Atributos químicos, físico-hídricos e mineralogia da fração argila em solos do Baixo Amazonas: Serra de Parintins

Abstract

The latest studies of attributes of soil of the Amazonian ecosystems provide information to make up a survey on these soil conditions in the face of several forms of changes they are submitted. This work aimed to describe and evaluate physical and hydric evolution as well oxisol mineralogy in lower Amazon in order to comprehend variations of these attributes in different vegetative covers. Deformed and non-deformed samples were collected for physical, chemical, hydric and mineralogical analyses, respectively in two points of a topographic sequence in Serra de Parintins: plateau and watershed, being showed three profiles of soil in each position. The results showed that predominant forest of the plateau and watershed profiles provide proper physical and hydric conditions for a good aggregation, higher intensity of large pores, larger saturated hydraulic conductivity (Ko) and better hydric retention of soils. Similar fact occurs in secondary forest, presenting such areas good permeability, porosity and water retention in soil. Carbon accumulation is higher in watershed profiles, decreasing in depth and relating directly with Ko and root system. Mineralogical analysis of clay fraction points kaolinite as predominant followed by gypsum, goethita, quartzo and anatásio, showing no variations along landscape. Serra de Parintins has poor acid clay soil of medium texture accumulating plintita on subsurface horizons, avoiding the phenomenon of terras caídas. A high gradient of volumetric humidity is observed on subsurface horizons, showing water retention when compared to surface horizons.