Approximately 6,200 square miles (16,000 square kilometers) of Sarawak, Malaysia, were mapped at 1:125,000 scale, the Area including portions of the coastal swamp plain, the interior highlands, and the intervening lower upland zone in which population and development are largely concentrated. Red-Yellow Podzolic Soils (mainly Dystropepts or Cambisols, and their shallow associateB) are dominant in the uplands and are mainly derived from sedimentary rocks. Terrace Podzols (Humods; Podzols) are important in many swamp fringe tracts. Deep Organic Soils (Fibrists; Dystric Histosols) mantle much of the coastal swamp zone with Gley Soils (Aquents; Fluviso1s) in estuarine and delta tracts. Silication and loss of clay from the upper subsoil are among the processes evident in upland soils but clay il1uviation is slight in most profiles examined. Other soil processes involved in upland areas include layering of subsoil materials' through slope creep and homogenisation through faunal disturbance. The difficulties of applying quantitative classifications to such soils is discussed and the continued use of traditional genetic groupings is supported. Correlations are made with the USDA and FAO classifications and with others regional systems. A proposed classification is developed for the Area's soils, using Groups based on the Thorp and Smith divisions (with some redefinition) and employing Families and Series defined with the requirements of a practical operational classification in mind. These requirements in a Sarawak context are discussed. The study is supported by soil and other maps, by data on sample profiles representing the main Soil Series of the Area, and by discussions of the soil pattern in relation to landform history in the Area and to the agricultural landscape now developed on it

Investigation has been made into the properties of Red Soils in West Java, Indonesia, selected from two different parent materials. Profiles P. Tb and P. Rb are derived from dacitic tuff and P. Js from pumice volcanic ash, both of which are acid in character. Profiles L. Km, L. Dr and L. Pk are derived from andesitic to basaltic volcanic ash, intermediate to basic in character. For comparison, soils from each group of parent materials were selected to be representative of areas of different climate, ranging from two annual dry months, to no dry month in the year. This study area is reviewed in chapter one. Chapter two discusses the factors and processes of soil formation in the tropics relevant to the soils studied. Chapter three discusses some characteristics of Latosolic and Podzolic soils, criteria for distinguishing them and their position in the Indonesian National Classification system (INCS). Soil clay fractions were extracted by several different selective dissolution methods: Na2CO3 (cold), 0.5 M NaOH (2.5 min boil), IM potassium pyrophosphate and dithionite-citrate-bicarbonate. Extraction enhanced the intensity of X-ray diffraction peaks and clarified identification of some minerals that were difficult to distinguish in the untreated clay. The effect was much more pronounced in the Latosolic than inthe Podzolic soils, mainly as a result of the different characteristics of the weathering products of these two groups of soil. Chapter four discusses some previous work that has been carried out in connection with selective dissolution analysis and includes some important new thoughts about microcrystalline minerals. Chapter five describes the methods that have been used in this study. They include particle size analysis, soil reaction (pHH20 and pHKCI), cation exchange properties, total nitrogen and carbon, selective dissolution analysis of clays by several different treatments, X-ray and thermal analyses and micromorphological observations. The principal results of this study are as follows: (i) The physical characteristics of the soils are mostly determined by the parent materials. Micromorphological examination substantiates this by showing the difference in the properties of the clay in these two groups of soils: Latosolic soils contain clay with the properties of flocculated paste; in Podzolic soils the clay is similar in nature to a deflocculated paste(ii) Climate in the study area exerts considerable control over weathering and leaching and determines the chemical properties of the soils. t. iii) In the study area climate and parent material seem to play the most important role in determining the properties of the soils studied. Civ) Microcrystalline and poorly ordered material in the clay fraction are more abundant in Latosolic than in Podzolic soils. Kaolinite is the most abundant clay mineral in profiles P. Tb, P. Rb, L. Km; its degree of crystallinity is greater in Podzolic soils. Other common minerals are (meta) halloysite in profiles P. Dr and P. Js and smectite in profile P. Js. Minor amounts of 2: I and interstratified minerals occur in most soils. Proposals for the improvement of soil classification are suggested: (i) The soils should be classified on the basis of the parent material. (ii) Since CEC is one of the best parameters to illustrate the stage of weathering of these soils it should be used to differentiate perhaps at the group level. Thus, the position of this factor is one level below the position of parent material. (iii) Soil chemical characteristics relate well to the climatic variation in the area. It is suggested that these characteristics should be considered at a lower level than CEC. This lower level should have a close relationship with soil fertility and so, with agricultural practice. The results of this study suggest that further detailed investigation on "Red Soils" in Indonesia, should be carried out on the same lines as here. The aim should be to establish one "Indonesian National Classification System" that is relevant to the conditions, economics and purposes of the country

Rice is the staple food for nearly one half of the ever growing world's population. Phosphorus (P) deficiency commonly constrains crop productivity on a large area of arable land worldwide. P fertilizer is a finite resource and an expensive input, so it must be used efficiently. The main objective of this study was to investigate plant and soil P interaction in P deficient conditions and understand plant mechanisms that could enhance P uptake efficiency throughout two main research approaches: Firstly, investigating plant and soil microbes' interaction that promotes plant growth in Plimited conditions. Secondly, evaluating the P uptake efficiency of a number of rice genotypes in a high throughput screening systems in order to understand genotypic variations in P uptake mechanisms. The genotypes used were genotyped for the allelic variation in the Pup1 locus and the effect of this QTL on the plant growth was also investigated. In an experiment investigating the influence of soil microbes on rice growth in P deficient conditions, an experimental system where pots were filled with a mix of 95% low P Insch subsoil and 5% Insch topsoil, where the subsoil was sterilized by autoclaving and the top soil was either sterilized or live. Non-autoclaved (live) topsoil caused a significant increase in shoot dry weight (SDW) for IAC 25 compared to autoclaved soil while the opposite was true for Azucena suggesting that the presence of soil microbes is needed for IAC 25 to access soil-bound P under P-limiting condition while for Azucena it is not. Most importantly, a very strong cultivar x treatment interactions on almost all growth parameters and elements in the shoot except for Mn were found. In a dose experiment investigating whether there is a general toxic effect for autoclaving Insch topsoil being used in this study on the growth of IAC 25, a strong positive correlations of plant growth parameters with the percentage of sterile topsoil vi levels were observed indicating that the autoclaved topsoil was not toxic. The influence of soil wash (distilled water added to the soil then extracted) and different types of soil as sources of inocula on the plant growth of rice cultivars were also studied. Soil wash inoculation did not affected plant growth but soil inocula increased the biomass of all rice cultivars (Azucena, IAC 25 and Lemont) tested suggesting that if it is microbes that are important they must be remaining in the soil and are not transferable by washing. Two autoclaved soils did not behave similarly in terms of affecting plant growth of rice cultivars (Azucena and IAC 25). Moreover, the live treatment of a new soil stimulated the growth of both cultivars and the cultivar x treatment interaction that was found in earlier experiment was lost with the use of this new soil. The implication is that the cultivar by autoclave treatment interaction is soil specific. The fluctuating results between the experiments indicate that it is unlikely that such studies can be extended into plant genetics. So, the second approach of the study focused on examining simpler plant/soil P interaction in P limiting conditions. A 25/75% subsoil/sand mix was determined as a P deficient and used to screen 30 rice genotypes in two experiments: the first when watered with Yoshida's nutrient solution (YNS) either with (YNS+P) or without P (YNS-P) to assess whether rice genotypes differ in extracting P added in liquid form while the second was designed to test if shallow and deep-rooted genotypes differ in extracting P present in soil by using rock phosphate in three treatments: when rock P was absent or embedded either in a shallow 10 cm layer or distributed homogenously in soil mix. For both experiments, P treatment x genotype interaction was significant on SDW. On average, YNS-P treatment significantly reduced the SDW for genotypes compared to that of plants grown in YNS+P treatment while the addition of rock phosphate greatly stimulated plant growth where SDW of plants grown in homogenous P and shallow P significantly outgrew vii those in zero P treatment. In both experiments, rice from the aus subgroup grown in -P treatment accumulated significantly more SDW than indica and japonica genotypes. In -P treatment, the genotypes that accumulated higher SDW relative to the others were Black Gora, Rayada, Kasalath, Azucena, IAC 25, Dom Sufid, Aux1Wild type, FR 13A and especially Sadu Cho. In the rock phosphate experiment, both P treatment and genotype affected RDW and root/shoot ratio significantly. Most importantly, two root angle traits (the mean root direction and the weighted average of the unsigned root angles) measured in rhizotrons were correlated with the relative SDW in shallow P (SDW in shallow P/SDW in zero P) slightly stronger than with relative SDW in homogenous P (SDW in homogenous P/SDW in zero P) indicating that the relationship between plant growth and root distribution with depth was altered by the distribution of rock phosphate in soil. In both experiments, the presence of Kasalath alleles in the Pup1 QTL significantly increased SDW of the genotypes. However, some genotypes, especially Dom Sufid and Sadu Cho performed well in these experiments despite lacking the Pup1 allele suggesting that Pup1 QTL is not the only determinant for tolerance to P deficiency. The system appears to be suitable for high throughput screens of rice genotypes.

The International Conference on Soil Mechanics and Foundation Engineering in 1936 was perhaps the first international forum which brought unsaturated soil problems to the attention of geotechnical engineers. Since then, the understanding of unsaturated soil behaviour has been improved considerably. The theory for the volume change and shear strength behaviour of unsaturated soils has now developed to the point of potential application in geotechnical practice. A complete understanding of the volume change behaviour of an unsaturated soil requires a knowledge of volumetric deformation moduli on four state planes. These moduli must be determined in either a direct or indirect manner in order to solve practical problems involving volume change, moisture movement, bearing capacity and slope stability analysis. The measurement of these moduli generally requires modification to conventional laboratory equipment. The solution of unsaturated soil problems would be greatly facilitated if the relationships between the various moduli were known. Then it would be possible for all moduli to be determined by a few established conventional soil tests. The main objective of this dissertation is to develop and measure the relationships between the various volume change moduli. The study began with a literature review on the volume change constitutive relations for the soil structure and water phase of an unsaturated soil. Attempts were made to gather information pertinent to the relationships between different moduli. The theory chapter started with an examination of the most acceptable form for the soil structure and water phase constitutive surfaces on both arithmetic and semi-logarithaic scales. Approximate semi-logarithmic constitutive surfaces were then proposed. The geometry of the approximate semi-logarithmic constitutive surfaces is used to relate the moduli associated with a particular phase (i.e., the soil structure or water phase). When a soil. is saturated, the soil structure and water phase moduli with respect to the logarithm of net total stress are related by the relative density, Gs' of the soil. The inter-relationship of the three remaining moduli was then studied. A laboratory test program was designed to obtain experimental data showing the characteristic form of the semi-logarithmic constitutive surfaces on the net total stress and matric suction planes. Two soils, a uniform silt and a glacial till were tested. Specimens were formed by static compaction at half standard Proctor compaction effort with either dry of optimum or at optimum initial water contents. The investigation included specimens being loaded and unloaded under Ko and isotropic conditions. The results were analyzed and used to evaluate the relationships between the moduli. The knowledge of four moduli is needed to completely describe the volume change behaviour of an unsaturated soil in a monotonic volume change process. Special tests are required to determine these four moduli in the laboratory. For instance, the one-dimensional or isotropic compression test, the suction and unconfined shrinkage tests are necessary for solving settlement problems. The use of an approximate semi-logarithmic constitutive surface as a means to relate moduli for the same phase appears to be viable only for the soil structure. The geometry of the approximate soil structure constitutive surfaces is identifiable by two characteristic stress states namely the corrected swelling pressure (i.e., Pś) and the initial stress state translated to the matric suction plane e following a constant volume stress path (i.e., (ua - uw)e/i). Relationships between soil structure moduli can be written e in terms of log (Pś) and log(ua - uw)e/i. The experimental data has revealed empirical relationships between moduli for the water phase. As a whole, six relationships for the eight moduli associated with monotonic volume decrease and increase are suggested. The compressive and swelling indices with respect to the net total stress (i.e., Ct and Cts respectively) can be measured using conventional oedometer or triaxial equipment. These two are regarded as "basic" moduli. The remaining moduli can be estimated from the proposed relationships with the knowledge of the basic moduli and the characteristic stress states, Pś and (ua - uw)e/i.

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published_or_final_version / abstract / toc / Zoology / Master / Master of Philosophy

published_or_final_version / Civil and Structural Engineering / Master / Master of Philosophy

published_or_final_version / Civil and Structural Engineering / Master / Master of Philosophy

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