Everyone involved with wine stresses the importance of soil and climate on the flavour of their preferred alcoholic beverage. Yet, only a few attempt to distinguish between many types of soil. Terroir, which French scientists and viticulturists studied in-depth, comprises soil and climate. In fact, soil is as much a contributor to taste as is climate.
In regions with constant climates, vintages make little or no difference, but in those with variable weather patterns, vintage matters a great deal.
Over time, by trial and error, growers established the extreme limits of different grape varieties, and in the process determined the type of soils on which grape varieties acquire the most appealing aromas, flavours and textures.
For example, Sangiovese grown in Tuscany yields the best tasting wines, the same applies to Nebbiolo in Piedmont, particularly in Barolo and Barbaresco.
Take Pinot Noir; outside of Cote de Nuits this capricious grape rarely yields a fine wine. There are always exceptions but generally the above holds true. Who can argue the fact that the best Riesling wines come from Mosel-Saar-Ruwer and Rheingau? The list can be expanded. Some connoisseurs will argue that in New World wine producing regions many grapes thrive and yield extraordinary wines, but they are never smell and taste the same. They differ in colour, aromatics, texture, flavour and finish. All can be appealing to millions of wine consumers, but those familiar with the true characteristics of a grape always gravitate towards regions famous for their generic wines. Where else could Gamay produce the same wine as in Beaujolais in good years?
The objective here is to clarify the different soil types, and on which the best results can be obtained.
The first and foremost condition for wines to thrive is drainage. Calcareous soil and those with pebbles are known to drain water adequately. Vineyards on slopes have better drainage than those on plains. Experienced grape growers install weeping tiles in vineyards on flatlands.
Soils can be alluvial, basaltic, calcareous, clay, conglomerated, dolomite, graywacke (grauwacke), quartzite, marl, shistuous, sandy, and salty, or contain two or more of the above plus a number of dissolved minerals.
Alluvial soils consist of unconsolidated erosional gravel, sand and mud. Over time, they become consolidated.
Basaltic soils weather rapidly to good soil, but originally are fine grained crystals of feldspars (pink and white minerals found in rocks).
Calcareous means chalky or mostly chalk containing. Clay soils are fine grained and soft rock, and conglomerate soils consist of coarse-grained, poorly sorted sedimentary rock.
Dolomites are sedimentary rock with more than half calcium-magnesium carbonate.
Graywacke soils are hard, coarse-grained, sandstone of poorly sorted quartz and feldspar.
Loess is homogenous, friable, fine grained silt mixed with sand, and marl consists of limey clay, quartzite metamorphosed sand stone crystallized by hot mineralised water under pressure. Marl soils are mostly found in France.
Schistous soils contain foliated soft rock, whereas slate covered soils, prominent in the Mosel, are hard schist. Over time, schistuous soils weather and convert to excellent grape growing terrain. Interestingly, schist, sandstone, or granite are precursors of schist.
It is well known that certain grapes thrive on certain soils.
Riesling likes well-drained, sandy-clayey, loamy, agriculturally poor soils covered with slate. This is particularly the case in cool-climate growing regions, i.e Germany, Ontario in Canada, Alsace in France.
Gewurztraminer thrives on marly, deep, rich, chalky soils; whereas Pinot Gris prefers volcanic, stony or sandy, or deep rich loamy soils. Muscat family grapes grow best on sandy-loam, loamy-calcareous soils. Pinot Noir yield its best on sandy, calcareous, chalky, agriculturally poor, stony soils rich in minerals, as is the case in Cote d’Or, Burgundy, and the Willamette Valley in Oregon, U S A.
Pinot Blanc likes sandy and calcareous soils; Sylvaner loamy and light or calcareous; Cabernet Sauvignon loam with pebbles, Merlot clay mixed with loam; Chardonnay chalky, loamy with stones, Syrah well-drained loam and clay; Nebbiolo volcanic; Tempranillo clay with stones and calcareous; Sangiovese marl.
For a vineyard to produce the best quality of fruit, first both soil and climate must be analysed to determine the most suitable grape variety.
In the distant past, growers discovered the best soils, climates and most suitable grape varieties by trail and error. Later on they relied on literature, scientific observations and practical knowledge.
Generally, once a grape variety has been transplanted, the vine starts to acclimatize, as was the case with Monemvasia, which became Malvoisie in southern France, and Malmsey in Madeira. English wine merchants exporting wine from Madeira renamed Monemvasia/Malvoisie for the English market.
Muscat d’Alexandrie, originally from the eponymous city in Egypt, transplanted to France, acquired over centuries completely different aromatic and flavour characteristics. The same is true for Pinot Noir in northern Italy; Riesling in Australia, Washington State, British Columbia or Ontario; Sauvignon Blanc in New Zealand.
In addition, rootstock of which there are many, must be judiciously selected to suit the soil, vine vigour and ultimate yield objectives.
Sensitive palates can determine distinct aromatic and textural changes of the same grape grown in different terroir, which shows the sensitivity of the vine, how sophisticated vitivinculture has become, and the extent to which the palate can be honed.
Article contributed by Hrayr Berberoglu, a Professor Emeritus of Hospitality and Tourism Management specializing in Food and Beverage. Books by H. Berberoglu