Atributos físicos e mecânicos de agregados de latossolos vermelhos sob distintos sistemas de uso e manejo

Abstract

There is a need to assess and study the physical and mechanical behavior of soil at the macroscale and the changes that occur in this structure. The implementation of land use systems and soil management is related to the study of physical and mechanical attributes of individual soil aggregates. Thus, the objective was to study and quantify, through individual aggregates, the physical and structural changes occurring in soils under different land use systems and management as well as evaluating the influence of sampling positions on the row and interrow cultivation on a soil under no-tillage. For this purpose three studies were developed in two soils belonging to the class of Oxisols, so this work is organized into three chapters. The first study aimed to evaluate the effect of different land use and management systems (no-tillage, pasture and native forest) on some physical (density of aggregates - ρagg) and mechanical attributes (tensile strength of aggregates - TS and friability of soil - F) in an Oxisol. Measurements of organic carbon in aggregates were also made. The second study aimed to evaluate the effect of different sampling positions on TS, F, SOC and ρagg in an Oxisol under no-tillage (NT). The third study aimed to evaluate the long-term impact of the NT on the soil structure, as a comparison with a soil under native forest. Both the study 1 and 3, TS was evaluated in different sizes of aggregates while in study 2 assessments were made in aggregates with size from 12.5 to 19,0 mm. The results indicated that the reduction of the diameter of the aggregates showed an increase on the values of tensile strength of aggregates (TS). The highest values of TS in pasture result from the higher density of the aggregates. In assessing the relative effect of sampling position, the results showed that at 0-10 cm were the highest values of F in position relative to the crop rows and there were no differences in TS between the sampling positions in the 0 - 10 cm. The ρagg and SOC did not differ between the sampling positions, distinguishing only between the layers. In the soil under native forest, study 3, the highest TS values observed are consistent with the highest level of SOC, probably due to the effect of cement SOC with a reduction in aggregate size. In general, we observed a decrease in the forest soil ρagg when compared to native soil under NT as well as aggregates showed higher levels of SOC, differing from the NT.