Dry farming is a method that takes advantage of the water naturally available in the soil. When strictly applied, it excludes all forms of irrigation during the productive period of a vineyard.
According to Tod Mostero, viticulturist at Dominus Estate in California’s Napa Valley, dry farming forces the vine’s roots to plunge deep to explore greater volumes of soil and areas that are naturally moist.
“Because grapevines are capable of flourishing in this environment without depleting natural resources or the soil’s nutrients, we believe that dry farming grapevines is the best way to preserve the integrity of the site,” Mostero said.
Dry farming is one way of conserving water in drought-stricken California. According to the U.S. Geological Survey, California is entering a sixth year of drought.
According to Dave Runsten, policy director for the Community Alliance with Family Farmers (CAFF), some winegrowers are hesitant to dry farm since the practice generates lower grape yields. However, he added, winemakers can price their products accordingly to compensate for the difference.
For the past several years, Runsten said, CAFF has held dry farming workshops across California as part of an outreach effort.
According to treehugger.com, dry farming in Napa Valley requires 16 to 20 inches of annual rainfall in order for the vines to sustain the region's hotter months, May to October. Napa receives about 36 inches of rain annually.
Frog’s Leap Winery in Napa Valley has been a trailblazer in the dry farming movement.
For about 125 years, all wines in Napa Valley were dry-farmed, according to Jonah Beer, general manager and vice president of operations at Frog’s Leap Winery.
The winery, which is one of the first organic certified vineyards, started dry farming in mid-1980s. Beer estimated that dry farming saves about 40 Olympic-sized swimming pools of water each year.
While water conservation may be a benefit of dry farming, it is not the only impetus. Beer said that dry farming produces a more flavorful and nuanced wine that is intrinsically linked to its terroir--the complete natural environment in which a particular wine is produced.
“When we dry-farm our wines, we actually get better wine,” he said.
Since the roots of dry-farmed grapes go about 30 feet into the ground, Beer said, the plants acquire flavors that are naturally present in the soil.
The extremely deep roots make them robust and more resistant to diseases.
In comparison, he said, irrigated grapes sit on the vine much longer and end up with an extremely high sugar content, which translates to a high alcohol content. As the alcohol content in wine increases, acidity decreases and has to be added in later.
Those factors, Beer said, make irrigated wines lack the distinct flavors of dry-farmed wines.
“Dry farming reveals and highlights those flavors because there’s nothing to stand between the connection between the roots and the soil,” he said. “It tends to affect the wines in a very subtle and layered way.”
Adam Fox, co-owner of Canard Winery in Napa Valley, said that Canard took up dry farming primarily because it enhances the flavor of wine.
“It has a flavor profile that’s more terroir-driven, more distinctive,” Fox said.
The improvements in quality come at a price. While vineyards that irrigate yield 8-10 tons of grapes a year, he said, “we bring in 3 to 4 tons on a good year.”
“You sacrifice a lot of yield for this process,” Fox said. “We made a philosophical decision years ago to produce a smaller amount of great wine.”