How does the geographic location and pest management strategies impacts the geochemical fingerprint of leaves and olives in olive growing systems?

Recently, the demand for quality and food safety has become more pressing, with a consequent requirement for unequivocal geographical identification of agri-food products. Moreover, the requirement for eco-friendly and human healthy practices is a key issue for the agriculture of the future. In this framework, this work aims at investigating soil, leaves and olives from two areas in the Emilia-Romagna Region (Italy), Montiano (MN) and San Lazzaro (SL), where three different foliar treatments were carried out for each site to protect plants from environmental stress and pests. Geochemical analysis of REE and trace elements were performed to 1) univocally determine the locality of provenance and 2) evaluate if the different foliar treatments can affect the geochemical fingerprint of leaves and olives. the effect of different foliar treatments (no treatment, dimethoate, and alternating of natural zeolitite and dimethoate in MN; Spinosad+Spyntor fly, natural zeolitite and NH₄⁺-enriched zeolitite in SL). Principal Component Analysis (PCA) and Partial Least Square-Discriminant Analysis (PLS-DA, including Variable Importance in the Projection analysis) were used to discriminate between localities and different treatments. PCA of leaves and olives highlighted that different foliar treatments can be identified based on different geochemical contents (total variance: 95.64% and 91.08% in MN; 71.31% and 85.33% in SL of leaves and olives, respectively). Slightly lower, although still quite acceptable, results are given by PCA applied to area discrimination (87.46% and 80.43% of total variance). The PLS-DA analysis gave the largest contribution to the discrimination of different treatments and geographical identification. VIP analyses provided to identify which elements could be considered as potential discriminators in the model in order to correlate leaves and olives from the same area: i) Sm and Dy in MN site and ii) Rb, Zr, La and Th in SL field; in order to discriminate different areas Rb and Sr were the best identifiers. Based on REE and trace element analyses, it can be highlighted that 1) the geographical origin could be discriminated and 2) different foliar treatments applied for crop protection can be recognized, which means, reversing the reasoning that each farmer can develop a method to pinpoint his own product.