All grapevines need water to survive. If it doesn’t come as rainfall during the growing season as in Bordeaux and Burgundy, it must be added via irrigation as in California. The exception is old vines whose roots get their water from deep in the subsoil. Oregon receives summer rain but still needs irrigation to survive heat spells. Nonetheless, irrigation conjures up images of overcropping. Since these images do not sell wine, they are seldom discussed. Non-irrigation or dry-farming evokes images of stressed vines and low yields which are perpetuated in the wine press because they do sell wine.
Andy Humphrey points out the trend toward irrigation in Oregon for producers who can afford it: “Everything in Oregon until recently has been dry-farmed. It’s the new people coming into Oregon—King Estate, Gary Andrus—and planting new ground on tight spacing that introduced irrigation and it’s catching on. The irrigation systems are there to establish the plant and if you need it later, it’s there.” Successful plant establishment is a big economic concern because the grafted plants, at $3 a piece, are five times the cost and considerably more fragile than their own-rooted predecessors. Humphrey adds, “We’re planting 2,000-4,000 per acre and we don’t want to lose them.” Humphrey explains the importance of irrigation aside from plant establishment, “In Oregon we get a heat spell every August or September. In 1994, it occurred just as the grapes were reaching maturity. The numbers (sugar, acid, pH) were all looking right but the flavors had not really developed. The acids were dropping, the sugars were shooting up, the fruit was starting to shrivel and everyone was panicking and picking as fast as they could. We knew the flavors weren’t there so we turned on the irrigation and gave the plants a blast of water which prevented the grapes from dehydrating and shriveling. The brix went down because we hydrated the fruit but then we turned it off and let the grapes hang on the vine for another two weeks. The flavors developed, the sugar and acid numbers were all right and it was wonderful wine.”
The Late Justin Meyer discussed the potential drawbacks of dry farming, “On the whole West side of Napa Valley (west of Highway 29) it is very hard to find wells. As a result, many of those vineyards are dry-farmed—surviving on the 35” of rain in an average year. In a year like that, you don’t need supplemental moisture. But in a drought year like ‘76 &’77, those vines not only suffered in quality but their quantity was way down because they just ran out of moisture and shriveled up. Maybe they got half a crop of not very good quality because the grapes tended to be raisiny. In a situation like that, you wish you had water. When people say that irrigation is bad for quality, you can be sure of one thing, they don’t have irrigation.” But Meyer acknowledged that you can over-irrigate, “If the growth never slows down because you have too much water then the fruit probably won’t get very ripe. You have got this competition between vegetative growth and fruit maturity and at some point you have to bring the vegetative growth under some kind of stress by not irrigating so that vine will slow down or stop its growth and ripen the fruit.”
Lemon explains where irrigation is crucial, “Stress due to a lack of water—dehydration—is not a positive; the vine needs to get enough moisture. I work with a property on Diamond Mountain with a dry, volcanic tuffa, a soil low in nutrients and organic matter. If you let that stuff get stressed out due to lack of water, the vine will just give up on you—it will start to drop its leaves and the fruit will shrivel up. We have improved wine quality on that property by making sure that those vines do have sufficient irrigation to make sure that they don’t stress, don’t shut down and don’t ripen too quickly—to prevent the wrong kind of stress. We saw that in the ‘76 Burgundies—a drought year—the Cote de Beaune didn’t make as good wine as the Cote de Nuits which got a little more rain. We are still trying to understand it and nobody has the answer as to when and how much water deficit is appropriate.”
The question of yield is ever-present in discussions of wine quality. And why not, excessive yields have so often been the culprit in the production of poor wine. But by focusing on yield to explain the elusive question of wine quality, two problems arise: (1) In California, higher density vineyards are making the traditional yardstick of yield–tons/acre—obsolete. And in older vineyards in Bordeaux and Burgundy non-productive or missing vines make claims of low yields misleading. (2) The focus on yield as the limiting factor in wine quality, draws attention away from other factors without which it is impossible to produce great wine. Pontallier underscores perhaps the most important factor: “The difference in quality between the first growth Chateaux and the second growth Chateaux is a fact which has been consistently recorded over the last three centuries. Between these Chateaux, yields are about the same and so is the technology of production. The only true difference is the site, the terroir, whose composition is not a mystery anymore but whose influence on the quality of the wine remains difficult to understand.” The question of quality is no easier to assess. In evaluating wine quality, what role do perceptions play—of limited production, marketing, a charismatic winemaker and numerical ratings—in what is ultimately an emotional, aesthetic and therefore subjective judgement?
—Jordan Ross, Practical Winery & Vineyard 1999–2000