What Is the Impact of Soil on Wine?

Scroll the table sideways to see every column

Soil sets how much water reaches the roots. In a Bordeaux study of Merlot, Cabernet Sauvignon and Cabernet Franc on gravel, heavy clay and sand, climate and soil mattered more than the grape variety, and the authors tied both to vine water status.

A mild water shortage keeps berries small and raises anthocyanins, the pigments that color red wine. A severe one stops ripening. Top red wines tend to come from vines of moderate vigor, held back by mild water stress or low nitrogen. Shallow or stony soils in moderately dry climates give these conditions most often.

Soil also sets warmth. Dark, stony soils warm fast and bring ripening forward. Pale, chalky soils reflect light and slow heat build-up, which helps grapes keep their acidity.

Nutrients matter too. Potassium, common in clay soils, raises the pH of the juice and softens its acidity. On high-pH limestone sites, vines can struggle to take up iron and magnesium, which yellows the leaves (chlorosis) unless the rootstock suits the site.

Texture is the share of sand, silt and clay in a soil. Sand has the largest particles and drains fastest. Clay has the smallest and holds the most water and nutrients.

Parent rock such as limestone, granite, basalt or schist weathers into these particles. Water, wind, glaciers and volcanoes move them and lay them down again as loess, alluvium, colluvium or volcanic ash.

Soil pH controls which nutrients dissolve and which microbes live in the soil. Clay and organic matter hold potassium, magnesium and calcium and release them to the roots.

Limestone and chalk are rock rich in calcium carbonate. Marl is limestone mixed with clay.

These soils are pale and cool. They reflect light and slow heat build-up, which helps grapes keep their acidity.

Chablis grows Chardonnay on Kimmeridgian limestone and marl full of fossil oyster shells. Champagne sits on Cretaceous chalk, which drains well and stores water the roots can reach. In Barolo, the Tortonian marls of La Morra and Barolo give more perfumed wines than the sandstones of Serralunga and Monforte.

Clay has the finest soil particles, packed close together.

It holds water and nutrients, which pushes vine growth and yields up. Many clays are high in potassium, which raises the pH of the juice and softens its acidity.

Pomerol and Fronsac, on Bordeaux's Right Bank, grow Merlot on clay and limestone.

Sand has coarse particles with wide gaps between them.

It warms and drains fast and holds little water. Reds from sand are often perfumed and light in tannin.

Parts of Chianti Classico and Tokaj have sandy vineyards.

Gravel is rounded stones and pebbles laid down by rivers.

It drains well, and the stones hold heat.

The Médoc grows Cabernet Sauvignon on gravel terraces along the Garonne. Châteauneuf-du-Pape has large rolled stones called galets.

Slate and schist are layered rocks that split into flat plates.

They make shallow, dark soils that store heat and hold back vine growth.

The Mosel's steep slopes are Devonian slate, planted to Riesling that is light in body and high in acid. Priorat's llicorella is crumbled slate with quartz, planted to Garnacha and Carinyena. The Douro is schist.

Granite is hard rock that weathers into coarse, acidic sand.

The ten Beaujolais crus, from Fleurie to Moulin-à-Vent, grow Gamay on decomposed granite with thin topsoil. Gamay from these sites is often floral, with fine tannin.

Granite also shows up in pockets of the northern Rhône.

Volcanic soils come from basalt, lava, pumice, tuff and ash. They are porous and rich in minerals.

Etna grows Nerello Mascalese and Carricante on basalt sands and lava flows of different ages. Santorini grows Assyrtiko on pumice, tuff and ash, with extreme drainage.

Soave has basalt next to limestone, and the Canary Islands also farm volcanic soils.

Loess is fine silt carried and dropped by the wind.

It is deep and even, so vine roots can grow deep.

The Wachau and Kamptal in Austria have loess terraces. Oregon's Willamette Valley has loess soils called Laurelwood, next to volcanic Jory and marine Willakenzie soils.

Alluvium is soil carried by rivers. Colluvium is soil moved downhill by gravity.

Both are a mix of silt, sand and stones that changes within a single vineyard. Drainage depends on how deep the soil is and how many stones it holds.

Napa Valley has alluvial soils on its valley floor and fans, next to volcanic hills and marine sediments.

Vines take up potassium, calcium and magnesium as ions dissolved in the water in the soil. Rock minerals such as quartz and feldspar do not dissolve, and the mineral content of wine sits far below what people can taste.

Tasters still describe some wines as mineral, and experts do not agree on what the word means. The minerality guide covers what studies have found.

Grapes from high-potassium clay soils give juice with a higher pH, which makes sulfur dioxide less effective. Winemakers adjust sulfite additions and oxygen exposure to match.

Grapes from cool limestone sites keep more acidity, which shapes decisions about malolactic fermentation and time on the lees. Grapes from poor, rocky soils can be low in the nitrogen yeast need, which risks slow fermentations and hydrogen sulfide.

Cover crops add organic matter, help water soak in, feed the fungi around the roots and hold back vine vigor. Less tilling and more compost protect soil structure and reduce erosion, which matters most on slopes, where terraces and mulch also hold thin, stony soils in place.

Growers match rootstock and planting density to the soil's pH, vigor, salinity and drought risk.

Can you taste the soil in wine?

No. Vines take up nutrients dissolved in water, not rock. Soil changes how the vine grows, through water, warmth and nutrients, and that changes the grapes.

Which soil is best for wine?

None on its own. Climate, grape variety, rootstock and farming all interact with the soil. Top red wines tend to come from vines held back by mild water stress, most often on shallow or stony soils in moderately dry climates.

Why does limestone matter for white wine?

Limestone and chalk soils are pale and cool. They slow heat build-up, which helps grapes keep their acidity. Chablis and Champagne both grow on them.

What is the difference between alluvium and colluvium?

Alluvium is soil carried and dropped by rivers. Colluvium is soil moved downhill by gravity. Both mix silt, sand and stones.

Why does soil pH matter?

Soil pH controls which nutrients the vine can take up. High-potassium soils raise the pH of the juice, which affects how fresh the wine tastes, how stable its color is and how well sulfur dioxide works.

• van Leeuwen et al. (2004): Influence of climate, soil, and cultivar on terroir, AJEV
• van Leeuwen et al. (2009): Vine water status is a key factor in grape ripening, OENO One
• van Leeuwen and Seguin (2006): The concept of terroir in viticulture, Journal of Wine Research
• Maltman (2013): Minerality in wine, a geological perspective, Journal of Wine Research

Drawings made from photos on Wikimedia Commons by Marek Ślusarczyk (Tupungato), Olivier Letourneux, Pascal3012, Repuli, Anthony Baratier, Rolf Kranz, Mpmpmp, LBM1948, muppetspanker, John Morgan (CC BY 2.0, CC BY 3.0, CC BY-SA 2.0, 3.0 and 4.0). Each photo is credited and linked under its drawing.