Characterization, classification and clay mineralogy of soils along toposequence at Cheha Woreda, Gurage zone, Ethiopia

Abstract

Abstract Because soil is a natural material, it differs greatly from place to place and is not consistent throughout the terrain. It varies in their properties, changing across the landscape and vertically down the soil profile. The objective of the study was to characterize, classify, and study the clay mineralogy of the soils along the toposequence. Field survey and soil laboratory analysis were carried out to characterize selected morphological, and physicochemical characteristics and study clay mineralogy of the soil in the study area. The clay mineral was identified using X-ray diffraction. The surface soils were generally very dark brown (7.5YR 3/3) to black (5Y 2.5/1) in color when moist; deep (100-150) to very deep (>150 cm) in depth and clay content varying from 40 to 80 % throughout the profiles in the peons. The consistence of the surface soil was very friable to friable when moist and sticky plastic when wet; moderate bulk density (1.35 to 1.57 gm/cm3). The soils were moderately acidic to slightly neutral with pH values between 5.48 and 7.8. The ratings of organic carbon and total nitrogen contents were medium on the surface and low in subsurface horizons. The CEC of the soils, both the surface and subsurface of the three upper pedons, were rated as high. Available phosphorus content of the soils in the surface and subsurface horizons of all the pedons were very low. Kaolinite, hematite, illite and quartz were found in the three upper pedons whereas montmorillonite was dominantly existed in the toe pedon. Based on the field description and soil analytical results, two main reference soil groups namely, Luvisols and Vertisols were obtained along the topographic position. It is concluded that topography at the study site affected the features of the soils, which resulted in significant variations in soil properties throughout the toposequence.