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Figure 2. Red Jory Ultisol of Willamette Estate Vineyards in the south Salem Hills, Oregon, USA, where it is developed atop a thick middle-Miocene Oxisol
                      (lateritic bauxite), red in the vineyards (A), and thick in a nearby quarry (B). The Jory soil series is intensely planted in vines, but comes in two distinct varieties
                      parented by bauxite or by basalt. Photo A courtesy of Matt Boyington; photo B courtesy of Marli Miller.

GSA TODAY | MAY 2016  than harvest date (vine age, plant spacing, trellising, rootstocks,   relationship was found between wine pH and the depth to the
                      fertilization, canopy management) and of viniculture other            base of the clayey (Bw or Bt) horizon in the soil (Fig. 3B). These
                      than blending (crush methods, destemming, sulphite and                relationships have a common cause with soil age, because in
                      acid addition).                                                       Oregon, as elsewhere, pH declines and soil depth increases as soils
                                                                                            develop through time (Lindeburg et al., 2013). Among the soils
                        Other data compilations used in this study were precipitation       studied, there is a significant negative correlation between
                      records from 1999 to 2012 for Rex Station near Newberg (National      minimum soil pH and depth to the base of the clayey horizon
                      Oceanographic and Atmospheric Administration, 2015),                  (Fig. 3C). All these relationships are significant at greater than
                      Oregon vineyard harvest reports (National Agricultural Statistics     99% confidence determined by an ANOVA F test, because more
                      Service, 2015), and Chehalem Vineyard harvest reports                 than 20 wines are included within each series.
                      (Chehalem Wines, 2015).
                                                                                              Within the data assembled, wine pH showed no relation with
                      SOIL DETERMINANTS OF WINE ACIDITY                                     maximum soil pH, perhaps confounded by different practices of
                                                                                            mulching, cover crop, or fallow at the surface. Wine pH correlated
                        The main result of this study is discovery of an inverse relation-  with neither minimum nor maximum soil clay content, nor
                      ship between the pH of wine and the minimum pH of the soil in         minimum nor maximum cation exchange capacity, again perhaps
                      which it is grown (Fig. 3A). A comparable but direct (not inverse)

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