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The Dirt on Vineyard Soil

Erin O'Reilly - Certified Specialist of Wine

If you pick up a crumbling fistful of vineyard soil, you’ll hold in your hand a complex set of ingredients to make great wine.

But before getting into how...

dead grapes in the vineyard soil

What Exactly Is Soil?

Soil is a combination of solids (organic and inorganic material), liquids and gasses. It occupies a physical space and supports rooted plants in an environment. With only about 12% of the Earth’s surface available for cropland, researchers have long studied how to maximize the land’s productivity. Viticulturalists are no exception.

Soil quality and soil function are interrelated.

Dirt stores water and nutrients for plants, but not all soils act the same way. The properties of a desert floor logically vary from those of a fertile plain. As soil develops, its characteristics depend more heavily on environmental factors (e.g., temperature and precipitation).

Testing Vineyard Soil.

Viticulturalists run soil analyses for each of their vineyard blocks. Vineyard soil analyses break out the soil’s composition; physical properties include texture (particle size), structure, density (compaction), water holding capacity, organic matter content, and even color.

Knowing a soil’s properties guides viticultural decisions.

For example, water holding capacity is a combination of soil texture, structure, and organic matter. An analysis provides the percentage breakdown of sand, silt, and clay to give a picture of the overall texture. The sandier a soil is, the less water holding capacity it has. Conversely, vineyards with more clay are better at retaining water. Soil structure can indicate the amount of water that will drain off vice be retained near the vine roots after rainfall or irrigation.

Texture also regulates soil temperature. Damp, clay soils warm up more slowly in marginal growing climates (e.g., Finger Lakes, NY). Viticulturalists will stay away from early budding varieties, like Chardonnay and Pinot Noir, if the soils are too slow to warm up in the spring when the vines begin to bud.

vineyard with orange soil

Even soil color plays a role in vine growth.

Dark soils absorb radiant heat during the day and release it overnight. Soils with large stones or pebbles act the same way. Heat released overnight can help berry development in cooler growing climates. Conversely, light soils, like the chalky soils of Champagne, reflect solar energy to the undersides of the canopy, exposing more leaf surface area to photosynthesis for vine growth, a helpful characteristic in cool or cloudy growing regions.

Vineyard Soil pH.

Soil pH is as important as wine pH. Viticulturalists test soil pH by creating a slurry mixture. Soil pH determines how accessible different nutrients are to the vine for uptake. Testing soil pH along with nutrient analyses will tell the vineyard owner what supplemental fertilizer the land needs in specific quantities.

What’s the best soil for wine?

There’s no easy answer. Each vineyard’s soil profile is unique and translates directly into the style and quality of wine crafted from the land. The best soil for wine is one that provides the optimal levels of nutrients and water to balance vine growth and berry development for the particular variety planted in a specific region.

And like so many things in wine and life in general, vineyard soil is about finding that perfect balance.

Erin O'Reilly Author Bio Image Author Bio: Erin O’Reilly, Certified Specialist of Wine, is a wine writer and educator. She pens her work from Monterey wine country where she raises a glass to the growers and producers dedicated to crafting great wines.