Evolução de feições erosivas na microbacia do Córrego Boa Vista Prata/MG

Abstract

The region of Serra da Boa Vista, situated in the Triângulo Mineiro/MG, is characterized by residual relives of formations Marília and Adamantina. Not different of other areas that develop farming activities of Brazil, the use of the ground resulted in some environmental problems. The erosion of the soil manifest as the biggest problem for the people who make the use of the land, and is between the greaters causes of economic and environmental damages, in reason of the impossibility of use of extensive areas and devaluates the property. The objective of the work was to characterize and to evaluate the responsible factors for the development of erosive aspects (gullies) in an area delimited for this end, located in the Serra da Boa Vista, delimited for the geographic coordinates 19º29' 14.0 of south latitude/ 49º12' 56.2 of longitude west. Surveys of field, assays of laboratory in mechanics of ground and of field (in situ) had been realized in the attempt to understand the responsible factors and processes for the development of these erosive aspects. Results of grain sized analyses of the soil, had evidenced an interval between 49,2% and 73,3% of Sand, 14.9% and 26.3% of Silte and 11.8% and 27.1% of Clay. Permeability tests realized in situ, with use of the Guelph Infiltrometer, got values of coefficients of permeability (k) relatively raised, in order of 10-3 cm/s. The accomplishment of the consolidation test made possible the gain of the porosity (η) of the soil and its void ratio. The use of the Blue one of Methylene for attainment of the Cationic Exchange Capacity (EC) and of the Specific Surface (SS), evidenced relatively high values of the EC in samples of the right side of the erosion in reason of the raised rate of present organic substance in the superficial layers of the ground soil samples of the left side had presented inferior values. The erodibility of the soil was quantified by means of the water absorption test and Loss of Mass for Immersion, the gotten results presents a high dispersibility of the soil when immersed of water. From the data of field and laboratory tests, it can be affirmed that the origin and evolution of the erosive aspects (gullies) in the studied area, suffer effect from natural factors and antropogenics antagonistics: of one side, the ones that premake the erosion (soil of arenaceous characteristics, accented declivity, use of the ground with the withdrawal of the original natural covering, superficial draining of raised energy proceeding from the portions of top of the residual ones); of the other, the ones that tend to give stability to the soil (presence of the organic substance that, in set with the grassy roots, adds the soil of the superficial portion of the profile).