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This study highlights the physiological effects of pre-flowering leaf removal from the fruiting zone of the Swiss white grape variety Petite Arvine, which is rich in varietal thiols. Pre-flowering removal of main leaves instead of lateral shoots appears to be a viable practice with a moderate effect on both the yield potential and the must composition; that is, higher concentrations of malic acid, yeast-assimilable nitrogen and glutathione.

Delaying the date of the first hedge-trimming (or ‘tip-pruning’) is of limited technical value in vineyard canopy management. The impact of the delay on lateral shoot growth and must composition remains marginal within the context of the La Côte vineyard in Switzerland.

The effectiveness of an application of foliar nitrogen at veraison depends on the initial level of vine nitrogen deficiency, an Agroscope study has shown. The threshold levels of assimilable nitrogen deficiency in the grape must are validated for Chardonnay but still need to be confirmed for Sauvignon Blanc.

Grapevine leaf removal (LR) in the cluster area is a common practice in temperate and cool climates, usually done between berry-set and cluster closure to create a less favourable microclimate for fungal diseases and to improve grape ripening. When applied before flowering, LR affects berry-set and is, therefore, an effective yield-control tool, reducing time-consuming manual cluster thinning; it also improves berry structure and composition (i.e., total soluble sugars [TSS], titratable acidity [TA] and polyphenols) (VanderWeide et al., 2021). The present five-year trial follows a previous study about pre-flowering LR under identical environmental conditions (Verdenal et al., 2019); it validates the sustainability of moderate pre-flowering LR and its possible mechanisation under Swiss climatic conditions, using low-pressure double airflow.

Knowledge of the nitrogen nutrition status of the vine is essential for long-term management of its nutrition with the aim of producing high-quality grapes. Measurement of the chlorophyll index is a fast, non-destructive and relatively inexpensive method that provides a good approximation of the nitrogen nutrition status of the vine during the growing season. Several chlorophyll meters are available on the market, each using its own measurement unit. With the aim of popularizing the use of chlorophyll meters, the interpretation thresholds of the SPAD index, measured on the vine at the veraison stage, have been established from correlation with the N-tester index, for which the thresholds are already known.

La teneur en azote du moût à la vendange joue un rôle déterminant dans la cinétique de fermentation alcoolique et dans la formation des arômes du vin, particulièrement dans le cas des vins blancs. Au cours des dernières décennies, les pratiques viticoles ont considérablement évolué vers moins d’herbicides et davantage d’enherbement. Dans ce contexte, des carences azotées du moût sont apparues de façon récurrente dans certains vignobles. Comment pouvons-nous adapter nos pratiques culturales à ce contexte de concurrence pour l’azote ?

Defoliation of the vines consists of eliminating the leaves in the grape bunch zone in a more or less intensive manner. It is a long-proven prophylactic technique that has seen a renewed interest in the current context of the reduction of phytosanitary inputs. However, several questions remain. Which is the optimal period? What is the ideal intensity? What are the risks? Is the mechanization of this process a feasible option? Agroscope has been undertaking defoliation trials in Switzerland since 2010 in order to shed light on these questions.