Using proximal sensors to assess pedogenetic development of Inceptisols and Oxisols in Brazil

Abstract

Proximal sensors like portable the X-ray fluorescence (pXRF) spectrometer, visible and near-infrared spectrometer (Vis-NIR) and magnetic susceptibilimeter have been increasingly used for the acquisition of complementary data to investigate chemical, physical and mineralogical properties of soils. Through the association between these sensors, this study aims to differentiate classes of soils with similar pedogenetic development, but developed from different parent materials. Four soil profiles were described and sampled in Lavras, Minas Gerais, Brazil: Oxic Dystrustept and Anionic Acrudox, developed from gabbro and Typic Dystrustept and Rhodic Hapludox, developed from gneiss. Samples from the A, B and C horizons were subjected to analyses by pXRF, Vis-NIR, and magnetic susceptibility, in additon to their physicochemical characterization and determination of their mineralogy via X-ray diffraction (XRD). The contents of Si, Fe and Ti obtained by pXRF as well as the MS values were decisive in distinguishing soil classes according to the parent material. The spectral curves generated by Vis-NIR showed different spectral responses for the same soil class due to their differential mineralogical constitution. Soils developed from gabbro had higher contents of iron oxides and a low reflectance in relation to the soils developed from gneiss. The proximal sensors contributed to the differentialtion of soil properties both within soils developed from the same parent material, mainly expressing their different weathering degrees, and within soils of the same taxonomic order, but developed from distinct parent materials. These proximal sensors can improve the characterization of soils and evaluations about their genesis at reduced time and costs.