You often hear at tastings that a German Riesling tastes like local slate, and in Chablis you can taste the chalky notes characteristic of Chablis soils. Modern science says that the “minerality” we taste is not dissolved minerals transferring from the soil to the wine.
“The proportion of mineral nutrients in the finished wine has only a complex, indirect and remote relationship to the geological minerals in the vineyard,” says Oxford University professor Alex Maltman in his 2018 book Vineyards, Rocks & Soils.
Soils affect how the vine was nourished, how the grapes ripened, what they are nourished with and, consequently, what the resulting compounds are converted into.
So what types of soils do sommeliers like to talk about?
Clay soils
Soils with the finest particles – shallower than silt and sand – so they retain water well and maintain cool temperatures. This is especially useful in vineyards in hot, dry climates. Clay soils tend to be rich in nitrogen, potassium and phosphorus, which the vine converts into the compounds it needs to live.
Clay soils have poor drainage, so vineyards can become waterlogged. Clay is heavy and requires a lot of labor. The wines are full-bodied, rich. The wines are full-bodied and rich.
Regions: Napa, Bordeaux, Rioja and Ribera del Duero, Von Romanée.
Slate
The dark shades of slate make it a good conductor of heat and its appearance promotes drainage, which is very useful in climates prone to rain. Slate also reduces soil erosion. On the other hand, the structure of slate soils makes the vines “work” more for water. The wines are complex, mineral wines.
Famous regions with slate soils: Moselle, Priorat, Alsace, Languedoc, Loire and Rhone valleys, the Douro Valley
Sandy soils
Very porous soils through which water can easily pass.
Drained soils are good for vines, but can lead to drought stress if the root of the young vine does not have access to water reserves. Vines on sandy soils are resistant to phylloxera. Sand is low in organic matter, so many grape growers use compost or humus from plant cover crops.
The wines are non-expressive, light, elegant.
Regions: northern Medoc and Grave in Bordeaux in France, Dao, Setubal, Colares in Portugal, the Bethany area in the Barossa Valley and Blewitt Springs in McLaren Vale in Australia, the Franshoek Valley in South Africa.
Granite
Composition and texture vary with location. Water seeps quickly into rocky soils and roots have to grow deep to extract moisture. Vineyards are cleared of other plants that compete for water. Deep roots make the vines more resistant to extreme drought conditions. Granite soils are said to be twice as much work and half the yield compared to lime soil. Wines from granitic soils have a higher pH, favoring high acidity. Powerful, structural, expressive.
Regions with granite soils are Beaujolais, Northern Rhône, Alsace, Corsica, Sardinia, Maldonado in Uruguay.
Limestone
Contains many nutrients for the vine, but causes iron deficiency in the grapes, so it is fertilized. Limestone retains moisture in dry weather and provides good drainage. The wines are elegant, with good acidity.
Regions: Champagne, Chablis, Pouilly, Sancerre, Southern Rhône in France, Paso Robles in California in the USA.
Volcanic soils
Very diverse because they are formed from volcanic material ranging from coal-black lava basalts to fragments ejected from the mouth of a volcano. Generally porous and provide good drainage, which makes the vines grow deep. The wines are fine, elegant, mineral, often with a smoky note and good acidity.
Popular regions: Etna in Sicily and Vesuvius in Campania, Santorini in Greece, Canary Islands, Napa in the USA.
