Stag’s Leap Wine Cellars
Kirk Grace—our 'hands-on' vineyard manager.
Farming The Soil
Although harvest is one of the most exciting times of the year in the vineyard—signaling the culmination of a growing season and the anticipation of new wines— what happens on the ground after harvest is equally important. It sets the stage not only for the coming growing season, but for the health of the vineyard itself, and ultimately, the quality of future wines. "At harvest we’re farming the vine; immediately after harvest, as the vines enter dormancy, we farm the soil," says Vineyard Manager Kirk Grace.
Kirk, who views vineyard soil as a "savings account of biological life," focuses on two major activities post-harvest: amending the soil and planting cover crops. Both are designed to, as he says, "feed the soil, not the vine." They replenish nutrients in the soil, ensure healthy soil structure and conservation, and create an environment ideally suited to healthy grapevines. Everything he and his vineyard team do is with an eye to optimizing the quality of the grapes, both in the coming growing season and in years to come.
Amending vineyard soil involves creating different mixtures—of compost, humus (organic matter), rocks and minerals—and spreading them through the vineyard. By walking the vineyards throughout the growing season, taking soil samples at different growth stages, and most importantly, observing the vines’ growth patterns, Kirk decides which soil "mixtures" will perform best in which areas of the vineyards.
"Amending the soil can’t—or shouldn’t—be done with a one-size fits-all approach," says Kirk. "It needs to be very individualized— more of a vine by vine approach." Where one soil mixture may have more compost, another may have a higher component of a certain type of rock or mineral. Each mixture is custom designed for the needs of each particular vineyard or section of vineyard, and is spread through the vineyard according to his precise specifications.
The same approach holds true for cover crops. We use three types of cover crop mixes, an annual grass and sub-clover mix including mustard; a large-growing invigorating mix; and a de-vigorating perennial grass, depending on the growing habits and needs of each vineyard block. Cover crops are planted as seeds between the rows and under the vines. Although endemic cover crops have long been allowed to grow in vineyards, specially selected mixes weren’t commonly planted until the last decade. These special selections have an enormous influence on the structure and chemistry of the soil, helping with water infiltration and preventing the leeching of nutrients. When they’re mowed in the spring, the grasses put essential nutrients, including carbon, back into the soil.
"What we’re trying to achieve, essentially, is a natural environment for the vines," says Kirk. "Before there were vineyards in Napa Valley, this was oak grassland, a savannah really. That’s the natural state of this land and this soil, and the environment in which these soils are healthiest."
As winter arrives and the newly amended soils have been planted with their cover crops, Kirk and his crew tread lightly in the vineyards if at all. At this stage, the soils are very active biologically, and the idea is to let them "breathe" and allow the vines time to ready themselves for the next growing season. In the late winter, pruning, tying the vines, and weed control will begin…but that’s another story.
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