Grapevine shoot development as a function of arm positioning
Variability is one of the key issues discussed at the Napa Vintage Report conference this year. According to Dr. Peterson of Cal Poly San Luis Obispo, while variability can add complexity and contribute to many desirable wine characteristics, it becomes an issue if it impacts the economic viability and ability to manage the vineyard in a cohesive and time-effective way.
Dr. Peterson’s talk at the Vintage Report touched on an interesting variability in the vineyard associated with arm positioning along the cordon. On the same spur-pruned cordon, different arm positions may exhibit variable characteristics and develop at different rates.
This is not usually a problem at the beginning of the life of a vineyard. However, Dr. Peterson emphasized the importance of catching this variability early on and on a yearly basis to continually improve the fruit and wine quality.
Several variability issues we can observe along the cordon include the following:
- Delay in bud break
- Variation in timing of bloom
- Stunted and weaker shoot growth
- Variation in the timing of fruit maturity
- Discrepancy in fruit composition and quality at harvest
How should vineyard managers deal with the variability along the cordon with regard to shoot positioning in order to normalize the growth rates?
The study analyzed three different pruning methods (5.5 shoots per meter, 11.1 shoot per meter, and 11.1 shoots per meter with leaf removal) and their impact on final pruning weights, cluster weights, shoot lengths, and spur diameter. The goal of the last treatment is to tease apart the effect of light penetration from the number of shoots. The experiment was done in a 16-year-old Cabernet Sauvignon vineyard at the UC Davis Oakville Station.
The study revealed that overall, shoots positioned at the end of an arm were stronger than shoots near the mid and trunk sections of the cordon. Additionally, reducing the shoots per meter homogenized the shoots along the cordon according to shoot lengths and pruning weights.
Understanding how pruning strategies and changing number of shoots per meter affect homogeneity in the vineyard allows vine growers to make quick vineyard changes from one year to the next. This will be key to align vine health and sustainability during a changing climate.
Fruition Sciences offers a full suite of products addressing a variety of vineyard needs to enhance fruit and wine quality. Physiocap helps vine growers understand the variability in dry biomass accumulation in your vineyards to optimize pruning strategies.