. However, there is a danger that such an increase in phosphorus addition can cause phosphorus losses. Soils which did not show any phosphorus losses exhibited low adsorption maxima indicating low phosphorus fixation. pH and acid phosphatase activities did not show any relationship with crop response to phosphate fertilizer. The high amount of phosphorus mineralized in some soils might partly be due to high acid phosphatase activities. The poor correlations of acetic acid extractable phosphorus with phosphorus uptake and crop yield indicate that either acetic acid is extracting an unavailable pool due to low pH of coal mine soil or has limitations in the analysis of soils derived from different parent materials. Some coal mine soils contain partially weathered or unweathered materials which might play an important role in the poor acetic acid P-crop uptake relationship by exposure of new soil surfaces from which phosphate ions are not taken up by ryegrass. There is a great deal of controversy surrounding the effect of liming on both phosphorus supplying power and phosphorus extraction of highly weathered acid soils. A laboratory incubation experiment was carried out (Chapter 5) to study the effect of lime on both native and added phosphorus in two selected samples of coal mine soils with different properties. The effect of two extractants, namely acetic acid and ammonium fluoride, was also studied and compared. Three rates of phosphatic fertilizer, 0, 50 and 100 mg P kg-1 soil, were applied with and without lime. One level of lime representing the amount required to raise the pH of soil to 6.5 was applied as CaCO3. This study supported the contention that, in the majority of cases, lime induces no effect on phosphorus availability. However, in one soil, lime significantly increased the acetic acid extractable phosphorus. A brief, concluding chapter discusses some management practices in the light of the experimental results described previously.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Soil sciences, Biogeochemistry
Date of Award: 1989
Depositing User: Enlighten Team
Unique ID: glathesis:1989-77938
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 28 Feb 2020 12:09
Last Modified: 28 Feb 2020 12:09

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