Variations in some soil physico-chemical properties - a case study for reclassification of soils developed over tarkwaian rocks in the high rainfall forest and the moist semi-deciduous forest zones of Ghana

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1998-02-15
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Abstract
Morphological and chemical properties of soil series developed on the Tarkwaian rocks within the High Rainfall Forest Zone (HRF) and the Moist Semi-Deciduous Forest (MSDF) Zone of Ghana were studied. The main objective was to critically examine the differences in the soils developed over the Tarkwaian rocks in the two ecological zones and to find out if these differences justify reclassification of the soils. Four (4) sites in each of the HRF and MSDF Zones were selected for the study. The soils were identified in the field at the series level along the catena using auger borings and mini pits up to 120 or 150cm or to the parent rock as well as road cuttings encountered in the two areas. Soil characteristics such as soil depth, colour, drainage, texture, structure, and various types of concretions, surface gravelliness and other physical parameters were examined. Nineteen (19) soil profile pits were dug and hundred and thirty (130) soil samples were collected from the profiles in the HRF Zone. In the MSDF Zone, sixteen (16) soil profiles were dug and one hundred and five (105) soil samples were collected. The studies revealed that the physico-chemical properties of the two groups of soils differ from each other. The differences are attributed principally to differences in the climatic conditions prevailing in the two zones. The soils of the HRF Zone which receive nearly 2000mm annual rainfall were found to be deeply weathered and strongly leached than those of the MSDF Zone which receives about 1500 mm of annual rainfall, it was also found that clay bulges were conspicuously absent in the soils of the HRF Zone but glaringly present in the upland sub-soils of the MSDF Zone. Using the FAO/UNESCO and the USDA Classification Systems the soils found in the two ecological zones have been classified. Matured soils in the HRF Zone are mainly Ferralsols by the FAD/UNESCO System (1990) or Oxisols by the USDA System (1998) while those in the MSDF Zone are mainly Alfisols and Ultisols by the FAO/UNESCO System, (1990) or Oxisols by the USDA System (1998).
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A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirement for the award of the Degree of Master of Philosophy in Soil Science (Pedology), 1998
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