Grapevines grow just fine in water supplemented with a few nutrients, a method known as hydroponics. Growing hydroponically has lots of advantages. Because it can be done indoors, hydroponics allows perfect temperature control, and it avoids disease pressure often associated with rain, humidity, and insects. Vegetative growth can easily be regulated by adjusting the amount of carbon dioxide in the atmosphere and the amount of nitrogen in the aqueous solution. It’s little wonder that tomatoes, lettuce and other vegetables, and most commercial marijuana are grown hydroponically.
But many wine growers stubbornly cling to ancient notions of terroir, the idea that the place in which the fruit is grown has a major influence on the taste of the final product. These “terroirists” view themselves as interpreters of their vineyards and not as creators of a wine. They view wines that express the characteristics of the vineyard, such as the minerality often seen in cool climates with limestone derived soils, as ambassadors of “place,” and by association, the vineyard, the farm, and the surrounding community.
There are several ways in which soil can affect the way that wine tastes. The first, and probably the most important, is the movement, distribution, and purity of water in the soil. The amount of water available to plants is determined by the soil’s slope, texture, rock and organic matter content, and depth. Vines in areas with too much water available to them tend to grow vigorously, using energy to produce more foliage than is optimal to ripen the fruit. Indeed, wine grapes tend to do best in conditions of modest water deficit during ripening, and it’s this characteristic that has resulted in the aphorism that vines must “struggle” to produce the best wine.
Soil mineral content plays a substantial role in shaping the characteristics of wine. Minerals in soil largely come from weathering rocks, but they have a much more ancient origin, forming just a few million years after the Big Bang. Most of the earth’s 4,500 known minerals are composed of combinations of just six elements – oxygen, silica, aluminum, calcium, magnesium, and iron. For the most part, the effects of minerals on wine are indirect. For example, in wet conditions, orthoclase feldspar (composed of silica, oxygen, and potassium) is converted to kaolinite clay, releasing potassium that is taken up by vines and transported to the berries. During fermentation, high levels of potassium can precipitate tartrates and reduce acid levels, giving wine a flat, flabby taste. On the other hand, high levels of dolomite (an oxide of calcium and magnesium) compete with potassium uptake, thus increasing wine acids, and it is associated with thick skins, resulting in resistance to infection and more intense flavor in the wine.
Finally, living organisms in soil directly and indirectly influence the characteristics of wine. Microbes – bacteria, yeasts, fungi – provide nutrients in digestible forms to the vines, and they compete with plant pathogens. They digest dead plants and animals to form organic matter that acts as a store for nutrients and water. Many microbes make their way into the fermentation tanks, altering fermentation kinetics and the flavors that result. Larger organisms, such as insects and worms, modify soil structure, allowing better drainage and oxygenation that promote vine health and ripe fruit. Together with the other components of soil, living organisms help to form a dynamic, complex ecosystem that is constantly changing and renewing itself.
Those of you who have toured with us know the effort that we’ve made to understand Dodon’s soil and its origins, the care we’ve taken to select the most appropriate varieties and rootstocks, and the attention we’ve paid to laying out the vineyard to best match the plants with the underlying soil. Despite
the potential of hydroponics to make consistently good wine, we’ve chosen the more difficult, potentially more costly traditional methods because we believe that soil plays an essential role in crafting wines of depth, harmony, and balance that reflect the place in which they were grown. In subsequent posts, I’ll describe the story of Dodon soils, where they come from, what they are, and how they make Dodon wines.