Soil Characteristics
There are some general soil characteristics that all high quality vines enjoy. The major variables are soil depth, soil fertility, mineral content, soil color, soil drainage, heat retention, soil acidity, and cation exchange capacity.
Soil Depth
Most noteworthy wines are produced with grapes grown in deep, well drained soils. Low fertility and distinctive minerality are also a plus. Soil depth determines how deep a vine’s roots can grow. Vines will not grow in gray, unporous subsoil.
Soil Fertility
Contrary to most crops, the best grapes come from vineyards with low soil fertility. Poor soil produces small yields of grapes with concentrated flavors. Overly fertile soils lead to overgrown vines that must be pruned. This has led to the saying, “To produce great wine, the vine must suffer.”
Mineral Content
Vineyards with the right mineral content produce grapes with complex, nuanced flavors and aromas. Although there is significant disagreement about how much soil minerality directly affects how a wine tastes, it certainly affects decisions in the vineyard.
Soil Color
Soil color is one of the most telling aspects of a vineyard. If the subsoil is a lighter color, including tan, red or brown, it means that the soil is porous, well drained and has little organic material. Quality grapes are produced in these geologic conditions. Red and orange indicates the soil has oxidized iron in it. Grey soils drain poorly, contain a lot of organic material, and are not suitable for grapevines.
Soil Drainage
Soil Drainage is another important characteristic of a vineyard site. Grapevines are ideally planted in soils that are not compacted and that drain well. This induces a vine’s roots to grow deep into the ground in search of water pockets. A vineyard with deep roots is less susceptible to changing weather patterns.
Heat Retention
The heat retention of soil can affect vineyards by continuing to ripen grapes after the sun sets. The larger the soil’s particle size, the better it retains heat. Therefore, clay soil retains less heat than sand, silt and loam. Fuller bodied varietals that require a lot of heat to ripen thrive in soils that retain heat well.
Soil Acidity
Soil Acidity affects which varietals are planted in a particular vineyard. High acid grapes have traditionally been planted in high pH soils, and low acid grapes often do best in soils with a low pH.
Cation Exchange Capacity
The Cation Exchange Capacity (CEC) of a soil is one of the key characteristics that determines its nutrient content and availability. In many ways, the quality of a soil is indicated by its ability to do cation exchange.
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