Comparison of LUCAS and Italian Sampling Procedures for Harmonising Physicochemical and Biological Soil Health Indicators

Abstract

Comparability of soil data derived from different sources is crucial to obtain consistent results when evaluating the soil health status. Discrepancies may arise due to various factors, including uncertainties resulting from different sampling methods. In this study, we compared various soil Physicochemical properties (ST)—pH, organic carbon, texture, cation exchange capacity, nutrients, heavy metals—and microbial diversity (BIO) of samples collected following both the LUCAS Soil (performed by the European Commission Joint Research Centre, JRC) and the Italian (performed by two regional agencies) procedures. The aim was to evaluate the effect of applying different soil sampling protocols on ST and BIO data. Soil samples from 58 LUCAS Soil 2022 sampling sites located in northern Italy were collected following both sampling protocols. Data obtained from ST analyses highlighted that the LUCAS and Italian protocols are comparable for most of the soil properties. Nevertheless, results can differ significantly depending on the parameter being considered, as evidenced by the concordance index varying from 0.37 to 1. Concerning BIO analyses, although the investigation of the microbial diversity indicators did not show a good concordance between the two sampling strategies, an analysis of the community structure highlighted a good correlation (Pearson's R > 0.6). An effect of the different land cover was observed for both ST and BIO analyses, suggesting that this could be a parameter to be considered when combining soil data obtained by different sampling protocols. Also, fungal communities showed lower concordance between LUCAS and Italian samples, highlighting a higher heterogeneity and a minor replicability with respect to bacteria and ST soil properties. In conclusion, this comparison generally showed consistency among the two sampling methods, suggesting that an integration of data from different sources is indeed possible for most of the parameters being analysed. However, further research is needed to obtain a sufficient level of harmonisation between LUCAS Soil and Italian sampling procedures for those soil properties for which a significant discordance was found.