The terroir of Pinot noir wine in the Willamette valley, Oregon – a broad analysis of vineyard soils, grape juice and wine chemistry

Wine-grapes in the Willamette Valley, Oregon, are grown on three major soil parent materials: volcanic, marine sediments, and loess/volcanic. This study examines differences in the soil properties and elemental chemistry of the soil parent materials at various vineyards to document their effect on wine chemistry. The physical characteristics of soils from all the three parent materials indicate: they are old (>50,000 years) based on their high clay content, low cation exchange capacity, red colors, and high Fe and Al content. In my study region, volcanic and marine sediment soils are more developed with slightly lower acidity than the loess/volcanic soils. A new finding for this region is the presence of pisolites (Fe/Mg concretions) in the volcanic and the loess/volcanic soils, but absent in the marine sediment soils. Volcanic soils have the highest P, S, Fe, Co, Mn, and V concentrations and the lowest As and Sr values.

Marine sediment soils have higher Cl and Sr and lower P, Co, Mn, Ba, and V concentrations than volcanic soils. Loess soils have the highest values of K and Mg and are similar to volcanic soils with higher P and V values and similar to marine sediment soils with higher Sr values. The main elements found to be significant in determining one parent material from another are V and Mn (volcanic soils), Mg and K (loess soils), and Sr (marine sediment or loess soils). Sr is slightly higher in grape juice and wine from vines grown on marine sediment parent material compared to volcanic and loess parent material, whereas Mn is higher in the juice and wine from grapes grown in volcanic parent material. P, S, Fe, Co, V, Cl, Ba, Mg, and K did not maintain their relative concentration levels from soil to grape juice to wine. The principal component analysis shows that soil and wine chemistry differs between parent material, but is inconclusive for grape juice chemistry.

Authors: Kathryn Nora Barnard (1), Scott F. Burns (1)

(1) Department of Geology, Portland State University, 1825 SW Broadway Avenue, Portland, Oregon., USA


Keywords: Pinot Noir, ICP-MS/AES, particle size, cation exchange capacity, X-ray fluorescence, clay mineralogy, grape juice chemistry, wine chemistry, soil chemistry

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