In 2014 you told winegrape growers: “Your irrigation needs are less than you think.” Can you elaborate on that?
In my experience, I have found that most growers can substantially cut back on the amount of irrigation they apply to their vineyards. In fact, I can’t think of any vineyard that I haven’t been able to cut back on irrigation applications. Growers can be nervous that cutting back on water can reduce their yields and I won’t lie to you: I’ve made a few mistakes in the past where we did negatively impact yield. But I’ve learned through experimentation and by exploring new techniques that we can avoid yield loss and still irrigate with a small fraction of what they used to use. In fact, I am convinced that delaying irrigations as late as possible into the spring or summer encourages root development, making vines less dependent on irrigation and less prone to yield loss. I’ve found some vineyards where yield actually increases.
To make a long story short, many if not most growers in the North Coast can reduce their irrigation applications by 30 to 50 percent with only positive outcomes. They just need to learn how to do it.

Why is it important for winegrape growers to measure moisture in the soil?
I’ve always been a big proponent of monitoring the vine, since it is the target of our farming. But, knowing soil moisture has allowed me to up my game significantly and avoid those problems I had earlier in my career. We use devices that measure moisture content at several depths in the soil. It allows us to observe root uptake of moisture in the soil, to know how much moisture is in reserve in the soil “bank,” to know how deeply moisture percolates during an irrigation event, and how long it takes for that moisture to be taken up by the vines. It’s allowed a dimension of precision to our irrigation practices that we otherwise would have to guess at.

How does managing water in Sonoma County differ from other regions and the state in general?
Sonoma County receives a tremendous amount of rainfall during the winter and spring. Even during the recent drought, we received enough rainfall to fully moisten the soil throughout the root zone (about 3 to 4 feet). Because of that, we do not need to irrigate during spring in most years and we can usually delay our first irrigation until mid-summer or even later than that. Most other regions of California do not receive rainfall so abundantly and must irrigate earlier and therefore more than we do in Sonoma County. I think this creates vines that have stronger root systems, use less water resources, and are more reflective of their terroir than in regions that are more dependent on irrigation.

How common (or uncommon) is it for growers to monitor water usage?
Not very common – about 10 percent or so of growers statewide use instruments to monitor vine water stress or soil moisture. But, monitoring of vines, soil and water usage is growing substantially. Perhaps I have something to do with that, but I’m not the only one preaching the benefits of these techniques.

How successful is dry farming (and do winegrapes really need to be irrigated)?
Some vineyards can be dry-farmed and Sonoma County is full of them. It depends on a lot of factors, such as wine style and yield objectives, the capacity of soils to hold moisture, and the ability of the grower to reduce competition for water from weeds. There are many vineyards that simply cannot get through a season without irrigation, but I have also found many vineyards that did not need to be irrigated, unbeknownst to the grower until we worked together.

Who or what inspires you and why?
This is a big question as there are almost unlimited sources of inspiration for me. My family has always been an inspiration to me. My parents always pushed me to do my best and my father never seemed to be quite satisfied with his or my work. Hence, I am never satisfied with the status quo and always strive to do everything just a bit better next time. I think I try to provide the same inspiration for my two kids, always setting the bar just a notch higher than where it is now for them. In so doing, I want to provide them a good example of a strong worth ethic, attention to detail, and relating to other people with honesty and respect. Inspiring them is an inspiration to me.  SD

Viticulturist Mark Greenspan, Ph.D., owner of Windsor-based Advanced Viticulture, has 25 years of viticultural experience, comprised of scientific, technical and practical field efforts. He is regarded as one of the world’s leading experts in winegrape irrigation and has extensive experience in vineyard nutrition, crop load management, vineyard uniformity, soils investigation, vineyard design, grape maturation, climate and viticultural technologies Arista Winery in Healdsburg began working with Greenspan two years ago to help with the overall health, balance and establishment of their relatively young estate vines. “Within the first year we began to see our vines responding to our inputs,” said Mark McWilliams of the Arista Winery family. “We saw more consistency in our shoot growth, length, and overall canopy balance, which has a direct and immediate impact on quality. We saw a huge decrease in our overall water usage though tools like soil moisture probes, pressure bombs and porometers. The result was less water used, balanced crop load, and much more balanced flavors and chemistry in our grapes.”

Arista Winery Winemaker Matt Courtney added: “Being able to quantify vine water status, using Mark’s tools and expertise with those tools, has been an enormous help in making irrigation decisions, in particular. It takes the guesswork out of the irrigation program. With Mark, we’re able to very accurately track the status of water stress in the vine and give them exactly the amount of water they need throughout the season, and we’ve seen immediate positive results in wine quality.”