Soil physical quality using DRES and VESS visual assessment approaches and physical properties

Soil structure evaluation is one of the main tools for diagnosing changes in soil physical quality under contrasting land-use systems. Visual assessment methods have been proposed as a low cost and practical alternative to traditional methods for evaluating soil structural quality. The Rapid Diagnosis of Soil Structure (DRES) is one of the most recent visual methods proposed for assessing the structural condition of tropical soils. It is supposed to improve on other methods by setting a lower soil aggregates diameter limit for soils with good structural quality. There are few publications which assess its performance and correspondence to other soil physical properties. Thus, this study evaluated the structural quality of an Oxisol (Typic Haplustox) under pasture system (PS), silage corn under direct seeding (DS), banana orchard (BA) and native vegetation Cerrado (CN) using the DRES methodology. In addition, we correlated the scores of the visual analysis with the soil physical properties bulk density (BD), total porosity (TP), soil penetration resistance (SPR), soil penetration resistance corrected to the field capacity (SPR_FC), weighted average diameter of aggregates (WAD), soil organic matter (OM) and parameters of the water retention curve (WRC). A comparison was also made between DRES and the Visual Evaluation of Soil Structure (VESS) methodology. The soil under PS and DS showed the lowest scores for the DRES, and consequently the worst structural soil quality condition. The physical properties BD, TP, SPR, microporosity (MICRO) and macroporosity (MACRO) showed significant correlation with the visual analysis scores obtained using DRES and VESS. In general, DRES distinguished the soil structural quality under different land-use systems and can be considered a promising semi-quantitative method in diagnosing soil structural quality. However, even though DRES and VESS scored similarly in this study, there are possible critical incompatibilities between the two systems regarding diameter of aggregates that need to be addressed in further studies.