The salient points of the thesis are summarised as follows: Chapter one: The geographical features including the location of the site, the discussion of subtropical climates, the world pattern of aridity, climatic changes in the tropics, and finally the topography, drainage and the vegetation of the area are reviewed. Chapter two: A general review of the geology, hydrogeology, hydrology, and geomorphology IS of the area ~~ covered. The geomorphic history of the area and its relation // to land formation, and the origin and development of domed and boulder inselbergs are generally discussed. A brief classification and illustrations of the geomorphic units in Kordofan provinces are given. Chapter three: In this chapter a review of the literature concerning the soils of arid and semi-arid regions is presented. The factors of soil formation, especially the climate, topography and parent material, are given.- The soil fo~ming.processes, in particular the weathering and formation of deep profiles are discussed. Accumulation of organic matter in the tropics and ~ the development of horizons such as gypsic, calcic, ~atric, salic, argillic and sesquioxides are reviewed. r,hap~er four: In this chapter a review of the work carried out in Western Sudan and the relationship of soils to the geomorphology is given. A brief account of soil conservation and m~nagement is also considered especially concerning water movement, erosion, and evapc~ranspiration. Chapter five: The detailed soil survey of the clayey pediplain soils carried out in 1973 is described together with their chemical and physical properties. - GL~l Some results on the water movement through the soils~also included. The soils generally showed neutral to alkaline reaction in their property with increasing alkalinity with depth. The soluble salts at the surface are mainly of calcium, sodium and magnesiUm. In the lower horizons the sodiumcalcium and magnesium chlorides and sulphates are dominant. The water movement through the soil is rapid when the soil is dry decreasing to very slow when wet. This might perhaps be due to the increase in the concentration of salts of sodium when reacting with water causing dispersion. Chapter six: While carrying out the laboratory investigations given in chapter six certain discrepancies in the results became obvious; in particular, particle size analysis, cations excahangeable capacity and exchangeable cations. Therefore some experiments were performed to determine the best me'thod for such soils. For the particle size analysis the pipette method gave high results for the clay fraction, so did wet sieving followed by the hydrometer method. The Bouyocos (1927) method gave very low values for the clay. Chapter seven: A detailed pedological characterisation of selected "Gardud" soils is described. Profiles 1, 2, 3 on the slope show similar morphological features, the coiour is yellowish red at the surface changing slightly to dark yellowi~h brown then to dark brown in the lower horizons. The lower profile No. (4) in the depression is dark yellowish brown in colour. The texture is uniform sandy clay loam in soils on the slope changing to sandy clay in the depressions. The chemical analyses are similar to those that have been described in chapter four, except that the C.E.C. is mod~rately high ranging between 15 and 30 meq/100 g soil. The organic matter and CIN ratios are lower and the soil reaction is neutral to alkaline. In the later work carried out in 1976 there is a slight increase in Clay in almost all the profiles and also a lesser amount of soluble salts which may be due to the sheet erosion, both the clay and soluble salts being washed horizontally by seasonal water. Chapter eight: The detailed results of the micromorphological and mineralogical properties are given. All the soils except the Vertisol (profile No 4) have similar properties, viz. compact.alveolar structure with strong anisotropic soil matrix and abundant domains and aureoles. The subangular and subrounded quartz grains indicate that they are pedisediments. Although some well rounded quartz grains indic~te that there is some wind blown sand.This strong anisotropic soil matrix might be the reason for soil hardness and the alveolar structure. A few whole soil coatings occur indicating that tne soil has undergone several cycles of expansion and contraction. Profile No. (4) has a massive to wedge structure with many calcite carbonate concretions, and some gypsum crystals occur observed at depth. The mineralogical studies confirmed that the soils are highly weathered and have been derived from metamorphic and igneous parent materials. The quartz dominates the light minerals followed by a little biotite, calcite, feldspar and sometimes muscovite. The heavy minerals were dominated by the opaques followed by a little rutile, zircon, kyanite, tourmaline and others. The scanning electron microscope results showed clearly tha~ the soil matrix is well organized overlapping clay sheets and that the quartz grains are well embedded in it. Chapter nine: A discussion of the results· and final conclusions are given. Finally there are four appendices containing results
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:470105 |
| Date | January 1978 |
| Creators | Razig, Mohamed Gaily Abdel |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=185975 |
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