A Dry Argument: Wine, Irrigation and Terroir | Wine-Searcher News & Features – Wine-Searcher

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© Tablas Creek
| Dry farming is common in the US, where regions like Paso Robles get very little rainfall.Water is essential to life, but vineyards can flourish with a surprisingly small amount of it.
Water is a critical aspect of grape growing, affecting how vines grow, how grapes develop and how wines taste.
For dry farmed vineyards in many regions, the amount of moisture received in a given year can be a major factor in determining the character of the vintage, and therefore how terroir is expressed.  In regions where dry farming is impractical or impossible, vineyards are irrigated – humans, not nature, control water.

What then, can be said with regard to irrigation and terroir expression, with such an important part of the picture being controlled by humans, rather than nature? What do terroir-motivated growers in dry regions do to minimize their own impact? In what ways does irrigation affect vines, roots and wines?
Irrigating vineyards is nothing new. In fact, wine historian and archaeochemist Dr. Patrick McGovern says that "once the grapevine was domesticated, irrigation systems were probably devised. Domesticated grape seeds and wood from the 4th Millennium BC have been recovered from the relatively dry Jordan Valley (then Jericho) – where the wild vine did not grow – and which attest to vineyards and a thriving wine industry there, likely depending on irrigation.  From there, viniculture was transferred to the Egyptian Nile Delta around 3000 BC, where a kind of 'drip irrigation' is likely shown on tomb reliefs [artwork] of the time.  Similar developments occurred as the domesticated grapevine was progressively transplanted south to lowland Mesopotamia with it extensive irrigated fields and gardens, reaching Shiraz in the 3rd Millennium BC."
How does water access (regardless of source) affect how wine tastes? In endless ways. As one example, during ripening, access to more water will slow a vine's reaction to warm temperatures, slowing ripening, sugar accumulation, acid loss and aroma changes, and the opposite can be said for drier conditions. These can make a big difference in the resulting wine's character and chemistry. Another, more extreme, example: in drought years, canopies may be short, stifling sugar accumulation, and water stress may cause increased fruit character. Tannin profiles, berry size and yield are also affected by the amount and timing of water access. With irrigation, one can control many of these factors, say, by applying water during a heat spike.  These are just a few examples, but the effects of water on vines and wines are far reaching.
Hydroponics or terroir?
Still, there are many critical aspects of terroir that water does not directly effect – such as temperature, soil type, aspect, slope, latitude (light intensity) and wind patterns. However, water availability has an indirect effect on how all of these affect grape development – and vice versa: it's all interconnected and very complex.
"There are two types of irrigation," says Dominique Roujou de Boubée, owner of Terroir en Botella, who consults for organic vineyards around Spain "One to increase yield...and the other as a tool to manage a terroir driven wine in warmer, drier climates – to avoid the shutdown of photosynthesis."
Where yield increases are the goal, he says "the industrial vineyards know exactly what the vines need at every moment [water, nutrients, and so on], and they reach good ripeness with higher yields, but of course, without any terroir influence – however they have good results and can make a huge amount of impersonal, cheap, fruity and industrial wine." 
This is essentially hydroponic grape growing. In vineyards where irrigation is necessary, but terroir is a concern, he says: "I think we can have terroir expression with judicious and precise irrigation. The problem is measuring and monitoring it, which isn't the easiest."  It takes a keen eye, or training with certain water monitoring tools.
There are creative ways growers can minimize their irrigation and better mimic dry farming, giving just what extra the vines need that nature doesn't provide. Ron Mansfield, owner of Goldbud Farms in Placerville, California manages many vineyards in the El Dorado AVA. Mansfield farms a handful of sites that share a deep, volcanic clay soil, which only need irrigation in some vintages. Clay retains water (and nutrients) better than silt or sand, allowing this to be possible – on sandier sites in Ron's region, more irrigation is necessary.
"We may irrigate depending on weather and temperatures later in the growing season, but if things are mild enough, you can get by with no irrigation," Mansfield says. He watches the vines closely, considering "how they perform, how the canopy grows, how quickly they fill their space. If they're lagging behind, we'll give a little water." 

© Terroir en Botella
| Dominique Roujou de Boubée believes that irrigation can control terroir.His goal in these years is to give the vines the minimum they need to be happy. "We usually only water right around veraison. That seems to work well, in that it doesn't invigorate the vines, but helps them hold onto their canopy a little longer and mature the grapes." 
Water-stressed plants drop healthy leaves as a defense mechanism, and without leaves to photosynthesize, progress stops. Ron also likes to give a good watering after harvest, prior to dormancy, giving the vine a boost in a way that avoids affecting the current vintage's grapes. The vines "have worked their butts off all season long, and our approach is to help that vine get into dormancy".
Building a thirst
Tablas Creek in Paso Robles uses a different irrigation strategy. Depending on winter rainfall, they may water up until flowering, but "post fruit-set, we pretty much cut water off until we start seeing visual cues of stress, such as short tendrils, or cupping of leaves. Once veraison starts, the water is turned off again to assist in sugar loading," explains Jordan Lonborg, Tablas' viticulturist.
Tablas Creek actually has a very unique situation, which offers many insights; they farm both irrigated and dry farmed vines on the same estate. This is a rare opportunity to compare the differences that may result, but it is critical to keep in mind that this is one example: it would be incorrect to think that the take-aways from Tablas Creek are applicable to all, or even many, sites.
It can get hot at Tablas Creek and 105F isn't uncommon. One might imagine that the dry farmed vines would struggle for water more than the irrigated vines during these periods, but at Tablas this isn't the case. "I can speculate that's because such a large portion of the dry-farmed roots are deeper, where it's cooler," says Jason Haas, partner and general manager at Tablas Creek. "It could also be that the irrigated vines [planted to higher density] are competing with each other. After a week of 105F we may lose a big percentage of irrigated Mourvèdre grapes to sunburn, and the dry-farmed vines grapes are fine."
This counterintuitive result continues to the glass as well. Neil Collins, winemaker at Tablas Creek, says: "I anticipated that the dry-farmed wines would be bigger and more powerful [as they don't receive irrigation or summertime rain], and that didn't happen. The irrigated wines are the bigger and more tannic, the dry-farmed wines have a little more complexity and finesse."
Again, these results may be unique to Tablas Creek's terroir and irrigation practices. They have good clay and limestone content, especially at depth, which retain water extremely well, and they also irrigate very lightly. On sandier dry-farmed sites, where the irrigated blocks were given more water, the opposite might be true.
Perhaps the most interesting observation, and one that is more applicable to other sites, is that even with light irrigation, like at Tablas Creek, irrigation can significantly impact where roots grow within soil. "The roots go where the water is” says Jordan. "The dry-farmed root systems web out and grow downward into the soil profile. The irrigated vines' tap root basically goes down 12 inches, makes a 90-degree turn and goes along the vine row, with feeder roots every three feet that correspond to our drip emitters."
This is noteworthy because the makeup of soil changes, often dramatically (though not always), at different depths. Thus, irrigated and dry-farmed roots can occupy very different segments of a soil profile, which may mean different soil type (such as sand vs clay), amount of organic material, mineral content, water availability and soil temperature—all of which affect how vines grow and ultimately how wines taste.  As Haas points out, "topsoil [where most irrigated roots are likely to reside] isn't very unique, it's mostly decaying organic matter". 
At Tablas specifically, as roots go deeper, they are in increasingly limestone rich portions of soil. So, the difference between dry-farmed and irrigated vines goes beyond just water availability, but, may entirely change the root structure and soil environment that roots occupy.
This is not to imply that irrigated vines lead to inaccurate representations of a vineyard's terroir. On the contrary, most aspects of terroir are not directly affected by water.  As evidence: both the dry farmed and irrigated wines from Tablas Creek taste like Tablas Creek. But, just as there are differences in how vines grow when irrigated or dry farmed, there are also differences in how the resulting wines taste. Regarding the dry-farmed wines, Collins says: "Is it a better expression of our terroir? I don't know if it's better, but it's purer. The less influence from us, the purer the expression of the land."
He also brings up a good point: "Whether it's better or not is for individuals to decide." In other words, purer terroir expression is not the same thing as better wine; these are separate discussions. There are plenty of dry-farmed, old-vine sites in California that produce solid, but not especially interesting wines. On the flip side, many of the most intriguing and revered wines in the New World come from irrigated vineyards. The former may be more complete representations of their land, while the latter may be the better wines. Additionally, many exceptional wines are made in regions where dry farming is not an option, so irrigation creates the possibility of any expression of those great sites.
Irrigation, then, does not preclude terroir, however, it does change various aspects of it.  But, dry farming isn't free of human influence either.  “We have a lot of tools to manage both types of systems”, says Jaco Engelbrecht, viticulturist and owner of Visual Viticulture in Wellington, South Africa.  For dry farming, he notes  “soil preparation, planting techniques, organic matter, mulching, rootstock choice [some are drought resistant] and grape variety (isohydric varieties like Grenache does better dry farmed than an-isohydric varieties like Syrah)”.
This all brings us back to the reminder that terroir is, at best, an imprecise idea, and that there is no pure or true expression of any terroir – human influence is inherent to viticulture. Where irrigation is necessary, there are practices interested and creative growers can do to rely on nature's influence as much as possible, and beautiful wines are created in a myriad of ways.
Like most aspects of wine, water availability and its effects are complicated, and give the wine geek much to ponder with regard to the nature of wine.
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