3 Feigenbaum et al. 1981; Strömberg and Banwart 1999. Particle size was shown to
greatly determine the effects of basalt dust on soil properties Gillman et al. 2001, 2002. Milling methods that produce superfine particles of minerals with enhanced
chemical reactivity have been evaluated for industrial uses by several workers, including Garcia et al. 1991, Sugiyama et al. 1994, and Suraj et al. 1997. These
milling methods also have been employed to improve the fertilizer effectiveness of several silicate minerals Harley 2002 and phosphate minerals Lim et al. 2003.
Further evaluation of high-energy milling as a method for manufacturing SRFs, including the use of reactive additives to enhance fertilizer effectiveness, is proposed
and has been evaluated in this thesis. In addition, soil properties that affect the dissolution of SRFs in the soil were identified. These properties may be appropriate
indicators for soil testing to evaluate the potential for use of SRFs for specific soils and plant species.
1.2. The Objectives of Research
The main hypotheses of this research are that 1 high-energy milling affects several physicochemical properties of silicate rocks and increases the release of
plant nutrient elements from SRFs and 2 soil properties affect the dissolution of SRF in the soil. To evaluate these hypotheses, several experiments were carried out
with the following main objectives. 1. To identify the effects of the condition and duration of high-energy milling of
silicate rocks variously combined with reactive additives on the physicochemical properties of mafic basalt and dolerite and K-rich felsic
gneiss and K-feldspar rocks. 2. To identify the dissolution characteristics of the milled rocks in a dilute organic
acid to provide a simple method for predicting dissolution of the milled rocks in soils.
3. To identify soil properties that influence the dissolution of SRFs in soils. 4. To measure the agronomic effectiveness of ground mafic basalt and dolerite
and felsic gneiss and K-feldspar rocks for plants grown on several soils.
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1.3. Organisation of
the Thesis
Following the above objectives, the main content of this thesis is divided into 6 chapters including this chapter. Chapter 2 describes the milling methods used in
this research and the physicochemical characteristics of the milled rocks. Dissolution of the milled rocks in a dilute organic acid is described in Chapter 3, and
dissolution in soil is discussed in Chapter 4. Chapter 5 describes a glasshouse experiment that measured the agronomic effectiveness of milled mafic and felsic
rocks as fertilizers. A summary of research findings, their limitations and recommendations for future research are provided in Chapter 6, followed by the lists
of references and appendices. Tables and figures are placed within the corresponding text.
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Chapter 2
EFFECTS OF MILLING TIME, CONDITIONS, AND REACTIVE ADDITIVES ON THE CHARACTERISTICS OF SILICATE ROCKS
2.1. Introduction
An effective method to accelerate the release of nutrients from SRFs to soil solution is high-energy milling that produces superfine reactive particles. Many
workers Gasalla et al. 1987; Kühnel and Van der Gaast, 1989; Garcia et al. 1991; Sugiyama et al. 1994; Aglietti 1994; Suraj et al. 1997; Uhlík et al. 2000 have
reported that high-energy milling has major effects on several physicochemical properties of minerals and rocks. High-energy milling may destroy the structural
order of minerals and increase the effective surface area, both effects will increase the reactivity of minerals. For example, Aglietti 1994 showed that dry milling of
talc increased CEC and the amount of Mg dissolved in water. High-energy milling accelerated nutrient release from several silicate minerals Harley 2002 and rock
phosphates Lim et al. 2003 in the soil. Too intensive milling, however, may cause agglomeration or sintering of fine particles resulting in a decrease of the effective
surface area. Agglomeration is due to a number of processes including exposed hydrogen ion bonding of surface hydroxyl groups on the fine particles,
agglomeration may be avoided by immersing the material in a polar liquid during milling Veale 1972, e.g., wet milling in H
2
O Reay 1981; Harley 2002 or in hydrocarbons including alcohol Papirer and Roland 1981. The addition of
potentially reactive additives, such as NaCl and KCl, to eliminate agglomeration and to supply additional plant nutrients may be beneficial has not been investigated for
silicate rocks. This chapter describes the results of investigations of the effects of milling methods including milling time and condition and the use of NaCl and KCl
additives on several physicochemical characteristics of mafic basalt and dolerite and felsic gneiss and K-feldspar rocks.
The specific objectives of the research described in this chapter are to identify 1 the effects of milling time and condition wet and dry and 2 the
effects of adding NaCl, KCl, and K-feldspar during the milling process on several physicochemical characteristics of the silicate rocks.
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2.2. Materials and Methods
