Vineyard Soils
The soil composition of vineyards is one of the most important viticultural considerations when planting grape vines.
The soil supports the root structure and influences everything important for grapevine health and grape quality:
- Water drainage and water retention
- Water and Nutrient availability
- Vine stress and root development
- Heat assumption and heat retention
The ideal soil condition for a vine is a layer of thin topsoil and subsoil that sufficiently retains water but also has good drainage so that the roots do not become overly saturated.
The ability of the soil to retain heat and/or reflect it back up to the vine is also an important consideration that affects the ripening of the grapes.
Flavor Influence
Each type of soil has unique properties that can influence the flavor, aroma, and overall quality of the wine. Winemakers often choose grape varieties that are best suited to the specific soil types in their vineyards to produce the best possible wines.
Different soils provide us with the different regions and areas that produce the world most famous wines.
It is also important to know that soil can be different across wine-growing regions. It can even be different across a single vineyard.
Vineyard Drainage
Vines that must dig deep for water are the most resilient.
These vines are producing better fruits in both dry and wet seasons.
Soil Composition
Most vineyards are a blend of stones, gravel, top soil and deep soil.
Alongside climate and grape selection, vineyard soils play a crucial role in the quality and characteristics of wines.
Clay
Clay have fine particles and is known to hold water longest of all soil types.
Clay holds onto nutrients effectively, and due to the water retention, clay is less susceptible to drought.
Clay may be prone to compaction, can be challenging for root penetration, and may require soil management practices like aeration.
Loam
Loam is a combination of Sand, Silt and Clay.
Loam is considered the best soil for almost any type of plants:
- It is granular
- It retains water
- It have good drainage
- It contains organic matter
Loam can be too fertile for vine grapes that need more difficult soil to struggle with.
Silt
Silt is found in River Valleys.
It is a granular material of mineral particles smaller than sand and larger than clay.
Silt is more fertile than sand, hold moisture well, but is prone to compaction (similar to clay), which can affect drainage and aeration. With proper management, silty soils can be suitable for vine cultivation.
Loess
Loess is a sediment of accumulated wind-blown dust of sand and silt cemented by clay and lime.
It is defined as 20% clay with roughly 40% sand and 40% silt.
Loess is pronounced luss and means "loose". It is commonly known as "brickearth" in the UK.
Loess is porous and permeable, great for root penetration, and full of nutrients giving minerality to the vines. It is very fertile and has good water retention and warming properties, but drains poorly.
Sand
Sand is found near large bodies of water, like in coastal regions and river valleys.
It is a granular material of mineral particles bigger than silt. It can come from any type of rock that has been broken down into small grains.
Spiaggia Grande vineyard in Sardinia (Italy) on a sandy soil close to the sea.
Sandy soils warm up quickly in the spring, aiding early vine growth. They have good drainage, but can dry out quickly and struggle with water retention. In regions with little rain, sandy soils may require more irrigation.
Sandy soils are one of the few soils that Phylloxera does not thrive in.
Limestone
Limestone are sediments of calcium carbonates from organic matter like fossils and shells.
Gravel
Gravel soil is pebble soil that has good drainage but poor fertility.
Plants in gravel soil must penetrate deeply to find nutrients in the subsoil.
Wine from clay subsoil have less acidity than those from limestone subsoil.
Gravel Soil of the Bordeaux wine estate Chateau d'Yquem
Granite Soil
Granite soils are sandy results of the decomposition of granitic rocks.
Formed from magma, granite soils have a high content of silica (quartz) and many other minerals.
Granite soil is often loose, with a sandy clay structure. This allows gentle ripening. During the day they radiate heat. During the night they cool down quickly.
This temperature difference allows the sugar values to increase with sunlight and prevents acidity loss at night.
Slate Soil
Slate is a metamorphic, plate-like rock formed when shale, clay, or siltstone is subjected to pressure deep within the earth.
When you see the Licorella slates of Priorat in Spain, you wonder how anything can grow here.
Slate soil retains heat well and warms up relatively quickly. It absorbs and reflects heat that helps to ripen grapes.
Schist Soil
Schist is a hard, crystalline rock narder than slate. It has layers of minerals that can flake off easily.
Schist soil at Clemens Busch in the Mosel
Schist retains heat well and produces powerful wines with rich minerality.
Rolled Pebbles
Galets Roulés (Rolled Pebbles) soils have larger, rounded, smooth stones, polished by the water in a river.
Volcanic Soils
Volcanic soils are formed from volcanic ash and lava stones broken down (from weathering) to soil. They are rich in iron and other minerals, and they have excellent drainage as well as good heat and water retention.
Volcanic soils can impact unique flavors and aromas to wine.