Indicadores de qualidade física para Argissolos sob pastagens nas regiões leste e sul de Minas Gerais

Abstract

This research has been conducted in Argissolo areas in the Eastern and Southern Regions of Minas Gerais with the aim of evaluating the physical quality of the topsoil of this area, basing the results on Water Retention Curves (WRC) and using the secondary native forest as a reference. A completely randomized experimental design has been used for this purpose, with 4 management systems (South Pastures of Minas Gerais, East Pastures of Minas Gerais under regular grazing pressure, East Pastures under High grazing pressure and Native Forest) in 3 repetitions, totalizing 12 samples. To obtain the WRC, the undisturbed samples were prepared and subjected to matric potentials of -2, -4, -6, -8 e -10 kPa for suction units and of -33, -100, -500 e -1500 kPa for Richards chambers. The soil density (SD) was determined by the volumetric ring method. The attributes indicating the physic quality of the soil were calculated using the WRC: micro and macro-porosity, total porosity, available water capacity, pore distribution size and S index. The soil under native forest showed better structural quality that soils managed with grazing. In the Eastern region of Minas Gerais, land use with grassland under strong pressure of grazing caused degradation of soil structure, evidenced by the physical quality indicators extracted from the WRC: S index and pore distribution size. The S index values were higher in managements Forest and South Pasture Minas Gerais, indicating better structural soil conditions in these environments.