Global warming increases spring-frost-related damages and accelerates grape ripening depicting a dramatic scenario in sparkling wine regions. Several European vineyards recently have experienced higher frequency of spring frost inducing growers to adopt uncommon anti-frost actions. Late winter pruning (LWP) was recently proposed as a relatively cheap technique allowing to significantly post-pone grapevine budburst and, eventually, fruit ripening. However, the higher the delay in canopy regrowth in spring, the lower the yield at harvest suggesting that a finer tuning of technical and physiological interactions is still required before upscaling. A condition that is especially urgent in sparkling wine districts of North of Italy where LWP is almost unknown.
A 2-year trial (2020-2021) was performed in Chardonnay vineyard by comparing standard, late (LWP), and very late cane winter pruning (VLWP). Treatments were applied when shoots at top of unpruned canopies developed 1-3 (LWP) and 3-5 (VLWP) unfolded leaves; the leaf area removed from LWP and VLWP vines was 0.40 and 0.89m2 (2020) and 0.04 and 0.08m2 (2021), respectively. Phenology and ripening kinetics were monitored, and yield components and must composition determined either on a per-vine and on a per-shoot basis. LWP and VLWP postponed harvest (must pH=3) by 20 and 23days (d) in 2020, whereas a milder effect was recorded in 2021 (8d in both treatments). Treatments curtailed yield per vine by 69 and 79% (2020) and by 11 and 20% (2021), respectively; regardless of seasonal variability and timing of pruning, yield limitation increased from distal to basal shoots depending on reduced fruitfulness. Data showed negative correlations between removed leaf area in spring, vs. yield (R2=0.85) and TSS concentration (R2=0.70) at harvest. Results allow a more accurate identification of the pruning time x removed leaf area combination which might reconcile consistent delayed phenology and limited yield decrease in cane-pruned Chardonnay grapevines.
Authors: Alessandra Garavani, Alberto Vercesi, Tommaso Frioni, Stefano Poni and Matteo Gatti
Department of Sustainable Crop Production, Università Cattolica del Sacro Cuore, Piacenza, Italy
Keywords: climate change, yield, source-sink balance, sparkling wine, vineyard management