Compaction of agricultural soils due to intensive farming with intense traffic of agricultural machinery has become a limiting factor for crop development in recent years. The objective of this study was to evaluate a Rhodic Acrustox under no-tillage for the influence of compaction on the soil density, porosity, penetration resistance and aggregate stability, and the consequences on corn root growth. Compaction was induced by tractor traffic of MF 292 (105 hp), with a mass of 5 Mg and pressure inflation of 96 kPa for front tires (14.9-24 R1) and 110 kPa for rear tires (18.4 - 34 R1) in the following treatments: NT - current condition that reflects the history of eight years of no-tillage, no-tillage with additional compaction by tractor traffic in one (NT - 1), two (NT - 2), four (NT - 4) and six passes (NT - 6). Soil microporosity was not affected by additional compaction. The root diameter, length and surface values were reduced, with a decrease of 85 % in root length of NT compared to NT - 6. Increased soil compaction induced by tractor traffic with two passes (220 kPa) or more increased soil density and reduced macroporosity and total porosity, while four passes (440 kPa) or more resulted in an increase in soil penetration resistance to a depth of 0.10 m. Macroporosity is a good indicator of soil quality in assessments of root length and surface.
physical properties; root length; root surface
