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GSA TODAY | MAY 2016 group of vineyards (Chehalem Wines, 2015) and (2) yield of
Oregon Pinot Noir from the National Agricultural Statistics
Service (2015). Terroir pH thus is most strongly expressed in
vintages when there are a lot of grapes, perhaps because wine-
makers impose fewer interventions.
OTHER DETERMINANTS OF WINE QUALITY
The 2009 vintage was excellent (86 points), like that of 2010
(88 points), but not exceptional like 2008 (94 points), as ranked
by wine industry appointed connoisseurs (Parker, 2015, who did
not rank 2011). Thus, the years of good soil pH expression in
wines were not necessarily years of acclaimed and highly profit-
able wines. The acclaimed vintages show a very clear relationship
with lack of precipitation in October (Fig. 4C), one of the reasons
why wine production is so successful in regions with dry summer
(Mediterranean) climates (Goode, 2014). No correlation was
found between mean annual precipitation and either the size of
the harvest or quality of the wine vintage.
CONCLUSIONS
This study supports with data two traditional tenets of vineyard
management: (1) “treat vines mean to keep them keen,” and
(2) “deep-rooted vines better express terroir” (Goode, 2014). By
these epigrams, vintners mean keen in the sense of more flavorful,
and terroir in the sense of soil-related differences. One hardship
for vines is lack of moisture before harvest, which is related closely
to the quality of vintages (Fig. 4C). Another handicap to vine
vigor is low soil pH, and thus fewer mineral nutrients, which has
the effect of raising wine pH (Fig. 3A). It is the pH minima of the
deep levels of soils in Oregon that appear to most affect both
grape and wine pH (Fig. 3B). These stresses may induce vines to
invest in future propagation rather than vegetative growth, by
producing more fruit than leaves, and within the grapes, less
organic acid, and more cations (Ca2+, Mg2+, K+, Na+) and flavor,
color, or aroma compounds to attract dispersers (Goode, 2014).
These organic compounds are complex and beyond the scope of
this study (Fang and Qian, 2005), so our study does not address
the fruit versus spice flavors of Willamette Valley wine (Burns,
2012), nor perceived “slaty” or “earthy” flavors in wine (Maltman,
2008). Nevertheless, pH is also an important element of the taste
of wine. High pH (3.7–4.0) Pinot Noir wines with rounded and
complex flavor are produced on low-pH, deep, middle Pleistocene
soils, such as the Jory Series. Low pH (3.3–3.7) Pinot Noir wines
with brisk and less complex flavor are produced on high-pH,
shallow, late Pleistocene to Holocene soils, such as the Hazelair
Series. Soil age and nutrient status has also been noted as a factor
in wine quality in other regions (Costantini et al., 2012). Soils
have a significant effect on the pH and taste of both grapes and
wine, but these effects are increasingly obscured by blending and
other winemaking techniques (Goode, 2014).
We conclude that one can taste some aspects of soil in wine,
especially acidity. For Pinot Noir wines of our region, astringent
taste tending toward vinegar comes from vines overfed by fertile
Holocene soils, but rounded and buttery taste comes from vines
that struggled in infertile mid-Pleistocene soils. However, acidic
wines from young soils are less prone to spoilage than less acidic
wines from old soils. Wine, like soil, is a living medium with a
geological heritage.
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ACKNOWLEDGMENTS
Erick Bestland, Bruce Runnegar, Ronnie LaCroute, and
Joshua Roering offered useful discussion. Marli Miller generously
allowed use of Fig. 2B. The cover photo was contributed by
Matt Boyington of Willamette Valley Vineyards. Perceptive
reviews from Alex Maltman and Jerry Dickens greatly improved
the manuscript.
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