Justine Vanden Heuvel
Associate Professor, School of Integrative Plant Science, Cornell University
What is Vine Balance?
Vine balance is the ratio between vine size (vegetative growth) and vine yield (fruit growth). It can also be described as the ratio of carbon supply to carbon demand. Vine organs that produce carbon through photosynthesis or reallocation from storage are called “sources” while organs that import carbon are called “sinks”.
The concept of vine balance was first developed in the early 1900’s but further refined by Professor Nelson Shaulis at Cornell University in the 1950’s and 1960’s. Shaulis developed balanced pruning formulas that adjusted node number based on pruning weight from the previous season.
Metrics for Vine Balance
Many metrics are used to express the balance of vegetative to reproductive growth, including:
- Ravaz index (yield divided by the pruning weight of the same season)
- Growth-Yield relationship (yield divided by the pruning weight of the previous dormant season)
- Leaf area to fruit ratio
- Pruning weight per vine or linear length of row
- Individual cane weight
Key Concepts
- Source-sink balance impacts allocation of dry weight among vine organs.
- Photosynthesis and utilization of carbohydrates are tightly linked. When sink activity is decreased, carbohydrates accumulate in leaves and photosynthesis is inhibited. Increased sink demand can enhance photosynthetic activity.
- When fewer leaves are present on a shoot, the shoot tip becomes an even stronger sink for carbon than the cluster. When carbon is limited, the vine reprioritizes it’s sinks to ensure vegetative growth.
- In cool climates, increased yield does not necessarily reduce vegetative growth of the vine if there is no stress (ex. Drought, disease, etc.). In warm climates where water is limited, vegetative growth is usually diminished when yield is increased.
- Vine balance has a significant impact on fruit composition, but the relationships are not well understood. The impact of vine balance on fruit composition deserves more research to further fine tune wine composition.
For More Information:
Publications:
Howell, G.S., 2001. Sustainable grape productivity and the growth-yield relationship: A review. Am. J. Enol. Vitic. 52: 165-174.
Kliewer, W.M. and N.K. Dokoozlian, 2005. Leaf area/crop weight ratios of grapevines: Influence on fruit composition and wine quality. Am. J. Enol. Vitic. 56: 170-181.
Lakso, A.N. 2013. Untangling the concepts of vine size, capacity, crop level, vigor, and vine balance. Appellation Cornell Issue 13.