The performance of grapevines on identified terroirs in Stellenbosch, South Africa

A terroir can be defined as a natural unit that is characterised by a specific agricultural potential, which is imparted by natural environmental features, and is reflected in the characteristics of the final product. Preliminary terroirs were defined for Stellenbosch for Sauvignon blanc and Cabernet Sauvignon using decision trees built on analyses of viticultural, oenological and environmental data measured on a network of plots over 7 seasons. This study was considered to be a preliminary approach to determine the validity of terroir studies for the South African wine industry.
It was expected that measurement of viticultural and oenological variables would serve to validate or refine the decision trees constructed with the first set of data and that the measurement of ecophysiological parameters on a separate network of reference plots would facilitate improved understanding of the grapevine x terroir interaction. Three plots of 10 vines each were therefore identified in selected commercial vineyards of Cabernet Sauvignon and Sauvignon blanc using remote sensing as a tool to identify homogenous plots where possible. These vineyards were representative of dominant terroir units that were identified for each cultivar. This network of experimental plots was monitored with respect to their ecophysiological response to the growing environment. This included dynamics of canopy development, vegetative growth, dynamics of berry growth and composition and wine character. Pre-dawn leaf water potential was determined at different stages during the growth season. The growing environment was characterised with respect to soil and climate by means of direct observations and measurements and interpolated values from the agroclimatic weather station network.
This paper will examine the results from three seasons for selected Sauvignon blanc and Cabernet Sauvignon vineyards from this network and compare these results to previous findings.