Validation of the soil Biological Fertility Index (BFI) using a multidimensional statistical approach: A country-scale exercise

The soil Biological Fertility Index (BFI) is an indicator system recently proposed to monitoring soil fertility in Italy by composing 6 biological variables derived from field sampling and standard laboratory analysis. Large-scale validation of the BFI is still lacking. By using parametric/non-parametric correlations and multivariate statistical analysis, this study compares the statistical distribution of the BFI over 1079 soil samples representative of various environmental contexts in Italy with 8 alternative indicators formulated according to different aggregation rules and weighting techniques of the 6 variables composing the BFI. Our results demonstrate that the BFI is stable to changes in the composing variables, aggregation rules and weighting techniques, confirming its appropriateness as a multi-domain indicator of biological fertility specifically designed for assessment of Italian soils.