Compressibility Parameters Associated to State of Soil Compaction and Moisture of Two Oxisols

Abstract

ABSTRACT Improving and preserving soil quality in areas managed under no-tillage, especially in clayey soils, is extremely important for achieving high productivity along with environmental preservation. In this study, we evaluated the effect of three states of soil compaction and initial water saturation on pre-consolidation pressure (σp) and compaction index (CI) of two Oxisols, in order to estimate maximum loads to be applied by pneumatic machinery and agricultural implements without causing irreversible damage to soil structure. Oxisol-LVd (0.55 kg kg−1 clay) and Oxisol-LVdf (0.62 kg kg−1 clay) soils from the plateau region of Rio Grande do Sul were studied. An isoline map was generated for soil penetration resistance in the 0.07–0.12 m soil layer, with the highest state of compaction. Soil bulk density was used to characterize three state of compaction, used as treatments. Statistical analysis consisted of comparing soil σp and CI means for state of compaction, initial water saturation, and soil layers. Increase in clay content and bulk density and reduction in soil moisture is associated with increase in soil σp and decrease in CI. Average values of critical σp of the three states of compaction at field capacity are 245 kPa for Lvd, and 347 kPa for LVdf. In an annual timeframe for already consolidated no-tillage Oxisols, further soil wheeling and natural reconsolidation does not affect soil pre-consolidation and compaction susceptibility.