Dissertations and Theses

Summary

The objective of this study was to evaluate the potential of diffuse reflectance spectroscopy (DRE) to aid the characterization of CO2 emission and soil attributes. The study was carried out in an irregular mesh of 50 m x 50 m, containing 89 points, with a minimum spacing of 0.50 m and a maximum of 10 m between points, in the 0.00 - 0.10 m depth layer. Linear correlations of the hematite (Hm) and goethite (Gt) minerals, determined by the ERD, with the CO2 emission of the soil (FCO2) and other attributes were performed. The anisotropic characterization of the variables was performed for the 0 °, 45 °, 90 ° and 135 ° directions in relation to the planting line (0 °). The results indicate that ERD is an efficient method in the identification and indirect quantification of Hm and Gt. The values of soil respiration measured in the field were correlated with the values of Hm (R2 = 0.41), Gt (R2 = 0.42) and iron dithionite (Fed) (R2 = 0.34). The water free porosity (PLA) was also correlated with the contents of Hm (R2 = 0.41), Gt (R2 = 0.39) and Fed (R2 = 0.46). The analysis of geostatistics indicated the existence of anisotropy of all studied variables, including the mineralogical attributes, indicating a degree of moderate to strong spatial dependence for almost all attributes of the soil. The variables that best explained the anisotropic variations of soil CO2 emission were PLA (58%), soil moisture (54%), Hm (13%), Fed (8%) and soil temperature (7%). These results prove that this innovative technique is an attractive alternative to support the indirect quantification of soil attributes and the FCO2 survey, showing its potential to replace a large part of the conventional laboratory analyzes. In addition, this methodology assists in the rapid verification of the anisotropic behavior of FCO2 and other soil attributes, and can be used to make feasible mapping of emissions in large areas, integrating studies of greenhouse gas inventories in agricultural soils.