The Importance of Pre-Bloom Ca, B and Zn in Table & Wine Grapes
We’ve been told for years about the importance of including Zinc (Zn) in our pre-bloom foliar nutritional sprays. And now we almost universally include Zn without even thinking about it.
Because adding Zn has almost become automatic, I’d like to highlight the “why” behind pre-bloom Zn. I’ll also address the critical role Calcium (Ca) and Boron (B) play (in conjunction with Zn) in pre-bloom nutrition. Here’s a quick synopsis of what each element does for the plant and why it’s a necessary component in pre-bloom nutrition.
- Calcium (Ca): The key component in cell walls, maintaining membrane structure. Ca has a direct influence on the regulation of enzyme systems, phyto-hormone activities and nutritional uptake. It has a specific influence on fruit quality, color and aroma. Low Ca concentrations in fruit lead to earlier maturity and softer skins. This correlates directly to fruit quality in table, raisin and wine grapes. Nearly 40% of a vine’s Ca absorption takes place between leaf emergence and fruit set.
- Boron (B): Is involved in various enzyme systems and carbohydrate metabolism. B also plays a critical role in pollen tube formation and fruit set. Low B concentrations can lead to shot berry, uneven ripening and, in the case of wine grapes, seedless berries. Due to its high solubility, foliar applications of B are very effective in correcting deficiencies. Typically, 90% of applied B is taken up by the plant within 24 hours. Pre-bloom foliar applications are the best way to ensure pollination, helping to avoid fruit set problems.
- Zinc (Zn): A key component in the development and function of growth regulators (i.e. auxins) that influence internode elongation, rachis stretch and bunch formation. Deficiencies can lead to poor fruit set, stunted shoots and loose clusters with undersized, irregularly shaped fruit that ripens unevenly.
Before you think about making a nutrient application, it’s always important to know the nutritional history and get a current tissue analysis to determine the rate and type of nutrient needed. Once you’ve determined need, the two final critical factors are “when and with what.”
The” when” is simple--the earlier the better. If you can get your pre-bloom application on just as the infant cluster is emerging from the shoot, you will ensure the nutrients have time to absorb and translocate to the structures as they are forming.
Including Megafol® and eXploit® in your spray will help kick-start the vines’ metabolism, which helps drive nutrients to the fruiting structures. I like to see a minimum of 2 pre-bloom (cluster emergence & 7 days pre-bloom) foliar nutrient applications in varieties that don’t have historical set issues and 3 applications (cluster emergence, 7 days pre-bloom, & bloom) to varieties that struggle with set, cluster development and berry formation. These would all be tank mixed with powdery mildew applications.
A simple, easy and very effective pre-bloom program consists of Ele-Max® CalBor Zn FL + eXploit + Megafol. You get a great ratio of Ca (15%), B (3%), Zn (6%) and N (4%) with the CalBor Zn FL plus the metabolic benefits of Megafol and eXploit working together to maximize nutrient uptake. If B is adequate, another great option is tank mixing Brexil® Zn (10%) + Brexil Ca (15%) + eXploit + Megafol. The Brexil Ca has a very small amount of B (0.5%), but not enough to influence tissue levels.
The bottom line: We have a great number of tools available to help growers maximize yield and quality. The key is timing, rates and superior inputs.
- Paul Crout PCA/CCA, Product Manager, Coastal