Soil and Climate Interactions with Grapevines

To test the hypothesis that soil type plays a minor role relative to that of vine vigor in the determination of yield, fruit composition and wine sensory attributes, 5 Chardonnay vineyards in the Niagara Peninsula of Ontario were chosen for study. These vineyards were located on sites with heterogeneous soil types to allow study of the impact upon yield, fruit composition and wine sensory attributes of: 1. Soil texture with mesoclimate kept constant; 2. The comparative magnitude of effects of soil texture, vine vigor, and crop size. Vineyard blocks were delineated using global positioning systems, and a series of 72-162 data vines per site were geo-located within a sampling grid imposed on each vineyard block. Data were collected on soil texture, soil composition, tissue elemental composition, vine performance (yield components and weight of cane prunings), and fruit composition. These variables were mapped using geographical information systems and relationships between them were elucidated. Soil texture and composition were frequently correlated to yield components and fruit composition but often relationships were site-specific. Spatial correlations were common between % sand, vine size, yield, berry weight, soluble solids (Brix), and titratable acidity (TA); however, these relationships were vineyard and vintage dependent. Several spatial relationships were apparent between vine size, yield, Brix, TA and many soil and petiole composition variables, including organic matter, soil pH, cation exchange capacity, and soil/petiole N, P, K, Ca, Mg, and B. Spatial relationships between yield, berry weight, berry composition, vine size, and several soil physical and composition variables suggests a likely soil basis to the so-called “terroir effect”.