November 2007 Issue of Wines & Vines
Dry, Dry Again
Why a few California growers say no to irrigation
Spring fog swaddles dry farmed Chardonnay vines at Kunde Estate Winery & Vineyard in the Sonoma Valley. Vine rows are tilled to prevent cover crops from competing for water and nutrients.
"You can put whatever spin you want on it," John Williams, owner of Frog's Leap Winery in Napa Valley, said. "But I'm dry farming because of the results I can see in the wine." That feeling was echoed by others, along with sharp concerns about dwindling water supplies and other conservation issues.
Other growers and winemakers, who don't believe they can dry farm on their sites, for whatever reasons, are moving to reduce water use through deficit irrigation and other techniques. (See Off-Dry Farming.)
All of Napa was dry farmed until the 1960s when overhead irrigation was introduced, although overhead was primarily a frost control device. A primitive form of drip irrigation was first seen in the early 1970s, but prior to that, the vines got whatever nature delivered. So, as Williams points out, the wines that formed the classic Napa Cabernets--Inglenook, Beaulieu, Louis Martini and a handful of others--were from dry farmed vineyards.
"What have we lost?" Williams asked during an interview, clearly not expecting an answer. But whatever might have been lost over the last three or four decades, Williams is determined to find out. He is now farming 200 acres of Napa vineyards in the Rutherford AVA, without irrigating.
Williams was careful to point out that he is not talking about walking out one morning and turning off the taps. Dry farming is part of a total holistic system of farming. In his view, proper tillage is at the heart of dry farming.
"By tilling, you form a dust mulch that seals the water into the ground, and the only way it can get out is by capillary action through the vine's roots. The dirt actually becomes a sponge, holding the moisture, which is released slowly through the vine," he said. Williams said his vineyards are tilled about every 10 days to varying depths, creating the thick mulch that is essential in dry farming.
You can walk the vines with Williams and see and feel the difference in the soils between his vineyard and a vineyard only a few yards away that is drip irrigated. Walking between the rows, your shoes sink deep in the soil--it does, in fact, feel like walking on a sponge. It is easy to sink a shovel into the soil to a depth of 8 to 10 inches, barely pushing the handle. The soil is dark and moist, even though it had been more than two weeks since any significant rainfall at the time of our visit. Walking across a narrow vineyard lane, the soil is hard and dense. It requires a major effort to push a shovel even a few inches into the soil, which is dry and crumbly, with little capacity to retain moisture.
"Conventional growers will tell you that cultivation compacts the ground and uses unsustainable amounts of fuel. This just doesn't measure against real experience. Good growers know when it is time to stay off from wet vineyards and when it is time to work them. The amount of fuel used pales in comparison to the spray and irrigate alternative," Williams said.
Rootstock selection is part of his dry farming package. "AXR, for example, is from riparia-based rootstocks that have shallow spreading roots. Drip causes the roots to stay shallow, rather than dig deep into the soil for moisture and nutrients. If you want to dry farm, you should use rupestris stock, like St. George. The ancestors of rupestris were from dry country; the roots go deep. But in a drip situation, even St. George roots stay on the surface. They learn that's where the water is," Williams said. He believes that it was the shallow rooting that gave phylloxera a second shot at Napa vineyards, since it is easier for the louse to get to the roots.
Looking to the past
Williams also looks to the past in planting a new vineyard, which he prefers to do rather than try to convert existing drip irrigated vines to dry farming. Rather than the common practice of bench grafting, Williams field grafts the young vines, giving the rootstock a head start. "I want to see vigorous growth above the ground, because I know there will be equal below-ground root growth."
If a new rootstock seems to be struggling, a hole at least 2 feet deep is dug beside the plant, and 5 gallons of water poured in. The hole is then covered. "I don't want to put the water on the surface for the young roots. I want them to learn to go deep for moisture." If the rootstock is healthy, it is grafted the year following planting.
At Frog's Leap Winery in Napa Valley, some 200 acres of dry farmed vineyards are tilled every 10 days to create a thick dust mulch that seals moisture in just below the surface.
He added, "If we talk about when wine went from its historic place as a mealtime beverage that deeply reflects the soil and climate from whence it comes to killer, jammy monsters that advertise that they will 'melt your panties,' I think you will come to the same conclusion that we did 18 years ago: that the real wines are made by deeply connecting them to their soils and that dry farming is fundamental to that."
On a more bottom line issue, Williams said that barring a severe drought, there is no problem of lower yield for dry farming if you are shooting for quality in the first place.
"The old-timers figured that it took about 18 inches of rain a year to keep a grapevine healthy. If you fall below that, you might start losing tonnage. What does happen is that we thin less. If the vines were setting a crop of 10 tons, we would thin to 4 tons. So they set a crop of 5 tons and we thin to 4. It makes more sense," Williams said.
Converting a vineyard
Williams likes to start with new vineyards for dry farming, but it is possible to convert an existing drip vineyard. Jean-Pierre Wolff, owner of Wolff Vineyards in Edna Valley on the Central Coast, successfully converted a 45-acre Chardonnay vineyard from drip to dry farming in 2000.
Wolff said he used the technique of deep ripping the ground up to 10 feet deep with a pre-shank hook to help wean the vines from drip. "The idea is to give a haircut to the shallow roots so the taproots go deeper," he said. He also added 1.5 tons per acre of gypsum soil amendment, as gypsum helps improve water percolation.
If rain is forecast, Wolff builds a system of zig-zag culverts to hold the rain and slow runoff, creating small holding ponds with a series of little levees. The standing water then goes into the ground, building up groundwater under the vineyard.
There has been no decline in crop size since the change to dry farming was made. "I drop fruit to about 3.5 tons per acre. I would do that anyway," Wolff said.
Asked why he had made the change, Wolff said that he was convinced that it would improve wine quality after tasting wines from old vine, dry farmed vineyards. "The wine that is dry farmed is better, it has more complexity. It has been well received by consumers. I sell fruit to other wineries. They are happy with it."
Dry farming of winegrapes isn't limited to California. Dry farming is virtually a given in much of Europe, although there are also more frequent summer rains, especially in France and Germany. However, parts of Spain such as the Priorat have been traditionally dry farmed, even though summer rainfall is rare.
Even in Australia, where irrigation is the norm, there is interest in dry farming, especially in the wake of what Australians are calling a "thousand-year drought." Graham Due, an Australian vine researcher who owns GroGuard, a manufacturer of grow tubes, says that in drought situations, vines that are dry farmed come through better than irrigated vines.
Before thinking of dry farming, Due said via e-mail that it is essential to consult a soil scientist. "The right soil is absolutely crucial. I would not proceed without the assistance of a soil scientist who fully understands the issues, or a history of successful un-irrigated viticulture on the site." He added to especially beware of soil that is easily penetrable over a layer that is impenetrable to root growth and water movement "In these soils, the vine grows like crazy early in the season and exhausts all available water, leaving it in a hopeless situation by mid-summer."
Soil preparation is key
Due said that correct soil preparation is a key. "Deep ripping is not always the best plan, it may be better to cultivate the entire surface to a depth of, say, 15 inches." Soil preparation plans should also be made after consulting with a soil specialist.
Due, who emphasized that he was only drawing on his own experience, said that some sort of mulch is fundamental. "Firstly, because the surface layers of soil are often the most easily penetrable and allow the fastest growth for the vine in the first few weeks. In my opinion, a vine with a good start, even if the roots are in the 'wrong' place is much, much better off. It then has the capacity to exploit deeper parts of the profile. Mulch allows maximal use of the shallow parts of the profile by maintaining moisture there. Secondly, mulch conserves water at depth. In some profiles, especially sandy ones, temperature fluctuations in the profile cause water vapor to be drawn from depth to the surface, where it is lost." As for the kind of mulch, he said that most all mulches seem to work equally well, either organic mulch or plastic.
He also warned against using fertilizers that cause root branching, such as nitrogen. "This results in a dense, finely branched root system that cannot exploit deep moisture reserves. The root system you want is a few long roots going deep." He also recommends the use of grow tubes, which reduce water loss from the vine.
"Now, think about the whole package. All the soil-stored water can only go to the atmosphere via the vines' roots, up the stem, and out of the leaves into the humid atmosphere of the grow tube, then into the atmosphere. Every drop of water in the soil is available to keep stomata open and allow carbon production and hence vine growth. Every bit of vine growth produces more roots that exploit more soil and find more water. Properly managed in this way, an un-irrigated vineyard can be brought into production almost as quickly as an irrigated vineyard--30 months to first crop is possible," Due said.
With this complete system in place, Due believes supplementary water is a waste of time. "If the site is good, you won't need it. Temporary irrigation is almost as expensive as permanent. Furthermore, watering vines that will be come un-irrigated only confuses the issue--from the grower's viewpoint and the vines'."
Long term, Due said that vineyards he has established for dry farming have performed very well, typically at about 3 tons per acre.
Obviously, there are areas where dry farming is not feasible, either for economic reasons or because of soil conditions, but it is an option that should be looked at by growers, for both water conservation and, according to some, wine quality as well.
Larry Walker would like to hear your experiences with dry farming winegrapes. Please e-mail him through firstname.lastname@example.org.
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