Study of the physical, chemical and mineralogical characteristics of some vertisols of Ethiopia
2001
Eylachew Zewdie (EARO, Addis Abeba (Ethiopia))
A study was conducted on vertisol profiles develped at different locations (Wonji, Ginchi, sheno and Alemaya) to know their differences and similarities in physicochemical and mineralogical properties. After survey works in each location, profiles were opened and described using USDA Soil Survey Manual (1981). Samples were collected from each pedologically identified horizon and analysed for different physical, chemical and mineralogical properties using the standard analytical methods. The clay fraction (2 miwu meter) was studied by the use of x-ray diffractometery. The results confirmed that in Ethiopia, Vertisols do not show bit difference in their properties and manifest massive upwards movement of parallelepiped structural aggregates (angular and subangular blocky) with strong slickensides. These structural aggregate have distinct cleavage planes with 45 degree orientation. At Ginichi micro-relief is common compared to the rest. Except subsurfact horizons of vertisols at Wonji, which have fluvice origin, the rest have high clay conten (50%). The bulk density increases downward in all profiles (1.08-1.94 g/cc). In general, all have alkaline reactions. Smectite (14-94%) and illite (2041%) dominate both surface and subsurface horizons. Illite was also found to be the only clay mineral of C-horizons and has significant contribution to the stability of physico chemical characteristics of the pedons. Fe and Mn are found to be doninant in all profiles.
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