Harnessing soil geochemistry and granulometry for optimal terroir management and wine profiling: insights from the Taurasi terroir of southern Italy

The interaction between the unique geochemical characteristics of the soils and the social, environmental, climatic and biodiversity factors give distinctive properties to the wines of a specific area, defining the terroir of a wine. While climatic, ecological, and social aspects remain relatively stable within the limited extension of terroirs, soil geochemistry can change notably. Variations in soil geochemistry play a significant role as they influence vine health, grape quality and, ultimately, the flavour profile of the wine. This study aims to highlight the chemical and granulometric differences occurring in the Taurasi terroir (Southern Italy) to improve its management and enhance the diverse flavours and aromas of the wines. The Taurasi terroir encompasses an area of 245 km², within which soils belong to three different geochemical domains (clay, volcanic, and carbonate soils). Chemical elements affecting colour and aroma (Cu, Fe), taste (Na, K), metabolism and photosynthesis (B, Mn, Zn), or potentially toxic elements for vines (Al, As) were analysed in 100 topsoil samples distributed across the three geochemical domains. Additionally, granulometry and organic carbon content were also analysed to assess soil's ability to retain water and microbial populations. Results revealed significant compositional differences among the three geochemical domains that inevitably reflect in wine characteristics. Except for Mn, volcanic soils were enriched in all analysed elements, while carbonate soils were depleted. Following the order of volcanic soils – clay soils – carbonate soils, the average concentrations of analysed elements were as follows: As (16 - 7 - 3 mg/kg); Al (5.5 - 3.2 - 1.8 %); B (24 - 10 - 6 mg/kg); Cu (78 - 52 - 28 mg/kg); Fe (3.2 - 2.7 - 1.8 %); K (1.6 - 0.7 - 0.4 %); Mn (950 - 1470 - 820); Na (0.6 - 0.05 - 0.05 %); Zn (105 - 62 – 58 mg/kg). From a granulometric perspective, volcanic soils were coarse-grained, followed by carbonate and clay soils. The average granulometry for the three geochemical domains is as follows: volcanic soils (72% sand, 13% silt, 5% clay); carbonate soils (26% sand, 58% silt, 16% clay); clay soils (5% sand, 13% silt, 72% clay). Average organic carbon values were also favourable for volcanic soils (4.5%), followed by carbonate soils (3.2%) and clay soils (1.4%). These results show that significant compositional and granulometric differences within the Taurasi terroir are reflected in the expression of grapes and wines produced. Therefore, this study provides key tools for micro-zoning terroirs to enhance diverse flavour, colour, and aroma expressions within the same terroir.