Identification of environmental factors controlling wine quality: A case study in Saint-Emilion Grand Cru appellation, France.

Soil is a key component of the terroir concept for wine production. Indeed, the soil provides water and nutrients to the vine plants depending on its properties and environmental conditions. A part of the complexity in the production of high-quality wines is the adaptation of the winegrowing practices to soil conditions variability in space and time. Then, a deep understanding of the environmental conditions that modulate soil-plant system functioning and control the production of quality wine is crucial for future global change adaptation. This study aimed to identify environmental factors controlling red wine quality by merging both winemaker and scientist knowledge. This work was performed on a vineyard in Saint-Emilion Grand Cru appellation, France. First, we conducted field investigations for micro-terroir scale soil mapping in 2017, based on pedological prospections (pits and auger borings) and both water table levels and main meteorological parameters monitoring (from November 2017 to November 2018). Additionally, we collected for each vineyard plot the corresponding wine quality rank established each year since 2012 and based on wine tasting sessions supervised by the winemakers. Subsequently we investigated both nutrients and water availability for the vine. This was achieved through correlative analysis using soil description, roots observation and water table level, stratified according to both soil functional units and wine quality ranks maps. Results show that the water table dynamic and the soil texture have a major impact on the root pattern of vines. Our study suggests that explanatory factors for wine quality are interactions between soil-water and roots during vine crop season. Here, best soils for fine wines could be observed for both non-severe water deficit and no-limited nutrient conditions.