ABSTRACT New management practices applied to coffee crops may influence the soil’s capacity to tolerate vertical stresses. This paper aimed to evaluate the influence of two coffee crop management systems on the soil load-bearing capacity and critical soil water content to agricultural machinery traffic. This study was performed in the experimental area of the Federal Institute of the Southeast of Minas Gerais - Rio Pomba college, in Rio Pomba city, Minas Gerais, Brazil. Dystrophic Red-Yellow Oxisol (Latossolo Vermelho-Amarelo distrófico) (LVA7) with clayed texture predominating in the experimental unit. Undisturbed soil samples were collected from layers of 0.00-0.03, 0.12-0.15 and 0.27-0.30 m, randomly, in the center of the interrows of coffee plants (Coffea arabica L.) in monoculture plots under traditional management (in full sun) and in the plots of coffee plants intercropped with gliricidia (Gliricidia sepium) (shaded) to estimate pre-consolidation pressures, through uniaxial compression tests and adjustment of soil load-bearing capacity models. The average and maximum normal stresses applied to the soil and the vertical stress distribution of three agricultural tractors used in mechanized farming operations were estimated, and the critical soil water content to the traffic of these tractors was determined for both treatments, aiding in the decision-making process regarding additional compaction risks in the area. Cultivation of gliricidia in consortium with coffee did not influence the soil load-bearing capacity. The soil layer of 0.12-0.15 m was the most vulnerable to vertical stresses in both treatments. Agricultural tractors Agrale 4100, MF 265 and MF 275 presented values of vertical stresses of 335.76, 200.24 and 245.55 kPa, respectively, and the soil water content for the traffic of agricultural machines without plastic deformation was higher in the coffee plants in full sun for all studied depths.

A distribuição de poros dos solos condiciona seu comportamento físico-hídrico. Assim, influencia os processos dinâmicos do ar e da solução do solo, bem como a potencialidade agrícola dos mesmos. Desta forma, com o presente trabalho, objetivou-se avaliar a influência da distribuição de poros sobre as propriedades físicas de seis classes de solos, sob vegetação natural, localizados na região de Lavras (MG). Coletaram-se amostras deformadas e indeformadas da camada superficial (0-20 cm) para a caracterização física e a determinação da curva de distribuição de poros dos solos. Os resultados indicaram que as propriedades físicas dos solos não foram influenciadas pelos poros com diâmetro entre 0,03 e 0,0375 mm. Verificou-se, também, que os valores de macroporosidade foram diretamente proporcionais aos valores de condutividade hidráulica saturada dos solos estudados.

The soil pores distribution conditions its physical-hydraulic behavior. Therefore, it influences the dynamic processes of air and solution of the soil, and also its agricultural potentiality. This work aimed at evaluating the influence of pores distribution on physical properties of six classes of soil, under natural vegetation, located in the region of Lavras (MG). Disturbed and undisturbed samples were collected from superficial layer (0-20 cm) for physical characterization and determination of pores distribution curves. The results indicated that soil physical properties were not influenced by the pores with diameter between 0,03 and 0,0375 mm. It was also verified that macroporosity values were directly proportional to the hydraulic conductivity values of saturated soils.

A permeabilidade do solo é um atributo físico de grande importância para a engenharia, sendo necessária a sua determinação nos trabalhos em que se tem movimento d´água no solo. Vários são os atributos físicos do solo que influenciam nos valores do seu coeficiente de permeabilidade, sendo considerados de maior importância a densidade e a porosidade. Neste trabalho, objetivou-se verificar as correlações existentes entre os atributos físicos do solo com a permeabilidade. Esses solos foram obtidos da sub-bacia do córrego Centenário, localizada na área urbana da cidade de Lavras, sul do Estado de Minas Gerais. Para a coleta desses solos, utilizou-se de um amostrador projetado especialmente para esta pesquisa, que apresentou uma boa eficiência na representatividade dos solos retirados. O atributo físico do solo que melhor se correlacionou com a permeabilidade foi a macroporosidade, verificando-se ainda boa correlação para a microporosidade, resistência à penetração e a densidade.

The permeability of the soil is a physical attribute of great importance for engineering, being necessary its determination in the works where it has water movement in the soil. Several are the physical attributes of the soil that have influence in the values of the coefficient of permeability, being considered the most important ones the density and the porosity. This paper aimed at verifing the existing correlation between different physical attributes of the soil with the permeability. These soils were removed of the sub-basin of the stream Centenário, located in the urban area of the Lavras city (Minas Gerais state, Brazil). For collecting those soils were used a sampler projected especially for this research, wich presented a good efficiency in the representation of removed soil, and comparing the results of the tests in laboratory with the field tests. The attribute of the soil that better correlated with the permeability was the macroporosity, verifying yet its good correlation concerning to the microporosity, resistance to the penetration and soil density.

Os solos porosos arenosos colapsíveis ocorrem na região central do Brasil, representando 5% da área do país. Esses coluviões porosos alcançam espessuras de até 15 metros. Nesse trabalho, foram construídas estacas pré-moldadas de concreto, instrumentadas, especialmente confeccionadas para essa pesquisa. Essas estacas foram cravadas em solo arenoso de alta porosidade, colapsível, situado na região oeste do Estado de São Paulo. Diversas provas de carga axiais, estáticas, foram efetuadas em seis estacas (por ensaios de compressão, tração e carregamento horizontal). Foram realizados, ainda, ensaios geotécnicos laboratoriais e de campo nesses solos, com o intuito de melhor caracterizar o campo experimental estudado.

Collapsibles porous sands are found to a large extent of Brazil, representing 5% of the country. In the layers of those soils the thickness are of to 15 meters. Precast-concrete piles were build, with instrumentation, made to that research. The piles were drive in soil sandy porous collapsible, found in the state of São Paulo (Brazil). Vertical static load tests were made in six piles (compression, uplift forces and horizontal loading). There were performed field tests and laboratory in samples obtained from the subsoil, aiming geotechnical characterization of the place.