Use of GPS and GIS for Elucidation of the Basis for Terroir: Spatial Variation in an Ontario Riesling Vineyard

Abstract

Vine size and soil texture effects on yield components, soil, vine tissue, fruit composition, and wine sensory attributes were measured in an Ontario Riesling vineyard to clarify the potential basis for terroir. Sentinel (sample) vines were geolocated using global positioning systems. Geographic information systems delineated spatial variation in soil texture and soil vine tissue composition (1998) and in yield components, berry composition, and weight of cane prunings (vine size) over four years (1998 to 2002) from each sentinel vine. Vines were classified as large or small based on previous season vine size within each of two soil texture classes (clay and sand); fruit from these four categories was separated for winemaking; berry, must, and wine chemical compositional data were determined; and wine sensory descriptive analysis was conduced. Correlations were observed between soil texture and composition versus berry weight and potentially volatile terpenes (PVT). There were no consistent soil texture or vine size effects on berry, must, or wine composition. Large vine size increased berry titratable acidity (TA) (2001) and PVT (2002), decreased must pH (1999), and increased wine free volatile terpenes (2001). Sandy soil reduced wine TA and must PVT (1999) and increased berry TA and must soluble solids (2002). Vine size and soil texture did not consistently affect wine sensory attributes across vintages. High vine vigor decreased mineral aroma (1999) and citrus flavor (2001) and increased apple attributes (2001). Clay soil increased mineral aroma (1999 and 2001) and citrus attributes (1999) but decreased apple aroma (1999). Citrus aroma and petrol flavor increased in some vine size x soil texture combinations in 2002. Vintage and wine age had greater impacts on wine sensory attributes than vine size or soil texture.