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Title: Phosphorus Adsorption Isotherms of Some Selected Soils from the Eastern Region of Ghana
Authors: Amarh, Flora
Issue Date: 19-Oct-2012
Abstract: Phosphorus (P) sorption in soils is a key process governing its availability to crops and environmental consequences. As a result of the high P fixation (low soil solution P concentration) in soils worldwide, crop yields are often low. In view of this fact, this study was initiated to determine the P sorption characteristics of some soils and derive parameter estimates relevant in the prediction and management of P as well as their relationship to the properties of the soils. Twelve soil samples were obtained from the Eastern Region of Ghana for this study. Measurement of P sorption was conducted by equilibrating air dried soil (<2 mm) in 0.2 M CaCl2 solution containing various concentrations of P. Phosphorus concentrations in the equilibrium solution were determined by the molybdenum blue method. The amount of P sorbed by the soils differed among the various soils. Differences in P- adsorption were greatly influenced by soil properties like soil organic carbon (SOC), soil pH, amounts of calcium and aluminium and the clay content. Soil from Huhunya which was virgin, adsorbed the greatest P, and the least P was also adsorbed by soil from a plantain farm in Huhunya. Phosphorus sorption data for soils was fitted to the Langmuir, Freundlich and Temkin isotherm equations. Phosphate adsorption was well described by the three isotherm equations but the Langmuir adsorption isotherm provided the best fit to the experimental data. The three parameters derived from the Langmuir isotherm are the adsorption maximum (Kmax), bonding capacity (b) and the maximum buffering capacity. Adsorption maximum and bonding capacities estimated ranged from 109.89 μg/g to 625.00 μg/g with an average value of 211.61 μg/g and from 0.124 mL/μg to 0.692 mL/μg with an average value of 0.285 mL/μg respectively. Maximum buffering capacity also ranged from 19.235 to 294.125 with an average value of 72.55. The sorption capacity (a) and sorption energy (n) were v estimated from the Freundlich equation and they ranged from 37.601 to 224.388 μg/g and 2.721 to 5.988 with average values of 82.965 μg/g and 3.930 respectively. Buffering capacity (B) which was estimated from the Temkin equation ranged from 16.915 to 103.350, with an average value of 37.991. It was realized that virgin soil from Huhunya would require the most P fertilizer. The least P fertilizer would be required by soil from the plantain farm (HP). Correlation analysis showed significant relationship between some soil characteristics and the sorption parameters derived from the three equations. There is however the need for inclusion of more soil chemical, physical and mineralogical properties in predicting soil P-adsorption to enhance reliability of information.
Description: A thesis submitted to the Department of Chemistry, Kwame Nkrumah University of Science and Technology in partial fulfilment of the requirements for the degree of Master of Science in Analytical Chemistry, October-2012
URI: http://hdl.handle.net/123456789/5804
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