Different physical properties are used to evaluate the soil physical quality. In this context, soil tensile strength and friability are indicators of the soil physical and structural quality. The objective of this study was to quantify the tensile strength and friability of an Oxisol under different soil use systems: forest, fallow and cultivated. Soil samples were collected from three contiguous areas of an Experimental Farm of the State University of Maringá. Two areas were cultivated: one with annual crops under conventional tillage (disk plow and harrowing) and another under fallow with forage grass. Soil without cultivation under native forest (semidecidual seasonal forest) was used as reference. In 2006, ten blocks (undisturbed soil samples) were collected in each treatment at 0-0.15 m depth. In each treatment, the tensile strength of 400 aggregates with 12.5-19.0 mm diameter was measured, as well as soil organic carbon and bulk density. Soil friability was estimated by the variation coefficient of tensile strength. In this soil, tensile strength increased proportionally with the decrease in soil organic carbon. Soil friability was classified as independent of the soil use system. Soil friability was higher under forest than in fallow and cultivated soils. The tensile strength, friability, soil organic carbon and soil bulk density expressed the decrease of soil quality associated with more intensive soil use systems. Tensile strength and soil friability demonstrated the effects of soil use systems in the soil physical and structural properties.
soil bulk density; soil management; soil organic carbon; soil quality
