Tese
Mineralogia da fração argila de um argissolo submetido ao sistema de plantio direto por vinte e quatro anos
Fecha
2018-03-27Autor
Lorensi, Juliana
Institución
Resumen
In the last decades, it has been more intensive the development and improvement of
techniques which aim to provide the sustainability of productive farming systems, while
increasing their yields. In this scenario, is included the no-tillage system (SPD), which
continuous use, observing the practices recommended by the management system besides the
soil preservation practices, has been showed noticeable effects on the improvement of soil
physical, biological and, possibly, mineralogical attributes. The main goal of this work was to
evaluate the no-tillage system effects on the soil Fe oxides and kaolinite (Kt), resulted from 24
years using the following management systems: i) absence of agricultural cultivation, ii) SPD
without grazing, iii) SPD with grazing simulation and iiv) native pasture – control. The effects
evaluation was made through a chemical attributes analysis, use of x-ray diffraction and thermal
analysis techniques, applied on soil layers of 0-5cm and 5-10cm in a Typic Paleudalf of the
Central Depression region of Rio Grande do Sul. Although some physical and chemical
attributes were altered, through the techniques used it was not possible to show treatments
effects on Fe oxides, Kt and 2: 1 amounts mineralogy changes after 24 years of implantation
on the Paleudalf. The Fe oxides abundance indicated the predominance of crystalline forms
over the low crystallinity ones in all treatments and in the control, which did not have
differences between the two layers. The isomorphic substitutions of Fe for were more
significant in the less crystalline oxides. The Fe oxides crystallography referred to the greater
occurrence of goethite (Gt) in comparison to the hematite (Hm), corroborating the results
identified in the reflexes of the x-ray diffractograms. The isomorphic substitution (SI) was more
expressive in Gt, and the predominance of widths at higher half (LMA) in these oxides indicated
their lower degree of crystallinity compared to Hm. The average crystal diameters (DMC)
indicated higher crystal occurrence in Hm, but with lower abundance compared to Gt. The
higher values of the Gt / Gt + Hm ratio in the more superficial portion indicate there is a Gt
formation promotion at this depth. It was verified a disordered Kt expressiveness in relation to
more crystalline forms. In the two layers there were no distinctions between treatments with
respect to the development of Kt crystals. The SC treatment showed the soil losses effect on Kt
expressiveness, Kt IC and 2: 1 minerals.