Study of the “Charentes terroir” for wine production of Merlot and Sauvignon: method, installation of the experimental device, first results

Cognac vineyard is mainly dedicated to brandy production. Within the vineyard restructuring context, one part is turned over wine varieties for wine production (about 1,500 ha planted from 1999 to 2005). Today, the new wine producers need technical references about qualitative potential of the « Charentes Terroir », varieties and adapted vineyard management. In order to answer to this professional request, an observatory of 18 plots of Merlot and 12 plots of Sauvignon have been laid out since 2003 and 2004 on various kinds of pedoclimate. They have common agronomical characteristics, as plantation spacing (3,800 to 5,000 vines per ha), age (plantation from 1998 to 2001), strength and earliness conferred by the rootstocks, soil management and trellising (« guyot double » pruning). A pedological and roots description, analysis of the different horizons and a water reserves evaluation have been made to characterize the soils. A synthetic pedological plots study validates the experimental device as a representative sample of the agro-pedological vineyard diversity.
Vine behaviour and oenological potential of each plot is studied: phenological stages, growth stop, canopy area, maturity controls, Delta C13. More, the technical team controls the yield by pruning, desuckering and green harvests. Harvest from each plot is vinificated according to a standard protocol. An expert panel tastes wines.
First results show an important climate effect on the west part of the vineyard and an earliness differential for phenological stages and ripeness. However, 3 years of results are too short to conclude definitely because millesime effect is important for the years 2003 to 2005. Thus, one or two more years’ observations will complete this work and several methods of vineyard management will increase the experimentation. The aim is to adapt the wine production to the « terroir » potential.