Leaving more growing nodes per vine at pruning (to increase vine productivity) and applying deficit irrigation strategies (to increase fruit and wine quality) are are widely used practices, particularly in high yielding vineyards under warm climate. However one may ask how those practices impact vineyard longevity and sustainability ? To better understand the impact of such practices, a team of researchers led by Pellegrino in 2014, conducted a study in a warm irrigated region. Researchers specifically investigated how those practices could impact a) carbohydrate dynamics in vegetative organs, b) plant capacity to maintain productivity and ripen fruits. Among many results, authors found that:
- Trunk carbohydrate concentrations markedly varied between seasons, highlighting the importance of interactive factors such as crop load and climate on carbon status. (For instance, high temperature or high vapor pressure deficit affect canopy’s ability to produce carbohydrate).
- Total carbohydrate pool (starch and soluble sugars) at the end of dormancy increased under lighter pruning, due to higher vine size, and greater retention of old-wood (trunk and cordons)
- Water deficit negatively impacted trunk starch concentrations in Cabernet Sauvignon. The lower trunk starch concentration under water deficit resulted in a decrease of yield components at harvest. The lowest concentrations of stored carbohydrates in trunks occurred between fruit set and véraison period, indicating that this period is critical for carbon balance. (Figure 1)
Figure 1: Water deficit (Low irrigation) decreased starch concentration (adapted from Pellegrino et al, 2014)
- Reassess at the end of each season how climate and practices have affected your vine ability to restore and maintain its pool of carbohydrate (Physiocap)
- Monitor carefully water deficit during the period fruit set to veraison to optimize quality and quantity. If you are managing high yielding vineyard, managing water deficit too severely may result in lower starch concentration in vegetative organs, which will reduce yield. (Sap flow)
- Even if vine yield and carbohydrate status in vegetative organs varied widely between seasons, sugar allocated to berries at harvest remained remarkably stable.
In conclusion, under warm climate, vintage variations result from a combination of high climatic demand and human practices such as deficit irrigation and varying crop load. The mix of such factors will affect vineyard performance and create year to year variations. Through the monitoring of vine reserves variations you can follow the resulting effect of your farming strategy on vineyard production sustainability.
Check out our article about Rotundone mapping for more Physiocap application