Ernest "Bubba" Beasley uses an auger to collect a soil sample from among cabernet franc vines at Pollak Vineyards in Greenwood, Va. All other factors being equal, grapes grown in different soils at Pollak produce wines with markedly different flavors. (Dave McIntyre)

“Let’s go dig a hole!”

Ernest “Bubba” Beasley grabbed an auger and led the way along the vine rows. We were at Pollak Vineyards in Greenwood, Va., west of Charlottesville, on a sweltering summer day last July. Beasley, a geologist, and Lucie Morton, a viticulturist, wanted to show me their research on the relationship of vineyard soils to wine quality. And that meant a “dirt tasting.”

Morton and I clung to the thin, cool shade of the vines, dodging the beads of sweat flying off Beasley’s forehead each time he twisted the auger deeper into the earth. After every few turns, he dumped a cork-shaped plug of dirt onto a garbage bag he’d stretched on the ground. When he had dug a three-foot hole, we took a look. Beasley checked the dirt against a Munsell soil color chart, a geologist’s standard reference that resembles the color chips at a paint store. The soil here was heavy clay.

Then Beasley led us about 50 feet up the row and repeated the process. Here, the soil was visibly different: clay on the top but a gravelly loam farther down, an assessment verified by matching the soil’s colors to the chart.

“This soil allows the vine roots to dig deeper, and water drains better here than it does in the first sector,” Beasley said.

Back in the winery, we tasted two vintages of cabernet franc, 2013 and 2014, made from grapes grown in each soil type. The wine from the clay soil was light ruby in color, with straightforward flavors of bell pepper and bing cherry — flavors familiar to fans of Virginia cabernet franc. The wine from the gravelly-loam-and-clay mix was darker, more savory, with impressive depth and complexity. The second wine was noticeably better in both vintages. The grape variety, viticulture, winemaking and climate conditions were identical; the only difference was the soil.

“You’re not tasting the dirt, per se, but the mineralogy of the soils clearly affects the flavor and quality of the wines,” Morton said.

Beasley, 33, and Morton, 65, make an odd couple of viticulture. He’s a University of Georgia-trained geologist who uses high-tech electromagnetic imaging along with traditional digging to create an underground map of a vineyard site, a technique he calls “ground truthing.” Morton learned viticulture in the 1970s at the University of Montpellier in France and is one of this country’s leading ampelographers (expert in grape varieties). She consults for several high-profile Mid-Atlantic wineries, and she recently began using a drone to combine aerial photography with Beasley’s sub-surface imagery to create comprehensive maps of vineyard sites.

To wine lovers, the vineyard’s effect on a wine’s quality seems self-evident. Yet “terroir” is many things, including sun exposure, microclimate, even the personality of the winemaker. Morton and Beasley are focusing their research on one aspect: the soil. Recent scientific studies have tried to disprove the idea that minerals in the soil end up in the wine, but Morton and Beasley argue that soil characteristics have a direct effect on how the wine tastes.

And their research, in collaboration with scientists Clifford Ambers and Lance Kearns and funded by the Virginia Wine Board, has focused on potassium in particular. The clay soil that yielded the lesser wine in their experiment was significantly higher in potassium than the gravelly subsoil in the other plot. High potassium levels — common in Virginia vineyards — can lead to poor color and low acidity in wine while leaving the wine vulnerable to spoilage. Yet many grape growers add potassium to their soil. That’s because traditional soil analysis, aimed at cash crops such as corn, looks only at the surface soil. Vine roots grow deeper, where potassium levels may be higher.

Beasley and Morton will present their research in March at the Eastern Winery Exposition in Lancaster, Pa. Morton says she hopes they can persuade growers to look deeper into their soils and stop adding potassium.

Sounding like someone exasperated for having to belabor the obvious, Morton says, “Grapes are not corn.”

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