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" Biogeochemistry of phosphorus in the highland plateau soils of Ethiopia "
M. D. Garoma
W. P. S. Robarge, Thomas J.
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Latin Dissertation
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| Language of Document
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English
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| Record Number
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1113047
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| Doc. No
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TLpq304267401
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| Main Entry
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M. D. Garoma
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W. P. S. Robarge, Thomas J.
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| Title & Author
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Biogeochemistry of phosphorus in the highland plateau soils of Ethiopia\ M. D. GaromaW. P. S. Robarge, Thomas J.
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| College
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North Carolina State University
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| Date
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1996
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| student score
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1996
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| Degree
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Ph.D.
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| Page No
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128
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| Abstract
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Surface horizon samples from two Vertisols, an Andisol, and an Alfisol were collected from farmers' fields, research station farms, and uncultivated/non-fertilized areas to characterize the organic and inorganic forms of P, to describe the equilibrium P sorption-desorption characteristics, and to investigate possible mechanisms of P retention. Soil samples collected from farmer's fields showed a decrease in the labile P (resin Pi, bicarbonate Pi and Po) fractions as compared to the uncultivated/non-fertilized sites. However, under research station management, the labile P fraction was observed to increase or was maintained at the same level as the uncultivated/non-fertilized soil samples. A decrease in the labile P fraction in the samples collected from farmer's fields resulted in an increase in the amount of P sorbed mainly due to the presence of unoccupied P retention sites as compared to the uncultivated and research station soil samples. Resin extractable P accounted for 81% of the variability in P sorption capacity of the soil samples. This suggests that resin extractable P provides an excellent estimate of P sorbed to sites that react rapidly with P addition. Increasing ionic strength in this study always increased P retention. Very little difference in P retention was observed between CaCl2 and KCI for both Vertisols at all pH levels which suggests that Ca was not bound in the Stem layer. However, for the surface soil samples with constant potential surfaces (Andisols), sorption of P was highest in CaCl2 which could be due to the ability of the cation to enter the Stem layer and further reduce the negative potential in the plane of sorption. This study suggests that the P status of the highland plateau soils of Ethiopia under farmer's management may be nearing exhaustion as compared to the uncultivated or research station soils. Therefore, P calibration studies conducted on research station farms, destined for farmers utilization, may not reflect the local farmers condition.
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Biogeochemistry
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Biological sciences
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Earth sciences
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Health and environmental sciences
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ionic strength
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sorption
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