Characterization of grumusols of southwestern Rio Grande do Sul. I. Physical properties limiting their use

Abstract

A study of the physical properties that made cultivation difficult were made on five pedons of the soil units of Bagé, São Gabriel, Piraí, Hulha Negra and Aceguá. With the exception of the São Gabriel soil, they have been classified provisionally as Grumusols by the Division of Pedology and Soil Fertility. These soils occur in the central depression of Rio Grande do Sul on clays and silts of the geological groups Passa-Dois and Tubarão. All of the soils had the following characteristics: (a) indication of high plasticity, being classified as materials with limitations for engineering work; (b) high bulk density and low porosity; (c) high volumetric expansion (up to 59%); (d) fine granulares being specially high in fine clay (< 0,2 micron). Some pratical recommendations are suggested based on the limitations of the physical properties of these soils for cultivations.