Effect of Soil Properties on Bioavailability of Aluminum and Phosphorus in Selected Kenyan and Brazilian Acid Soils

Effect of Soil Properties on Bioavailability of Aluminum and Phosphorus in Selected Kenyan and Brazilian Acid Soils

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Declining agricultural productivity in many parts of Africa is negatively affecting the livelihood of many people. Information on the fertility status of many of these fragile soils is scarce. To determine the soil factors responsible for the decline in soil productivity in the Kenyan highlands, 11 representative sites were selected, described in the field, and sampled for laboratory analyses. They were compared with selected soils from the Cerrado region of central Brazil where crop production has increased significantly since the 1960s due to improved crop varieties and soil nutrient management strategies. Soils east of the Rift Valley (Mt. Kenya region) were significantly different from those west of the Rift Valley. The topsoils of the pedons east of the Rift Valley had andic properties, were 0.75 pHH2O units more acidic, had 37% higher aluminum (Al) saturation, and about two to three times greater phosphorus sorption capacity (PSC) than the topsoils west of the Rift Valley. The soils from western Kenya were generally comparable to the Brazilian Cerrado soils with the exception that the exchange properties of the Brazilian soils were lower. Overall, Al saturation of both the Kenyan and Brazilian soils varied from 0-69%, and PSC ranged from 426-3333 mg kg-1. The PSCs of the Brazilian topsoils were, however, not significantly different from the western Kenya soils. Both the Kenyan and Brazilian soils were generally high in dithionate-citratebicarbonate and ammonium oxalate extractable iron (Fe) and Al. X-ray diffraction, electron microscopy and thermal gravimetric analyses indicated that the clay fractions of both the Kenyan and Brazilian soils were dominated by kaolinite. In addition, spheroidal and rolled-up sheets of halloysite were also identified in the Kenyan soil clays. Among the Kenyan soils, gibbsite was relatively abundant in the volcanic ash derived soils east the Rift Valley, while soils west of the Rift Valley contained appreciable amounts of 2:1 phyllosilicates inherited from the parent rocks. Most of the Brazilian soils contained significant amounts of gibbsite, and in some cases, minor amounts of 2:1 phyllosilicates. In light of these findings, the western Kenya soils are likely to respond to nutrient management practices that are similar to those used in central Brazil, while the soils from the Mt. Kenya region will require crop varieties and management strategies tailored to higher Al toxicity and phosphorus sorptive capacity.MPhil Thesis, Moi University, Kenya. Ohki, K. 1987. Aluminum stress on sorghum growth and nutrient relationships, Plant Soil. 98:195-202. Okalebo, J. R., Gathua, K. W. and Woomer, P. L. 1993. Laboratory methods of soil and plant Analysis.


Title:Effect of Soil Properties on Bioavailability of Aluminum and Phosphorus in Selected Kenyan and Brazilian Acid Soils
Author: Pamela Achieng Obura
Publisher:ProQuest - 2008
ISBN-13:

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