Knowledge on soil shear strength can actually be a very useful tool for the control of slope and gully erosion, as well as for the introduction of mechanical conservation practices in agricultural soils. In order to evaluate the shear strength of five soils in the region of Lavras (MG) and its relation with the weathering rate, an experiment was carried out, using a direct shear machine which allows the collection of undisturbed soil samples. These samples were collected at a depth between 0 and 0.03 m and subjected to the shear strength treatment for the definition of rupture line and the obtainment of the apparent cohesion (c) and the internal friction angle (φ). In general, c was higher in soils which presented a higher density, humidity/moisture at -0.01 MPa and a higher sand content. The (φ) values were higher in soils with higher clay contents. The distrophic Red-Yellow Latosol (dRYL) and the typical distrophic Red-Yellow Utisol (tdRYU) with greater soil densities, sand contents and moisture at -0.01 MPa, presented higher shear strength than the distrophic Red Latosol (dRL), distrophic Inceptsoil (dI) and distroferric Red Latosol (dRL), which contained higher contents of clay and organic matter. For Latosols, the soil shear strength was higher where Ki and Kr indices increased, due to the block structure of the dRYL, causing elevated shear strength. In relation to shear strength, the dRYL and the tdRYU proved to be more resistant to gully erosion and tillage practices.
soil conservation; structure; texture; bulk density; erosion