Bob Sessions walks up the steep, rocky slope of the just-cleared once-forested hillside and says, "We think this could be a great site for Pinot Noir."
Sessions ought to know. He has been the winemaker here at Hanzell Vineyards for a quarter of a century, farming 32 acres above the Sonoma Valley and making some of the best Pinot Noirs and Chardonnays in Sonoma County.
"The land," Sessions says, "is situated properly, facing south, and the soil looked good, plus we're in Sonoma Valley. This is our coolest vineyard, and Pinot Noir loves cooler weather."
But Sessions' own knowledge and experience weren't enough to OK the clearing of oak trees and madrone from these five acres. The winery couldn't afford the financial risk (clearing plus planting would run $105,000 to $130,000)without some guarantee that the land could bear fruit great enough to make great wine and, more important, that the site could be profitable for Hanzell.
How do you guarantee something like that? Maybe you can't, but these days, many wineries are trying to improve the odds with space-age tools, computer modeling and a phone call to Paul Skinner, president of the Napa-based vineyard consulting company called Terra Spase.
Skinner, dressed as usual in jeans, shirt and thick woodland boots, walks along with Sessions on this tour of the Hanzell vineyards. He works not only with Hanzell but with people from dozens of other California wineries, among them Hess Collection, Forman, Domaine Chandon, Peter Michael, Louis Martini, Bouchaine, Opus One, Joseph Phelps, Caymus and Beringer. What's more, his service is revolutionizing the growing of grapevines and the making of wine.
Skinner's company is the only one working for the wine business on subsoil analysis, a relatively new area of agricultural research, though other companies are beginning to offer similar services to other fruit and vegetable producers, and the technology is advancing quickly.
One of the first things Skinner usually does for a winery is send low-flying planes over vineyards to take multi-spectral photos that are then analyzed to determine low-yielding vines and poor growth patterns. Some wineries simply buy these photos, which clearly show which vineyard blocks are most productive and which are most problematic.
Terra Spase also can set up a series of "weather stations" in a vineyard to test soil and air temperature, soil and air moisture, soil permeability (the ability of water to move through the soil) and even such things as leaf wetness, to test for the risk of mildew or mold.
A Terra Spase employee, wearing what looks like a "Star Wars" spacesuit with a satellite transmission unit and carrying a specialized portable computer (called the Hammerhead Telepad, developed for use in the Gulf War), sends data via satellite to the Terra Spase computer in Napa.
"We look for a link from the data to explain why we have no fruit, or no color, or no sugar in the grapes," says Skinner, who has returned with Sessions to the porch of Hanzell's winery.
The "weather stations" can relay information to the computer literally minute by minute, allowing the grower to adapt quickly to radical weather changes that could cause problems for the vines.
What sets Terra Spase apart is that its vineyard trouble-shooting extends to the depths of subsurface layers of soil under the grapevines. On the Hanzell porch, with a view of a sloping vineyard, Skinner opens a 50-page book he prepared for Hanzell. The page shows a three-dimensional map of the subsoils with the pH levels at various depths in one of Hanzell's vineyards. The next page is a map showing potassium levels; yet another map shows phosphorus content.
The maps indicate that in a single small vineyard, many soil conditions are present and that the vines at one end of a block are subject to different subsurface conditions than vines even a few yards away.
Using the maps--which are done by digging holes to about 6 feet, taking soil samples at various depths, then testing them for more than a dozen elements critical for plant development--different vine rootstocks can be chosen to maximize the uptake of the proper nutrients under different soil conditions.
Sessions is using the maps and Skinner's other technology not only to plan his new vineyard but also to solve a problem in an existing one. The vines on the western side of the ranch, Sessions says, should have been more productive than they were. It looks as if some sections of an otherwise fine Chardonnay vineyard had a virus, and the vines produced very little fruit, less than a third of the three tons an acre you'd expect.
Subsurface mapping is most often done when a winery or grower has already decided to replant a vineyard because of low yield or poor quality or because the vines are diseased or under stress from soil-based predators such as phylloxera or nematodes.
Says Hanzell's Sessions: "In our new vineyard, we will be guided by the data we get from Paul's computer and we'll choose the rootstocks that best perform in the different subsoil conditions that we see on these maps."
After the new vines begin to bear a crop, the vineyard should be free of problems: "We don't think we will have to do any radical treatments [to the grapevines]," says Sessions, "once they are established and producing."
It's true that there are no guarantees in the wine business, but Sessions thinks Skinner and his high-tech advice have greatly improved his odds.