Dry farming has become a relatively new buzzword in the wine industry, with supporters touting it as the road to better wine & a better environment. I thought it was worth taking a look at dry farming and irrigation to see if I could sort out some of the truth from the hype. What is dry farming? What are the benefits and risks of dry farming versus the benefits & risks of irrigating? Is there any middle ground?
While there doesn’t seem to be a regulatory definition of dry farming, there are some basic guidelines. Here’s my best try at a definition: dry farming is crop production that relies on residual soil moisture during dry seasons. Some people say that it should be “soil moisture stored from precipitation,” but I believe that natural snow melt that is not channeled by man is a legitimate part of dry farming. Many practice a version of dry farming that says “we only irrigate in years where we must to avoid losing the crop.” While I understand the sentiment, & generally agree with the approach, I’m not sure they are really dry farming. Being a mostly dry farmer may be like being a little pregnant.
The first viticulture was probably dry farming, but it didn’t take long for irrigation to join the party. It is believed that wine making began around 7,000 years ago. The Areni 1 Winery currently holds the record for oldest known winery at 6,100 years old. Irrigation was definitely practiced for some crops starting around 5,0000 BC (equal to the beginning of viticulture). The first known irrigation canals specifically for viticulture are over 2,600 years old in Armenia & in Egypt. Of course, there may be much older sites waiting to be discovered.
Before examining the strengths & weaknesses of dry farming, it is probably worth establishing where you can & can’t dry farm. It also might help to have a general baseline for the main grape growing climates.
There are three basic climates associated with grape growing & wine making. They are Maritime, Continental, & Mediterranean climates. Each has its own water issues. Maritime climates tend to have a moderate climate tempered by the effect of a large nearby body of water. They have warm, but not hot summers & cool, but not cold winters. Classic Maritime wine regions include Bordeaux, most of Oregon, Rias Baixas, & New Zealand. In a Maritime climate, the rain concern is too much rain, particularly during the growing & harvest seasons. They also can have high humidity, which promotes mold, mildew, bunch rot, & nematodes, among other hazards to grapes. Irrigation in Maritime climates is generally only necessary in unusual drought years. Mediterranean climates are characterized by a long growing season with little temperature shift. The winter is generally warmer than Maritime or Continental winters. Most rain comes during the winter. There is very little rain during the growing season, which prevents a variety of problems, but increases drought issues. Mediterranean areas are more likely to use irrigation during the summer ripening stages. Classic Mediterranean regions include Greece, Tuscany, Provence, Sonoma, & the Napa Valley. Continental climates tend to be inland & away from large bodies of water. They can have very cold winters & very hot summers. Rain falls mainly in the winter & spring. Areas with soil that has good water retention generally don’t have water issues. Areas with soils that don’t retain as much water (granite for instance) may have water issues during the summer. Continental growing regions include the Columbia Valley, Texas High Plains, & most of Austria.
There are a few requirements to dry farm grapes. Some are under control of the producer & some are not. The most basic is rainfall (including snow melt). There is general agreement in the scientific community that 20 inches of rain per year is the cut off point for regular dry farming. Sites with 15 inches of rain might work with just the right soil or rain at just the right time, but it is likely that emergency watering will be needed more years than not. Oregon based dry farming advocates The Deep Roots Coalition & a couple of other advocates consistently list Santorini as an example of dry farming being possible with 4-10 inches of rain, but if you look up Santorini rain fall, you will see that they get almost 22 inches a year. When the rain falls is important. Rain in spring and summer matters because that is when you have flowering and fruit set. In Tuscany, the vines receive about 8 inches of rain during this time compared to 2.4 inches in Napa. If the soil can’t retain the water from winter rains, that isn’t enough for the vines.
Dry farming requires soils with moisture retention capabilities. The California Ag Water Stewardship initiative compares it to the same considerations as picking a site for a pond. Sandy soils or heavily fractured soils do not work well. Clay & sandy loam are great at retaining water. Deep soils where vines can burrow down are important. The deeper roots allow the vine to work its way down to stored water. “Nothing is drought tolerant on shallow soils,” says Andy Walker, a professor at the University of California-Davis Department of Viticulture and Enology. Dave Osgood, who dry farms in Paso Robles says “See what grows there naturally. If it is only dry grass land, then it may be hard to dry farm, but if you have oak trees, shrubs, flowers, and grasses, then you have water in the soils.”
Rootstock selection is also important when dry farming. St. George rootstock seems to be the preferred rootstock for dry farmers due to its drought resistance. It isn’t as popular in some areas because it reduces yields, but dry farmers aren’t looking for high yields anyway. Rootstocks can make it difficult to switch an existing vineyard over to dry farming. After the AxR1 debacle in California (a rootstock that turned out not to be Phylloxera resistant), many vineyards were replanted with a riparian rootstock. Those roots love water, but don’t have drought resistance. To convert a vineyard with riparian rootstock to dry framing would probably require ripping out the vineyard & replanting. That isn’t sustainable from an environmental or commercial perspective.
Trellising, or lack thereof also plays a part. Dry farmed vineyards are frequently bush pruned. This promotes smaller vines with less wood (which means it needs less water). It also allows natural shade for the vine while still having air flow. Vines need to be spaced further apart than in standard modern vineyards. Depending on the soil & rainfall, this can vary from 32-120 feet. You see this in the Toro region of Spain, where the vines are spaced far apart in bush vines to get enough water to survive. The nice side effect of this, is that they never got the Phylloxera louse. Dry farmed vineyards in the California North Coast are spaced at 8 x 8 or 9 x 9 feet intervals, but south in Paso Robles, you need to go to 10 x 10 or 12 x 12 foot spacing.
Finally, some grapes do better with dry farming than others. Vigorous grapes do best, because the reduction of vigor in dry farming just brings them into balance. That means that classic hot climate grapes like Zinfandel, Cabernet Sauvignon, & Tempranillo do well, but grapes like Pinot Noir do not. Barbera is considered one of the harder grapes to dry farm.
With all of that background out of the way, we can finally get to the comparisons. Sorry for all of the buildup! I just wanted to get the ground rules down.
Dry Farming SWOT
- Dry farmed wines probably show a purer terroir. If terroir is everything about the site that makes it unique, then adding anything to it, whether that is water or fertilizer, takes away from that expression.
- There is some evidence that properly dry farmed grapes can be higher quality for wine making than others. Some growers and wine makers believe that dry farmed fruit is sweeter, with more intensely flavored grapes. The grapes tend to have lower yields, which is associated with quality. The berries tend to be smaller, which is advantageous for red grapes because it means the skin to juice ratio will be higher (which means more anthocyanin & tannin extraction). The wines are thought to have more dry extract, which increases ageability. One study noted, “Long-term responses to water shortage include reduced canopy size, increased root-to-shoot ratio, improved water-use efficiency, and altered fruit composition (Chaves et al. 2010).” All of the wines that originally won the 1976 Judgment of Paris that put California on the world wine map were dry farmed.
- If you believe in minerality in wine, then dry farmed wines have a better chance of minerality. The roots go deeper & can extract more minerals. I’m not tackling minerality right now. One controversial subject at a time is my motto.
- As expected, there is a tremendous water savings. 16,000 gallons of water per acre is a solid estimate.
- There is an energy savings. The energy used to transport & pump water for irrigation is eliminated.
- Weeding (or herbicides for non-organic growers) is decreased. Part of dry farming involves tilling the soil & creating a dry layer of soil (called dust mulch) on the top to trap moisture. It is dry enough that fewer weeds grow.
- Money & time spent in establishing & maintaining irrigation is eliminated. Irrigation systems seem to require a lot of maintenance & in my experience, someone is always damaging some aspect of the system.
- The initial installation cost is much less. Dave Osgood says it costs about $6,000 per acre to plant non-irrigated, head pruned vines in Paso Robles & between $30,000-$40,000 per acre to plant with trellising & irrigation.
- The vines may become heartier. CAFF policy director Dave Runsten said, “the vines become self-regulating, which can create resilience to drier seasons and heat events.” (Community Alliance of Family Farmers).
- There are some wineries that will pay more for dry farmed grapes, and some customers who will pay more for dry farmed wine.
- Some argue that dry farming decreases the stomata on the bottom of the leaves and that this leads to reduced sugar/alcohol potential. I have seen no studies that support this conclusion and have seen several that refute it. I’m just including it here because it is a common belief of some dry farming supporters.
- It isn’t possible in some vineyards. Starting new vineyards in Argentina for instance would be virtually impossible without irrigation. Mendoza averages fewer than 9 inches of rain per year and Patagonia veers between 3.5 and 17 inches. Anything less than 10 is considered a desert. Some areas in the eastern portion of the Barossa Valley in Australia average 12.4 inches. East of the Cascades rain shadow in Washington State, vineyards average 6-8 inches of rain. The largest growing area in America would be deeply impacted without irrigation. The southern San Joaquin Valley between Fresno (11 inches) and Bakersfield (6 inches) would not be able to grow grapes.
- Long term water deficits damage vines. One study concluded, “Prolonged and severe water deficit may reduce vigor, yield, and wine quality, and may have cumulative effects on growth and yield formation in subsequent years.” (Matthews and Anderson 1989, Romero et al. 2010, Dayer et al. 2013)
- Heat stress causes a rapid increase in sugar production (up until it shuts down photosynthesis). When the Spanish government decided to allow irrigation, it cited this problem. They observed that heat stress causes rapid sugar accumulation, but the phenolic components, which give the wine its flavor, consistency, and color developed more slowly. The result was that growers were forced to let grapes hang longer to achieve phenolic ripeness. This meant that vineyards that produced 12% alcohol wines in the past, were now producing 14-16% alcohol wines. For those that champion low alcohol wines, this is a problem.
- Vineyards come into production slower. It can take as long as 5 years for a dry farmed vineyard to achieve full production, versus 2-3 years for irrigated vines. This must be taken into consideration when determining startup costs.
- Another economic consideration is yield. While decreased yield may increase quality, if the increase in grape prices doesn’t compensate, it can be disastrous. Philip Coturri, who runs a vineyard management company Enterprise Vineyards that specializes in organic farming said “As an organic farmer, I’m in demand. I pay my workers between $10 to $12 an hour. To do that I must produce a consistent 2.5 to 3 tons an acre. On so many of these properties if I dry-farmed them, I’d get 1.5 to 2 tons. It’s a matter of sustainability.”
- Small berry size is great for red grapes due to the increased skin/fruit ratio, but there aren’t many advantages to small berry size for white grapes.
- Heat stress can shut down some vines. Pat Rohan, who runs a vineyard management company and does some dry farming says, “When we get three or four days of 100°F heat, we need to water Barbera. When Barbera shuts down, it’s done. In contrast, Zinfandel will shut down and come back.”
- Too little water can cause grapes to raisinate. This can change the taste of the wine dramatically. It also takes additional labor or equipment to remove raisenated grapes from the bins before fermentation.
- Dry farming techniques require a lot of cultivation. That is part of the process of creating the “dry mulch” that retains water. For hillside vineyards, erosion can be exacerbated. For dry farmers who otherwise farm conventionally, this can lead to an increased emission of nitrous oxide, which is a powerful greenhouse gas. This isn’t nearly as much of a problem for organic growers.
- There is marketing value in dry farming. It is a way to stand out in a crowded wine market. As mentioned above, there is an opportunity to charge more for the grapes. Tom Holdener, of Macchia Winery in Lodi says that he prefers to buy dry farmed grapes. He said, “Grapes from dry farmed and deficit-irrigated vineyards have good flavors, and I think dry-farmed fruit generally tastes better…. we know that the crop level will probably be in balance in relation to the growing season, and we don’t have to ask the grower to drop crop.”
- Global warming may increase water scarcity and encourage dry farming. As water becomes scarcer and more expensive, there should be a boom in dry farming in areas where it is physically and economically possible. In Oregon, most of the growing regions receive as much as 40 inches of rain a year. There will be pressure to convert to dry farming.
- Global warming won’t be an across the board positive for dry farming. In southern France, the droughts of 2003, 2005, and 2006 had a huge impact on the industry, particularly in the south of the country. Even with irrigation, the producers have faced water rationing. The problems this created have resulted in a decrease in plantings as farmers have pulled vines. The number of hectares under vine has dropped 11% since the year 2000. The is particularly noticeable in Provence, Languedoc-Roussillon, and the southern Rhone valley. Marginal areas for dry farming may become areas where it is no longer possible at all.
- Extended droughts seem to be occurring more frequently. Dry farmed vineyards that are viable with a year or two of drought may not physically or economically survive a 5-year drought.
- If grape costs don’t rise to support dry farming, it may not be economically feasible. Dick Cooper of Cooper Vineyards in Amador says, “Generally, given the costs for production in this area, if you’re not producing 4 tons per acre and getting at least $1,500 per ton, you aren’t going to make it.” There are some grape varietals that just won’t justify that price.
- Irrigation gives the grower options. If there is sufficient rainfall, don’t turn it on. If there is a drought, you have water for as long as your water supply holds out. If you want to practice regulated deficit irrigation (RDI), you have that option. If it looks like frost, you have options. Steve Thomas is the vineyard manager of the 600-acre Kunde Estate in Kenwood, of which 100 acres are dry-farmed. Thomas said that even if he was able to convert to dry farming he would keep the pipes, which cost $1,600 an acre, as insurance and for applying vineyard treatments such as nutrients, fertilizers and pesticides through the system.
- Irrigation permits “growers to adjust water supply to control shoot growth, manipulate fruit composition, and conserve irrigation water” (Chaves et al. 2010, Keller 2010).
- The majority of the world’s grape production regions are in regions where there is water stress. This may be seasonally dry summers where summer rainfall is not enough to compensate for evapotranspiration. It may be areas prone to drought. It may be vineyards in desert climates like Mendoza. Irrigation allows those areas to make wine consistently. Cantina Pizzolato in the Veneto region of Italy says, “The local agriculture is based on the use of irrigation. During this 2017 production year the regions that are not yet allowed to use irrigation have lost about 30% of production.”
- Irrigation has helped with the 20th Century explosion of good quality, inexpensive wine. Temperature controlled fermentation and mechanical harvesters are probably the two most important legs of this stool, but the inexpensive wines from California’s Central Valley or Southeast Australia depend on irrigation. These may not be connoisseur favorites, but they are a key part in the democratization of wine.
- Some people prefer shallow roots. I’m not a huge fan of the concept, but UC Davis viticulture and enology professor Larry E. Williams likes them. “If you’re a grape grower, you want to have that vine dependent on what you do so you can manipulate them,” says Williams, whose academic work focuses on irrigation management. Williams further explained: “Since the vine is getting most of its water from the drip system, then a grape grower has greater control on how much the vine gets water.”
- Irrigation allows growers to achieve greater vine density. This sounds like a way to increase yield, and it can do that, but it is more about emulating Bordeaux & Burgundy. Before the rise of irrigation in Napa, vines were planted at 450 vines per acre. They now are able to reach up to 2,500 vines per acre, which is more like the tight spacing in Bordeaux and Burgundy. There is an idea that the density forces the vines to compete for nutrients & promotes higher quality. I don’t know if that’s true or if it is just a case of looking at how good wine is in those regions and then imitating what they do, but that’s rampant in this discussion (they don’t irrigate in Bordeaux & they have great wine, so dry farming must be the key to great wine).
- Irrigation helps produce the ripe style of wine that is currently popular. “Remember eucalyptus and green bean flavors?” asks Philip Coturri, “Those were due to unripe grapes. To get today’s super-ripe flavors the vines need hydration. Irrigations produce a very different type of wine. Irrigation is a tool for extended ripening.”
- Evidence for water dilution of berries is anecdotal rather than scientific. It appears that it is based on rainfall in Europe rather than drip irrigation. “The evidence in favor of a “berry dilution” effect of late-season water supply seems to come from production regions where high water supply is associated with rainfall rather than irrigation. During rainfall or overhead sprinkler irrigation, ripening grape berries may absorb water through their skin” (Becker and Knoche 2011). “It is unknown, however, whether the berries also import excess water that has been taken up by the roots following drip or flood irrigation. Further, it remains unclear whether excess water close to harvest may lead to an increase in berry size and whether this may alter wine composition.” (Keller, Romero, Gohil, Smithyman, Riley, Casassa, & Harbertson)
- Irrigation can waste precious water. Dave Runsten said, “We’re over-irrigating a lot of crops in California”
- Some argue that it leads to additional work in the winery to correct problems caused by overwatering. Thibaut Scholasch, of Fruition Sciences in Emeryville say that not only is too much water used in vineyards, but that it also impacts the costs in the winemaking process. He thinks it can lead to weaker flavors, less productive vineyards because they require severe cropping to achieve ripeness.
- Irrigation encourages shallow root systems. Although Professor Williams likes a shallow root system, many believe that deeper root systems lead to healthier vines. It certainly gives them more protection if the irrigation supply runs dry during a drought. For those who believe in a direct link between soil minerals and mineral uptake in the vines, deep roots would be preferred. It may also be that the microbes that are part of the terroir are more completely accessed with deeper roots.
- Irrigation allows the practice of regulated deficit irrigation (RDI), also called partial root zone drying. There are different approaches to this practice. One system is to withhold water from the vines at particular times in the growing season to reduce vigor while watering at other times as needed. It also can mean applying water to the roots on one side of a vine, but not on the other side. This causes the vine to promote concentrated fruit growth because the vine is essentially tricked into thinking it is stressed and needs to put out berries, without actually damaging the vine. Under RDI, less water is applied than a vineyard loses to evapotranspiration during a portion of the growing season. Deficit irrigation may result in red wine with more fruit and less vegetal aromas, more anthocyanin pigments, and sometimes lower astringency” (Matthews et al. 1990, Chapman et al. 2005, Castellarin et al. 2007a). “Moderate water deficit in vineyards is generally associated with desirable changes in fruit composition compared with fruit produced under abundant water availability” (Chaves et al. 2007, Keller 2005). “The smaller berry size due to water deficit is often cited as the main reason for such improvements, but water deficit may also alter the biosynthesis of quality-determining compounds independently of berry size” (Castellarin et al. 2007a, 2007b, Roby et al. 2004). “Increased light interception by the clusters due to lower shoot vigor under water deficit may be responsible for some of these changes” (Castellarin et al. 2007b, Chaves et al. 2007, Romero et al. 2013).
- Irrigation is expanding. In 2016 France began to expand the approval of irrigation depending on the time of year and the region. It is generally approved between June 15th & August 15th. For AC vineyards, it must be sanctioned by the authorities for that particular appellation. The driver behind this decision seems to have been global warming. Oddly enough, they do not allow the installation of permanent drip irrigation. This means that they are promoting a much more wasteful form of spray irrigation, but that’s something for another day. In Italy, irrigation is permitted in at least 30 AOC vineyard areas. Roughly 26% of all wine vineyards are irrigated now, with as much as 85% of the vineyards in Tuscany irrigated.
- Irrigation systems with an over the vine capacity can protect against frost. Ted Goldammer wrote in the Grape Grower’s Handbook “Over-vine sprinkler systems involve spraying the vines with a fine mist of water as the temperature falls to freezing. This water then freezes encasing the canes and buds in ice. As the water changes to ice on the surface of the vine, it releases a small amount of heat (known as latent heat) that protects the vine from any damage. Latent heat prevents the surface temperature of the vine tissue from falling below 32 degrees F (0°C). Conversely, when ice melts, or water evaporates, the temperature around the water is cooled. Water evaporating from the surface of a vine will draw heat from that vine.”
- Irrigation may be a response to global warming to preserve growing regions that might otherwise fail. Michelle M. Moyer, PhD. Associate Professor, Dept. of Horticulture, Statewide Viticulture Extension Specialist at Washington State University wrote, “Our researchers would argue that reliance on dryland farming will ultimately result in less resilience to climate change. Irrigation is a tool growers use (often in dryland areas as well, to make it through years of drought) to help mitigate inconsistent weather patterns.”
- Global warming may make irrigation less reliable. Growers who have been dependent on wells may be out of luck when the well runs dry and the shallow roots of their vines can’t compensate for the loss of water. Water will become more precious as the earth becomes drier. The cost of water for irrigation will increase and even then, its availability may decrease. Brendan Lowe writes that this year in South Africa “The water sources most wine producers in the area rely on for irrigation have been rationed for months, with quotas cut by as much as 80 percent, forcing producers to move up vine replacement schedules, introduce water-saving devices in cellars, and use water for only the highest-income blocks—if there’s water left to use at all.” This isn’t a theoretical issue that may or may never happen. It is occurring right now.
- Much less concerning is that irrigated vines may be at a marketing disadvantage compared to dry farmed vines. If the price of dry farmed grapes/wines climbs high enough, then all of the money invested in irrigation won’t pay for itself.
Obviously, this is a complex issue. There are those who want to make it black and white and say that one side is always right and one side is always wrong, but it just isn’t that easy. If someone tells you that everything should absolutely be done one way, you probably want to get a second opinion (especially if they tell you that irrigation always increases sugar/alcohol).
I think that the best answer is probably somewhere in between. I love wines from areas like Mendoza Argentina and I want them to be able to continue to make them. That requires irrigation. What I really want, is for growers to use the most efficient systems possible. The old systems that they are using in France aren’t a viable long-term solution. Underground or drip irrigation is where anyone who irrigates needs to migrate.
I also think that people who are consistently watering despite receiving 30 or more inches per year are wasting a precious resource. If you use the minimal amount of water to produce the best quality wine, I think everyone should be happy. Irrigation doesn’t have to mean high yields, water waste, and inferior quality wine. Done correctly, it can help create delicious wine.
I think research and experiments are necessary to find the best ways to grow grapes using the minimal amount of water. That means looking at everything from root stocks, to varietals, to organic practices, to trellising options, to tons of things that I’m not sharp enough to know. Most vineyard managers accept climate change as a reality. We need to prepare for grape growing in a hotter, drier world. If we do that correctly, our grandchildren can toast that success with a nice glass of wine.
I looked at a ton of sources to get my head around this. Here are some in particular that I referenced. Not all of these really made it into what I wrote, but they informed me along the way. There are plenty of other sources I have read or listened to over the years, but these are the ones that I specifically looked at for this. I apologize if I forgot someone.
https://modernfarmer.com/2015/12/dry-farming-wine/ The Benefits of Dry-Farming Wine—For the Palate and the Planet By Hannah Wallace on December 21, 2015
http://c.ymcdn.com/sites/www.wawinegrowers.org/resource/resmgr/Winegrowers_Water_Availabili.pdf Washington Wine Growers Water Availability Policy Statement
https://daily.sevenfifty.com/how-south-africas-wine-industry-plans-to-survive-the-water-crisis/?utm_campaign=SevenFifty%20Daily%20Weekly%20Digest&utm_source=hs_email&utm_medium=email&utm_content=61290652&_hsenc=p2ANqtz-8xGseD5Hz94l5IWA1wje30jFJQ6eXpiiWlLyPa8mEsxBCGA_AHI2ZX4Hh4OpEKWNhAxtoE8N1lnv247ykeRMhUIulsEQ&_hsmi=61290529 How South Africa’s Wine Industry Plans to Survive the Water Crisis
https://oeno-one.eu/article/view/1699 Strategic irrigation management in Australian vineyards Peter R. Dry, B. R. Loveys, M. G. Mccarthy, Manfred Stoll
http://quench.me/longform/maritime-climate-affects-some-of-the-worlds-most-coveted-wine-regions/ September 15th, 2017/ By Treve Ring Maritime climate affects some of the world’s most coveted wine regions
https://news.nationalgeographic.com/news/2011/01/110111-oldest-wine-press-making-winery-armenia-science-ucla/ Earliest Known Winery Found in Armenian Cave By James Owen, for National Geographic News Published January 12, 2011
https://www.guildsomm.com/public_content/features/articles/b/gregory_jones/posts/climate-grapes-and-wine Climate, Grapes, and Wine Terroir and the Importance of Climate to Winegrape Production Gregory Jones 12 Aug 2015
http://www.growingproduce.com/fruits/how-to-dry-farm-winegrapes/ Kendall Lambert is the Water Program Coordinator for Community Alliance with Family Farmers.
https://www.winesandvines.com/news/article/115248/Economics-of-Dry-Farming-Winegrapes 04.21.2013 Economics of Dry Farming Winegrapes Amador and Lodi, Calif., growers discuss practices for quality wines and water conservation by Jon Tourney
http://agwaterstewards.org/wp-content/uploads/2016/08/Turning_water_into_wine.pdf Turning water into wine To water grapevines or not — the roots of the wine industry’s next great controversy Alice Feiring, Special to The Chronicle Friday, June 1, 2007
http://agwaterstewards.org/wp-content/uploads/2016/08/A_new_path_to_using_less_water.pdf In Napa, a new path to using less water Jon Bonné Sunday, March 21, 2010
http://www.caff.org/wp-content/uploads/2015/05/CAFF-Presentation.pdf Dry Farming Wine Grapes in California Dave Runsten Community Alliance with Family Farmers August 7, 2015
Irrigation Management of Winegrapes with a Limited Water Supply In: ucmanagedrought.ucdavis.edu Terry Prichard
https://www.jancisrobinson.com/articles/irrigation-now-official-in-france Jancis Robinson 11 Apr 2007
http://irrigazette.com/en/news/irrigation-grapevines-europe-update-existing-legislation The Irrigation of grapevines in Europe – an update on existing legislation By Fleur Martin, Irrigazette
https://www.bkwine.com/news/irrigate-or-not-in-vineyards/ To irrigate or not to irrigate in the vineyard? by Britt Karlsson on September 4, 2014
http://www.lodigrowers.com/considerations-for-dry-farming-wine-grapes/ Lodi Grape Growers Association Stan Grant
https://naturalmerchants.com/organicwines/dry-farmed-wine/ Ed Fields CEO Natural Merchants
http://www.latimes.com/business/la-fi-dry-farm-wine-20141123-story.html Drought revives ‘forgotten art’ at wineries: Farming without irrigation By David Pierson Nov 22, 2014
Deficit Irrigation Alters Grapevine Growth, Physiology, and Fruit Microclimate study by Markus Keller,1* Pascual Romero,2 Hemant Gohil,3,4 Russell P. Smithyman,5 William R. Riley,5 L. Federico Casassa,6,7 and James F. Harbertson6
Talks by Gregory Gambetta Sciences Agro professor of viticulture working as part of both Bordeaux Sciences Agro and the Institut des Sciences de la Vigne et du Vin.
Michelle M. Moyer, PhD. Associate Professor, Dept. of Horticulture Statewide Viticulture Extension Specialist Washington State University – IAREC via email