We managed two of the vineyards mentioned in the article. Both Bieze and Nysa….
We managed two of the vineyards mentioned in the article. Both Bieze and Nysa….
Last week, the Oregon Wine Symposium was held in Portland Oregon at the Oregon Convention Center. Vitis Terra Vineyard Services had a trade show booth at the symposium for the first time. In addition Chemeketa Community College also had a booth and a large number of students attended event. It was fun to see everyone at the event and luckily I did manage to go to several talks that were quite interesting.
I attended the “Ebb & Flow: The Dynamics of Water Availability and Vine Use” by the new Oregon State University Southern Oregon researcher Dr. Vinay Pagay. We had just covered water relations in my Vine Physiology class at Chemeketa so it was a nice review.
He discussed the grapevine growth cycle and talked about the impact of the previous season and the water status on the development of the compound bud that will produce the following season’s crop. He also discussed the grapevine water potential that involves the soil plant atmosphere continuum and is driven by transpiration.
He reviewed what controls the negative water potential gradient which includes a number of variables such as environmental conditions, soil characteristics, soil moisture and resistances in the plant. Two of the main factors driving water use are canopy size and evapotranspiration. These are two factors used in calculating the amount of water to irrigate with on a weekly basis. In grapevines the greatest resistance or control of water loss is through the stomata on the undersides of the leaves. If these close in response to drought stress it will also slow down photosynthesis and grape ripening.
While excessive water can lead to high vigor, he also discussed the negative impacts drought stress can have on fruit quality such as the loss of the aromatics in white wines and stressed vine off aromas in red wines. In Oregon we often have too much vigor early in the spring due to our rainfall and then late in the summer and fall many vineyards have high levels of drought stress. We could improve our fruit and wine quality by understanding and managing irrigation better. Growers and winemakers get concerned about using irrigation between veraison and harvest but this is the time that it can have the greatest impact on wine quality.
He mentioned that a grapevine typically uses 1000 gallons of water per vine per season. During the summer in our cool climate a grapevine can typically use 8 gallons per day. I think it is very important to keep this in mind because when we do provide irrigation, it is a very small amount compared to the total number of gallons used in a year or even a given week! If you do a 3 to 5 gallon irrigation set you are lucky if you’re replacing 50% of the water used that week.
As far as when irrigation has the greatest impact on berry size, the greatest impact is from bloom through fruitset as this is when cell division is occurring. Before veraison water moves into the berries through the xylem. Consequently there can be a greater impact on berry size related to water status before veraison. After version the xylem becomes nonfunctional for water moving into the berries, however; the most recent research suggests there could be xylem back flow of water out of the berry.
At veraison, water and sugar move into the berry through the phloem. When this occurs, the berry becomes more isolated from the vine. Keller’s research shows that at this point irrigation can help prevent shrivel but once shrivel has occurred it can’t be used to reverse the shrivel but only to prevent more shrivel.
Another talk at the symposium, “Water into Wine: The Downstream Effects of Vineyard Water Management on Wine Quality” presented some interesting information on the changing water content in berries due to rain events. This relates to what we experienced during harvest in 2013. Watch for the next blog on this topic.
Markus Keller, Jason P. Smith and Bhaskar R. Bondada. Ripening grape berries remain hydraulically connected to the shoot. Journal of Experimental Botany, Vol. 57, No. 11, pp. 2577–2587, 2006.
One day we are thinking about the risk of an early budbreak and now today I am happy the grapevine buds are safe and protected as the temperatures dip down into the teens. If the warm days have caused them to start deacclimating, they would be at greater risk of cold injury. Luckily, at least this week, the weather will keep them in a dormant state; cozy inside their protective bracts and hairs.
These compound buds are extremely important as they will produce the shoots that support and ripen the clusters in the coming vintage. If these buds are damaged, it can result in a loss of shoots and or crop.
At this time of year, the buds appear brown with occasional tufts of white epidermal hairs showing. As they go into dormancy, they lose water and become lignified. When they obtain maximum cold hardiness, the buds can resist temperatures down to around -8 to -10 degrees F.
The compound bud on a grapevine is a truly amazing work of biology. The compound bud really contains three buds (primary, secondary and tertiary) so this in itself increases the chance of survival for the vine. Within the primary bud, there are a number of primordia (growing points) protected inside. The compound bud can contain 6-10 leaf, 1-4 cluster, one lateral and several tendril primordia all compressed into this small inconspicuous bud. It is somewhat like an accordion.
In the spring the buds go from being in a dormant cold hardy state to active growth at which point all cold hardiness vanishes. Spring shoot growth bursts from these buds supported by carbohydrates and nutrients stored in the trunk and roots. The leaf primordia inside accounts for about two thirds of the total shoot grown that occurs by bloom. As they grow, it is like opening the accordion and creating space between each node that will contain a specific pattern of leaves, clusters and tendrils.
Spring will happen all too soon so for now I am happy to stay warm inside and enjoy the snow.
Wow! What a beautiful day! I got up early as I teach my Chemeketa Community College Winter Vineyard Practices lab on Saturdays. With a venti cappuccino in hand, we were ready to do some pruning. The students practiced choosing the best fruiting canes and also looked for good positions for pruning the next year. The sunny weather was so nice, everyone wanted to keep pruning……
On Thursday, one of my students brought a cane over to me and said, “Look at this!”. I was in a bit 0f denial as I said….. “What?”. The fuzzy buds! Yikes! This warm weather is likely to start causing bud swell and could promote an early budbreak. If we have an early budbreak this also increase the risk of frost. My action plan is to pick up the pace on getting the vineyards pruned and new canes tied down.
I actually bought the Statesman Journal newspaper yesterday as the front cover article was titled, “Winter drought sparks concerns across the state”. How often is it so dry in western Oregon in January that we have forest fires and the National Weather Service issues a Fire Weather Watch alert! Yes, highly unusual.
There is some rain in the forecast in the coming weeks but it looks to be rather minimal at best. Meanwhile, my action plan is to prune faster, burn my burn piles and get the layout done at my house so I can get my vines planted sooner rather than later.
As I sit here drinking my coffee and looking out at the fog, I am pondering the fact that everything looks wet and gloomy out there but really we might be headed for a drought if weather patterns don’t change soon. Well. maybe I will get lucky and the sun will come out up here in the Eola-Amity Hills!
However, the fog versus sun doesn’t change the fact that right now we are headed toward drought across much of the Pacific Northwest, California and the Southwest if we don’t move out of this powerful, persistent ridge of upper-level high pressure has prevailed off the U.S. West Coast for more than a year now. This pattern—the strongest and longest-lasting of its type in decades, according to meteorologist/blogger Daniel Swain.
California declared the state in a drought emergency on January 17th. California has broken rainfall records going back to 1849 in the San Francisco area. Oregon has yet to declare a drought although this could happen soon if we don’t receive more rain in the rest of the water year.
For clarity, it is important to understand the difference between discussions on the water year versus the calendar year. The water year runs from October to October. We are in effect about half way through the water year even though we are only about 1 month into 2014. While we had a record 6 inches of rain or so in September during the winegrape harvest, this was part of last year’s water year.
At the Aurora Agrimet agricultural weather network, it shows only 6.49 inches or rain in the water year to date while the average is 25.23 through January. The next couple weeks look like we will stay in this high pressure ridge as described in the Fox 12 Weather Blog. The question is will we move out of this high pressure ridge quick enough or are we likely to end up in drought conditions.
In comparing water year data to date from the Aurora Agrimet going back 10 years, the closest year in dryness was 2004-05 where there were 13.38 inches of rain. This is still double where were are now. In 2004-05, by June the valley had received around 30 inches of rain. We will need to have a wet spring to make to fill the soil profile with moisture prior to budbreak. In my memory, it does seem that we often have a wet late spring following a dry winter but we are in a serious deficit right now so we will have to keep a close eye on precipitation the next few months.
What does this mean for the next couple weeks; great weather to get your winter pruning done in the vineyards while it is not raining but there is plenty of humidity from the fog to tie the fruiting canes down without breaking them.