Dissertations and Theses

RELATIONS BETWEEN CLAY MINERALOGY, MAGNETIC SUSCEPTIBILITY AND PHOSPHORUS ADSORPTION IN OXISOLS IN THE REGION OF JABOTICABAL, SP

Author: Livia Arantes Camargo

Keywords: diffuse reflectance spectroscopy, gibbsite, iron oxides, kaolinite, pedotransfer function, spatial variability

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Summary

This study aims to characterize the clay mineralogy and magnetic susceptibility in different geomorphic surfaces, evaluate the correlation between x-ray diffraction and diffuse reflectance spectroscopy in the estimation of goethite and hematite, the influence of iron oxides on the adsorption phosphorus as well as the calibration and validation of pedotransfer functions for predicting adsorbed phosphorus using iron oxides and magnetic susceptibility. An area of 500 hectares was delineated and a soil sample every six hectares was collected in depth from 0.0 to 0.20 m. A transect was leased, and soil samples were collected every 25 meters. In each geomorphic surface mapped in the area were collected approximately 20 soil samples arranged on either side of the transect. Soil samples were taken to the laboratory for carrying out particle size analysis, physical, mineralogical, adsorbed phosphorus and magnetic susceptibility. The goethite and hematite were estimated using the ratio of iron oxides obtained by x-ray diffraction and by diffuse reflectance spectroscopy. The results of the analysis were subjected to statistical analysis and geostatistical, and pedotransfer functions were calibrated and validated to predict the adsorbed phosphorus and its mapping. The results showed that: The spatial variability of crystallinity and of the content of the iron oxides, as well as the magnetic susceptibility is dependent on the age of the geomorphic surfaces. The surface newest (III) has a higher spatial variability of these attributes. The clay minerals influence the soil physical properties. The characterization of the spatial variability of iron oxides and magnetic susceptibility allows the delineation of homogeneous areas that may be relevant future ace soil series and the specific management areas. The goethite and hematite estimated by diffuse reflectance spectroscopy are related to those estimated by x-ray diffraction. The geomorphic surfaces influencing variability of goethite and hematite, and consequently the variability of phosphorus adsorbed. The magnetic susceptibility among the attributes studied, is the predictor variable of a pedotransfer function that enables the mapping of phosphorus adsorbed with greater accuracy.