Gênese de cambissolos desenvolvidos de rocha calcária na Chapada do Apodi - CE

Abstract

The Apodi Plateau, located in the semi arid region of Brazil, is caracterized by, eutrophic soils calcareous and flat terrain large agricultural enterprises in the region. However, studies that address the genesis of these soils are required, in order to explain the variation of soil types found in the region. It is hypothesized that the surface microrelief associated with subsurface relief, determine the movement of water in the soil, resulting in different environments pedogenic. The aim of this study was to evaluate the influence of the microrelief surface and subsurface on the genesis from soils in the Apodi Plateau. An area of 102 ha was studied soil profile were colected and analised microrelief features (concave, convex and plain). All soil samples were analised chemical analysis, particle size and mineralogy. Undisturbed soil samples were collected from the diagnostic horizons for micromorphological analysis. Based on chemical data, soils were characterized by high base saturation, (eutrophic) and near neutral to alkaline reaction. The morphological description and radargrams indicate that the soil located on the concave surface are thicker, probably as a result of a high intensity of water soil formation. The soil oxides, the Ki ratio indicates the presence of soil more weathered on the concave surface. Micromorphological descriptions indicate soils with lower pedalidade in the convex surface Features of calcium carbonate precipitations were not identified in the concave surface, however, precipitation of calcite was identified in soil plain,surface, thus indicating a different environments pedogenesis. The ratio G / F indicates a lower contents of coarse particles in profiles 4 and 5. The XRD showed the presence of expandable clayminerlas’s in convex and plain terrain, and the dominance of kaolinite in the concave surface. As to iron oxides, it is noted that the environment favors goethite in however with a co-dominance hematite.