Development of the structure of podzolics and latosols derivate from granulite in humid zone

Abstract

In order to determine the facture that influence the formation of the structure of the B horizon of Podzolics and Latosols, four profiles were studied. These profiles are located in the Cacao Zone of Bahia. The climate of the area is the Af of Köppen. Based in the morphological, physical, chemical, mineralogical and micromorphological data of profiles, new mineralogical studies of the fraction <2 µ were developed. In these studies were use X-ray diffractometer and electron microscope, interpretation of results of free iron (Tamm) and total iron (HCI), as well as analyses of curves obtained through the method of Kinetic extraction, aiming the identification of possible amorphous of iron and alumina. As regards the mineralogy of the fraction <2 µ, it was verified a relation between the predominance of halloysite (7Å) and structure moderate very fine angular and subangular blocky; it was also verified that the predominance of kaolinite with or without disorder in the b axis and/or gibbsite was related to ultra fine granular structure, called "coffee powder". No relation was found between floculation degree and structure. The clays are very flocculated in all horizons (GF 90 to 100%).