Terrain attributes and spatial distribution of soil mineralogical attributes

Abstract In soil studies, there is an increasing tendency to quantify heterogeneous soil attributes by georeferencing, leading to the pedometry. In this context, terrain attributes play important role for the characterization of distinct surfaces under different pedogenetic processes. The soil mineralogical assembly expresses factors and pedogenetic processes involved in soil formation that affect their physical and chemical characteristics. This work objective was to investigate the spatial distribution of soil mineralogical attributes, using topographic terrain attributes as tools for the characterization of high or low mineral content environments and their relationships with soil chemical characteristics. This study was carried out in the Cangüiri Experiment Station of the Federal University of Paraná, at Curitiba, State of Paraná, Brazil. Soil sampling in the studied area was collected in a regular grid of 135 points. The clay fraction, after dithionite–citrate–bicarbonate (DCB) extraction, was analyzed to determine kaolinite (Ka) and gibbsite (Gb) concentrations by thermogravimetry (TG) and their respective dehydroxylation temperature peaks. Such mineral crystallographic attributes were determined by X-ray diffraction (XRD). High amorphous Al contents tended to be related to higher organic carbon (OC) values, in which areas the terrain attributes indicated smooth relief and predominance of pedimentation processes. The terrain attributes differentiated areas with higher Ka/(Ka + Gb) ratios, that is, with higher Ka values, located near drainage channels and with silica accumulation, meanwhile areas with higher proportion of Gb were found on flat summit. The mineralogical attributes studied in this work influenced some soil chemical characteristics. Satisfactory results were obtained with the use of topographic terrain attributes to characterize distinct surfaces, since they were related to some of the mineralogical attributes formation.