Sustainable yield management through fruitfulness and bunch architecture manipulation

“The vine and the wine are great mysteries. Only the vine makes us intelligible what is the true flavor of the earth”. Colette. The notion of terroir has always been the basis of the notion of AOC from which it is inseparable. It is moreover the definition of the production zone which was at the start of the attempts to set up the designation of origin, at the beginning of the century, after the phylloxera crisis.

Viticulture on steep slopes has shaped exceptionally species-rich cultural landscapes in Germany.

Drought poses a challenge to future viticulture, exacerbated by climate change, which increases the frequency and severity of water shortages.

Recently, the European Commission seems to have inaugurated a new mechanism for regulating the wine sector. Through two communications, articulated in the form of “Questions & Answers”, concerning the new rules for labeling (24.11.2023) and dealcoholization of wine (15.01.2024), the Commission is not simply “explaining” the new rules but, in an approach close to the theory of “Circulaire Normative” established in comparative law, chooses among different interpretations and even adds Praeter Legem constraints.

The current climate changes are directly threatening the balance of the vineyard at harvest time. The maturation period of the grapes is shifted to the middle of the summer, at a time when radiation and air temperature are at their maximum. In this context, the implementation of corrective practices becomes problematic. Unfortunately, our knowledge of the climate effect on the quality of different grape varieties remains very incomplete to guide these choices. During the Innovine project, original experiments were carried out on Syrah to study the combined effects of normal or high air temperature and varying degrees of exposure of the berries to the sun. Berries subjected to these different conditions were sampled and analyzed throughout the maturation period. Several quality characteristics were determined, including anthocyanin content. The objective of the experiments was to investigate which climatic determinants were most important for anthocyanin accumulation in the berries. Temperature and irradiance data, observed over time with a very thin discretization step, are called functional data in statistics. We developed the procedure SpiceFP (Sparse and Structured Procedure to Identify Combined Effects of Functional Predictors) to explain the variations of a scalar response variable (a grape berry quality variable for example) by two or three functional predictors (as temperature and irradiance) in a context of joint influence of these predictors. Particular attention was paid to the interpretability of the results. Analysis of the data using SpiceFP identified a negative impact of morning combinations of low irradiance (lower than about 100 μmol m−2 s−1 or 45 μmol m−2 s−1 depending on the advanced-delayed state of the berries) and high temperature (higher than 25oC). A slight difference associated with overnight temperature occurred between these effects identified in the morning.