Preparing for a Wet Winter

El Niño conditions are setting up that could mean dealing with excessive rainfall in California after three consecutive dry years
Dec 4, 2009

Across most parts of Santa Barbara County, there has not been any rain since the solitary and very early downpour in the middle of October that dropped almost 3 inches of rain. Since then, other than the occasional heavy fog, we've had no precipitation in our area. Except on the north-facing and on some west-facing slopes, the early grass has withered and died.

This is the time of year that we turn the bulls loose with the cows. With the poor feed in the hills, there are not enough nutrients available in the pastures for the cows to cycle properly for breeding, nor for them to produce adequate milk for the two- to three-month-old calves at their side. I am feeding the cattle oat hay and alfalfa every day.

However, the weather forecast indicates that next week will be wet. It appears that from Monday onward the jet stream will be over Central California and throwing lots of wet stuff in our direction. Let's hope it doesn't come all at once. Based on warming temperatures in the equatorial Pacific Ocean, the winter forecast is for an El Niño condition. This typically translates into less rainfall in the Pacific Northwest and more rainfall further south over California.

After three very dry years in a row (that were very good for wine quality), we could use a wet winter to help flush the accumulated salts in the upper soil boundaries. Viticulture in low-rainfall regions is a double-edged sword, in that we enjoy the positive contribution to wine quality that low rainfall gives us, but at the same time, it can adversely affect soil conditions in the long term by increasing salts.

In looking at the most important positive contribution, low rainfall is what allows us to practice deficit irrigation. In California, deficit irrigation is an important tool in managing vine vigor to improve wine quality. It is the ability to use controlled deficit irrigation, more than anything else, which distinguishes the wines of California.

Many people have heard the adage that "the dying vine makes the best wine." The lesson taken from this metaphor is the basis for many modern viticultural practices such as deficit irrigation and canopy management.

It is not that "the dying vine" makes the best wine because it is dying. It is the physical characteristics of a low-vigor vine with limited leaves, and with fruit that is somewhat exposed to sunlight, that improves wine quality.

Modernly the historic observations of "the dying vine" are implemented through controlled deficit irrigation to prevent excess vigor and shading in the canopies. One interesting aspect is that, by controlling available water, we are able to control berry size. By decreasing berry size, the ratio of skin to pulp is increased. If you remember from geometry, as the size of a sphere decreases, the relative ratio of surface area (skin) to volume (pulp) increases, with important implications for the wine's attributes.

Additional techniques learned from "the dying vine" are the use of leaf pulling and shoot thinning. If implemented appropriately, these practices lead to increased color and improved flavors in wine. Sunlight tends to decrease herbaceous characteristics in the fruit and actually converts the compounds responsible for green flavors (pyrazines) into terpenes, which are floral and fruity in character. The increased ability of air and sunlight to enter the canopies also results in lower fungal disease pressure and the use of less sulfur.

It has been apparent for several months that an El Niño condition was setting up for the winter. In my next blog I will detail some of my strategies for dealing with the increased rainfall so that when the vines are growing, I will still be able to use controlled water deficit to manage their vigor even next spring and summer.

I hope some of the readers are able to visit Santa Barbara County for this weekend's "Holiday Weekend in Wine Country." If not, consider that tomorrow, Dec. 5, is the 76th anniversary of the repeal of Prohibition. If you find yourself with family or friends enjoying a bottle of wine and feel so inclined, remember to be safe and to toast the end of Prohibition!

Harvest United States California Santa Barbara County 2009

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