Formas extraíveis de ferro em solos do estado do Rio de Janeiro

The state of Rio de Janeiro, Brazil, is characterized by three main geomorphologic formations, the landform constituted by crystalline rocks, exposed or covered by their alteration products; coastal tablelands, formed by Barreiras Formation Tertiary sediments; and alluvial floodplain sediments of Quaternary age. Differences between parent material and topography and their influence on soil genesis have been the main subject of studies in Rio de Janeiro. The objective of this study was to analyze the behavior of extractable forms of iron, Feo, Fed and Fes, and their respective ratios as related to the pedogenesis degree of Rio de Janeiro soils. The iron forms and Fed/Fes and Feo/Fed ratios expressed variations in the mineralogical nature of the parent material, degree of weathering of the soils and parent material, or drainage class, more than pedogenesis intensity. The use of the extractable forms of iron and respective ratios to measure pedogenesis degree in the soils of Rio de Janeiro State requires an association with other soil properties, especially morphology and drainage class.