Characterization of viticultural terroirs using a simple field model based on soil depth I. Validation of the water supply regime, phenology and vine vigour, in the Anjou vineyard (France)

The soil and climate in which grapes are grown play a major role in the vine behaviour, grape quality and wine sensory characteristics. In France, these factors are often integrated in the concept of "Terroir", which is a topic of growing interest in wine producing countries. The application of this concept requires a scientific approach of the "Terroir climatic and pedoclimatic components" to achieve a rigorous zoning of vineyards. In this paper, results concerning the testing of a method developed in the Anjou vineyard (France) to characterize viticultural terroirs, are presented and discussed. This method uses a field soil model based on the type of parent rock, the depth and the clay richness of soil, mainly in connection with the weathering level of the parent rock. For each geological stage and each type of rock, this easy-to-use model makes it possible to identify three types of soil named: Weakly Weathered Rock (WWR), Moderately Weathered Rock (MWR) and Strongly Weathered Rock (SWR). Each terroir unit obtained by this method can represent a "functional" unit of vine, from the ecophysiological and environmental point of view. To verify this hypothesis, experimental plots planted with Chenin and Cabernet Franc varieties were studied over three consecutive seasons (2000-2002). The main results on vine water supply, burst, and timing of veraison show significant differences, in particular between WWR and SWR. However no significant differences in pruning weight were observed, probably because of high rainfall during all three growing seasons.