Dissertations and Theses

Summary

Sugar cane currently appears in the Brazilian agricultural scene as one of the main crops, presenting a great expansion not only in the State of São Paulo, but also in several other Brazilian states. Due to this expansion and to the federal laws that regulate the end of the burning of the cane fields, the sugarcane harvest has been passing through a transition period, no longer being carried out manually and with the burning of sugarcane. to be harvested with machine and without burning (raw cane). With the change in the form of harvest a great amount of straw has been left on the ground, creating in the pedoambiente conditions that can cause changes in the chemical, physical properties and even in iron oxides, that are considered attributes of the soil stable for long time . Thus, the present work aimed to characterize the variations of the chemical, physical and mineralogical attributes of the soil submitted to two different types of sugarcane harvest and determine the spatial variability of these soil attributes in areas of raw cane harvest and burned cane. Two plots of approximately one hectare each were delimited in areas with raw cane and burnt reed. Soil samples were collected in each area at 126 points, at depths of 0.0-0.25 and 0.25-0.50 m. The samples were submitted to chemical, physical and mineralogical analyzes. At the depth of 0.0-0.25 m, 20 points were chosen in each area, which were submitted to the analysis of the degree of humification of the organic matter of the soil. The results of the analyzes were submitted to the analysis of descriptive statistics with test of comparison of means, to the multivariate statistical analysis of groupings and also to the analysis of main components. Subsequently, geostatistical analyzes were performed, obtaining spatial dependence, semivariograms and kriging maps of the attributes studied. To analyze the spatial correlation between the attributes studied, cross-linked semivariograms were constructed. The addition of organic material to the soil provided an improvement in the physical attributes of the soil and the quality of the organic matter, while the area of cane burned presented better soil fertility than the raw cane system at both depths evaluated. The application of multivariate statistics allowed the division of all attributes studied in two different management groups (raw cane and burned cane). The raw cane harvesting system promoted pedoenvironmental conditions that caused alterations in the crystallography of iron oxides, an increase in the degree of humification and a lower adsorption of phosphorus in this area in relation to the burned sugar cane system. The spatial variability of the chemical attributes is higher in areas with raw cane harvest when compared to areas of cane harvesting.