Global applications of the Visual Evaluation of Soil Structure method: A systematic review and meta-analysis

The Visual Evaluation of Soil Structure (VESS) method has been used frequently to evaluate the structural quality of soils from various parts of the planet, under different edaphoclimatic conditions and cultivation practices. In this context, this paper hypothesised that VESS is sensitive enough to detect differences between structural quality (Sq) scores of VESS from soils with different textural classes, submitted to distinct management and cultivation practices, under contrasting climates. To test this hypothesis, a systematic review and meta analysis of global scope were conducted, with the objective of compiling and analysing all indexed scientific papers that utilised the method. Exclusion criteria were adopted with the intention of eliminating papers that did not meet the selection criteria for the meta-analysis, however, these papers were used in the systematic review. A sensitivity analysis was performed prior to the meta-analysis in order to evaluate the heterogeneity in the data set, thus increasing the scientific validity of the overall analysis. The results obtained through the systematic review showed that the number of studies using VESS has grown in recent years, not only in temperate regions, but also under diverse soil conditions and cropping systems in subtropical and tropical regions. The meta-analysis showed that temperate soils presented lower Sq scores compared to those observed in tropical and subtropical soils, whereas higher Sq scores were observed in clayey/silty soils compared to sandy soils, regardless of climate zone. Our findings also revealed that Sq scores differences induced by soil management and cropping systems were not detected by the meta-analysis. Thus, the VESS is an on-farm, practical and reliable tool for evaluating the structural quality of soils globally.