Dirt Don’t Lie: The Impact of Soil on Vineyards and Wine (WineMaker)
In general, wine grapes of the Vitis vinifera family grow between the 30th and 50th parallels of latitude where the average temperatures are between 50 and 70 °F (10 and 21 °C). Grapes are grown on stony hillsides with almost no soil, the vines clinging and fighting for every inch of purchase. Grapes are grown in deep, fertile soil where they produce astounding amounts of vigor.
The most profound impact of soil on a vineyard is vigor. While soils may also impact disease (from pests, bacteria, or virus), grapeskin thickness, erosive potential, heat reflection (especially if the topsoil is stony); I will argue that vigor is the primary consideration of how dirt influences the vine, and thereby, the wine.
History
The Romans loved to conquer land and plant vineyards. From Sicily to England, the Romans enjoyed drinking wine from all over their empire — even the Roman Centurian’s staff was called the Vine Staff and was made from a thick vine stalk and used to beat lagging soldiers during marches and exercises. It was a statement — were they conquering for the Glory of Rome or for the Glory of Bacchus? The answer is both!
But back to dirt. I mention the Romans because they knew their dirt. When a new land was conquered the Romans would make quick work of establishing a system of agriculture that would yield the best results for the army, for Rome, and for the soldier that would be granted the management (and sometimes ownership) of the newly conquered farmland. The take-home message is what and where they planted.
The fertile valleys between hills and mountains tend to be very high-production and high-fertility agricultural areas. The soils tend to be deep and rich due to the alluvial action of weathered rocks and soil particles washing off the hills and mountains and being moved by water and wind into the valleys. These fertile valleys would become the grain basket for the Roman Empire — and what we would call row-crop farming was practiced in its nascent form in these fertile plains and valleys.
Moving from these high-vigor soils into the foothills that surrounded them, the Romans saw that grain, fruit, and vegetable crops failed to produce healthy yields once the soils became rocky and uneven. It was on these rocky, mixed-soil hillsides that the Romans planted olive trees, which require almost no topsoil for production, and between the olive trees, they would plant vines for wine production. A strategy that designated poorer soil for olives, and then saw that the olive trees worked to help the vines trellis themselves in the olive trees and between, initiated a style of viticultural development that changed the world of wine.
An unintended (?) side effect of putting Roman vineyards on poor, rocky soil, was that the vines struggled, grew smaller than when planted on deeper, richer soil, and produced smaller growth, smaller clusters, and smaller berries with thicker skins. Hillside and mountain-grown wines gained a reputation for quality and deep flavor, which increased the frequency of the practice of planting hillside vineyards until it became well-known to almost every vine farmer in Rome, and then in post-Roman Europe, that vines grown on inhospitable, rocky hillsides often produce very expressive wines.
On average, soil on our planet breaks down to these surprising percentages:
• 25% air (pores, or gaps in the soil)
• 25% water (obviously depending on water-holding capacity and availability)
• 45% mineral particles (inorganic: Clay, silt, and sand)
• 5% organic matter of which there is:
– 80% humus (plant matter broken down by insects, bacteria, etc.)
– 10% plant roots
– 10% soil organisms (such as bacteria, insects, worms, nematodes, etc.)
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