No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

aThis study was undertaken to investigate the possibility of substituting the currently used and more expensive superphosphate (TSP) by rock phosphate (RP) as a phosphatic fertilizer for tea cultivation. Five top soil samples and four corresponding subsoils were selected from the tea-growing areas of Bangladesh. These soils were extremely acid and poor in nutrient status, with moderate to high P adsorption capacities. Phosphatic fertilizer dissolution and incubation studies showed that RP is about 70% and 50% effective, respectively, in releasing exchangeable P as RP. Incubation of a Scottish sub-soil showed that RP was 40% as effective in releasing exchangeable calcium. Two series of glasshouse trials were designed to run consecutively, using rye (Secale cereale) as test crop. Phosphate was applied as Gafsa RP and TSP at rates of 0, 50, 100, 200 and 300 mg P kg⁻¹ with N and K as a basal dressing in the first experiment; N and Mg were applied in the second, with no further P application. In the first experiment, TSP gave higher total dry matter yield and P uptake than RP, whereas in the second experiment RP gave decidedly higher yield and uptake than TSP. The efficiency of RP relative to TSP in increasing total P uptake at corresponding levels of application ranged from 60% to 108%, increasing to 80% to 130% in the second experiment. In both experiments, the RP treatments increased the pH and exchangeable calcium content of the soil more than TSP, whereas resin-extractable P was higher after TSP treatments. The results lend encouragement to the extension of this work to field trials with tea, in the expectation that RP will not only increase yields but, through its residual value, increase soil fertility, providing considerable commercial and economic benefit.

The main aims of this thesis are to present data concerning the morphology and evolution of this previously neglected coastline and to develop a tentative chronological model of its evolution during the Late Tertiary and Quaternary. To achieve the first aim, analysis of topographic and geological maps, as well as aerial photographs was carried out in addition to field mapping. The second aim was achieved by analyzing the raised shore platforms and associated deposits in terms of (1) their altitude using appropriate techniques, (2) radiocarbon dating of shell and coral fragments and (3) some sedimentary analysis. The altitudinal measurements allowed the construction of a height-distance diagram. Five samples of shell and coral fragments from raised beaches and coral terrace ranging in heights from 3m to 14m above sea level yielded dates that range from 26,400 ± 550 to > 40,000 year BP. Based on the data collected and observations made, a tentative chronological model of the evolution of the present coastline, and of the formation and development of the raised shore platforms during the Late Tertiary and Quaternary is presented. This model views the evolution of the present study coast as being affected not only by marine action associated with eustatic sea level changes since Late Tertiary times but also by tectonic uplift, and to a lesser extent fluvial action and subaerial weathering processes. That there is relatively little correspondence in the altitudes of shorelines across major fault lines which intersect the coastline is taken as evidence of differential tectonic uplift producing horst and graben structures. Possible developmental sequences of differential uplift to produce the altitudinal sequence observed are discussed. The radiocarbon dates indicate that none of the shorelines is Holocene in age but, because of possible contamination by younger carbon, their dates could be figures that represent Quaternary dates underestimated by a considerable margin. The results are discussed in the context of the limited number of other studies of coastal evolution carried out in the surrounding area.

It has been repeatedly maintained that large parts of the rivers and streams of South Wales are not related to the inherent geological structure. This study is concerned with the identification of the jointing pattern in Devonian and Carboniferous strata for a region of the North Crop of the South Wales Coalfield between Ammanford (in the west) and Glynneath (in the east), which includes the complete Amman catchment and the upper reaches of the Tawe and Neath. Once such joint orientations had been recorded by intensive fieldwork, their influence on drainage development and evolution was attempted. Before the fieldwork programme was planned in detail, a pilot study was carried out to investigate the influence of joints on the guidance of stream networks. A positive response to such an investigation suggested that a more detailed study would be worthwhile. The joints at 168 sites were recorded, adopting a sampling design proposed by the author. This data was quantitatively analysed to derive values of preferred orientation for each joint site and to obtain a classification of joint orientations at the individual basin and inter-network levels, and thus examine the spatial variation of the dominant joint trends. The orientations of stream patterns were examined using the O.S. 1:10,560 maps and, once again, the derived data was carefully analysed in a similar fashion to that of the joint information. Comparisons between both types of orientational data during the course of fieldwork and, later, statistical analysis, revealed that large areas of the drainage network exhibited a high degree of structural adaptation. Other elements of the landscape considered were the orientations of valleys and those cave passages that are typical of the Carboniferous Limestone topography of the Tawe, Neath, Mellte, and Hepste river valleys. Once again, when the characteristic features of both these latter forms of orientational data were compared statistically with the joint trends, a high level of association was readily observed. Although this study did not discover any firm evidence that allowed a detailed chronological sequence of drainage development to be proposed, it did provide numerous examples where the geological structure, in the form of joint planes, has played a critical part in the development and subsequent evolution of the fluvial landscape of this sector of the South Wales Coalfield. Thus, while not suggesting the absence of the Chalk initially, its significance in drainage evolution was not thought to be that considerable.