Characterisation of viticultural and oenological practices in two French AOC in the middle Loire Valley: comparison of different methods to extract information from a survey among winegrowers

The type of wine is determined by environmental, plant materials and human factors. These factors are numerous and interact together, which makes it difficult to determine the hierarchy of their effects. We propose in this paper two methods to determine a hierarchy for these variables or their modalities. Using an inventory of agricultural, viticultural and oenological practices that are utilized for the production of Anjou Villages Brissac (AVB) or Anjou Rouges (AR) wines, it was attempted to determine for each of the variables whether their use differed significantly between the two appellations, and subsequently which of these practices were specific to each of the appellations.
Firstly, the variables and variable modalities were differentiated by a khi-squared distribution method. The database of the plots helped us to identify the practices which were used. An extraction of these plots was performed and the practices were classified by expertise.
Secondly, Classification and Regression Trees (CART) were used. This statistical method is non-parametric and non-linear and can, therefore, accommodate both continuous and categorical predictor variables. Variables can also be ranked in terms of their potential effect or relative importance. Using CART, the relative importance of each environmental, agricultural, viticultural and oenological variable in predicting whether a wine belonged to the appellation AVB or AR was determined and a final decision tree was constructed.
The final classification of variables using these different methods was compared and the observed differences were analysed. It remains to validate the hierarchical classification of the variables by means of experimentation with different technical itineraries on reference vineyards.