Defining soil geochemical domains for terroir microzonation and sustainable, climate-resilient vineyard management

Climate change is intensifying drought and altering nutrient dynamics in vineyards, yet management within a single terroir remains largely uniform, ignoring the soil geochemical heterogeneity that governs water and nutrient supply. Mapping this heterogeneity is therefore a pressing but underexplored need. This study introduces a reproducible workflow that delineates soil geochemical domains from pre-existing geochemical data and links them to soil quality, turning a static database into an actionable tool for site-specific vineyard management in the Taurasi terroir (southern Italy), renowned for its high-quality wines. Compositional data analysis, robust principal component analysis, and K-means clustering were applied to 102 topsoil samples (10 elements) to identify domains, which were mapped using Thiessen polygons. New samples collected from the same sites provided data on pH, organic carbon, and grain size, which were integrated into a weighted Soil Quality Index (SQI). Three domains were identified: carbonate (49% of samples; 132 km²), volcanic (39% of samples; 109.4 km²) and weathered (12% of samples; 33.3 km²). Volcanic soils showed the highest levels of organic carbon (median 3.51%), K (13,400 mg/kg), P (1205 mg/kg), and B (16 mg/kg), a coarse texture, and a near-optimal pH (median 6.68), resulting in the highest SQI (median 0.40). Carbonate soils, despite their high Ca content (60,600 mg/kg), had an alkaline pH (median 8.07), which limited the availability of P and K (SQI 0.22), whereas weathered soils were nutrient-poor and fine textured (SQI 0.18). These differences imply different potential nutrient supply and drought resilience across the various domains. We conclude that mapping geochemical domains is a fundamental tool for sustainable viticulture and recommend prioritizing the planting of new vineyards on volcanic soils to reduce fertilizer inputs and mitigate water stress under climate change.