Studies analyzing the variability of clay minerals and magnetic susceptibility provide data for the delineation of site-specific management areas since many of their attributes are important to agronomy and the environment. This study aimed to evaluate the spatial variability of clay minerals, magnetic susceptibility, adsorbed phosphorus and physical attributes in Oxisols of sandstones in different geomorphic surfaces. For that purpose, soil samples were collected every 25 m along a transect located within the area where the geomorphic surfaces were identified and mapped. The transect occupied the central portion of 500 ha, where it was also sampled for density purposes with one sample per six hectares. Soil samples were collected at a depth

One of the marks left by prehistoric man in the Amazonas landscape are the dark-colored soil stains, Archeological Dark Earth (ADE), which are rich in organic matter, phosphorus and calcium. The color in this soil is presented as an attribute of difficult interpretation on the horizon, and the studies towards a better identification are important. In this sense, the objective of this study was to characterize the color and iron oxides of the ADE clay fraction in Apuí region in southern Amazonas. Six trenches were opened, where these profiles were characterized morphologically, and also samples were collected per horizon for later performance of grain size analysis, flocculation, water clay dispersion and chemicals (pH in water and potassium chloride, calcium, magnesium, potassium, phosphorus, potential acidity, f, organic carbon and organic matter) and mineralogical analyses. The data were submitted to principal component analysis. Similar behavior in the studied profiles was found both in physical and chemical attributes. It was concluded that the hematite and goethite, determined by x-ray diffraction and diffuse reflectance spectroscopy, besides not presenting significant variations between the studied soils, present similar characteristics to non-anthropogenic Brazilian soils. The color measured by diffuse reflectance spectroscopy proved efficient to indicate variations among the ADEs, proving to be an innovative technique, efficient and promising for indirect quantification of soil characteristics in a simple and low cost manner. The results show that iron oxides demonstrate be sensitive indicators of pedoenvironmental conditions and pedogenic processes of Archeological Dark Earth.

No abstract

No abstract