Dissertations and Theses

Summary

This study aimed to evaluate the utilization of magnetic susceptibility and diffuse reflectance spectroscopy to identify areas with different soil support capacity for application of vinasse and with different potential for adsorption of phosphorus for sugarcane. For determination of the chemical, of clay content, measuring the magnetic susceptibility and the diffuse reflectance spectroscopy, 86 soil samples were collected, every 30 meters on a transect of 2600 meters, following the crest of landscape along the sugarcane crop area, in order to obtain points in the different soil classes, and more 155 points were collected, into a grid of sample density of 1 point per 2.5 ha, totaling 241 points in the experimental area of 380 ha. From the soil color data (hue, value and chroma) was calculated a redness index, and the calculations of levels and soil support capacity for application of vinasse, and phosphorus adsorbed to each experimental grid point were also performed. Regression models were built between the magnetic susceptibility and other studied attributes, and between redness index and adsorbed phosphorus. Data were analyzed using descriptive statistics, and the attributes average values were also calculated for each soil class of the experimental area and the Tukey test at 5 % was applied. The spatial dependence analysis of data was performed using geostatistics by the variograms. Spatial pattern maps and cross variograms were also constructed. The results indicate that the magnetic susceptibility has the potential to assist in identifying areas with different soil support capacity for application of vinasse and with different phosphorus adsorption potential. The magnetic susceptibility shows spatial and linear correlation with vinasse levels, with soil support capacity for application of vinasse, and with the adsorbed phosphorus, so it can be used as pedotransfer function for the indirect quantification of these attributes. The redness index shows no linear correlation with adsorbed phosphorus, but has spatial correlation with it. This demonstrates the soil color potential to assist in mapping phosphorus adsorption areas and the importance of using geostatistical techniques for soil properties variability studies. The formula for calculating vinasse levels proposed by CETESB is effective, but the suggested sampling density cannot capture changes that occur in the field, which can result in the wrong levels recommendation of vinasse as the soil support capacity. The recommended levels of vinasse through spatial patterns maps and through soil classes showed greater rationalization in the application of this effluent than when compared with the recommendation of CETESB, decreasing possible risks of environmental impacts and taking advantage of the best fertilizing potential of vinasse.