No abstract

The objective of this study was to evaluate the physical attributes of an oxisol under soybean monoculture, eucalyptus monoculture, and pasture and native forest conditions at depths of 0-0.20 and 0.20-0.40 m. Disturbed and undisturbed soil samples were collected to perform physical analyses. Specific analyses included texture, soil density, macroporosity, microporosity, total porosity, aggregate stability index, weighted mean diameter, percentage of aggregates with a diameter of >2.00 mm, and soil penetration resistance (PR). The data were analyzed using the Tukey's test for the comparison of mean values and multivariate analysis. Different uses and management of the soil affected its physical attributes, resulting in the deterioration of soil quality in the soybean and pasture areas. Soil management systems in pasture and soybean areas also resulted in higher soil density and lower soil porosity. The eucalyptus monoculture showed soil aggregation equal to that of the native forest. There was a sharp increase in soil PR beyond the 0.15-m deep layer in the pasture and soybean management systems. Multivariate analysis identified variables that correlated with each type of soil management and the effects of changes in soil characteristics.

RESUMO:Brazilian agriculture has been highlighted in Savanna areas due to significant gains in production and productivity in this biome. However, the production model with intensive use of machines for several years causes drastic changes in soil physical quality. This study aimed to investigate the influence of conventional management adoption time in a Yellow Oxissol on soil physical properties. Soil density, particle density, total porosity and soil resistance to penetration were assessed in areas under conventional management, in different usage times, in comparison to a native Savanna, which was used as control. The areas under conventional management contributed to increase the density and reduce the porosity, which was intensified with time of soil use. In the 6 years area, the porosity showed values below 0.50 m 3 m -3 in the two measured layers. Higher penetration resistance values were observed to areas with higher use of time from 0.15 m depth, reaching values above 3.0 and 2.0 MPa in soils with 6 and 3 years of use, respectively, which is ranked as high. The native vegetation and the newly deforested area have provided less resistance to penetration along the profile, with values falling into low and moderate classes. Different time periods since the implementation of soil management were differentiated by the physical properties of studied soils.

Scarification improves soil physical conditions, resulting in suitable conditions for root growth in crops and water infiltration. This study evaluates the effects of mechanical scarification on the physical attributes of a Yellow Oxisol cultivated with soybean under no-tillage in the Savanna of Piauí state, Brazil. Three areas under soybean cultivation were chosen, namely: one in the second year of cultivation under no-tillage (CS2); one cultivated for ten years under no-tillage (CS10); one area with soybeans identical to the previous one, but with scarification for a year (ESC); and a native Savana vegetation (CV), used as control. Density, macroporosity, microporosity, total porosity, and soil resistance to penetration at depths between 0-0.20 and 0.20-0.40 m were evaluated. The CS area showed decreased physical indicator values compared to the other management systems. Scarification was efficient in improving soil density, total porosity, and soil resistance to penetration at depths between 0.00 and 0.20 m. CS2 and CV areas showed more favorable physical indicator values. Through multivariate analyses, it was possible to identify which physical variables correlated with each type of soil management and the effects of these managements on the physical characteristics of the soil studied.