THE GREAT DEBATE IN OREGON: WHICH SOIL PRODUCES THE BEST PINOT NOIR IN THE NORTHERN WILLAMETTE VALLEY

Terroir, the relationship of geology, soils and climate to the quality of wines, is so important to winemakers. They want to make sure they have the best soil possible to produce the best wines. In a completely updated study of over 300 vineyards in the northern Willamette Valley, the heart of the winemaking area of Oregon, two soil series are the dominant varieties of the wineries, but four other soils have also shown great promise. The two dominant soils are the Jory, an Ultisol developed on 15 million year old basalt bedrock, and the Willakenzie, an Alfisol developed on marine sedimentary rocks of the Coast Range. Both are very old (over 50,000 years old), well drained, on side slopes, xeric moisture regime, and red. Alfisols have a few more nutrients in them than Ultisols. Four other soils with similar features are also being planted on with good results. Laurelwood soil is an Alfisol developed on mainly basalt with some old loess mixed in. Nekia is very similar to Jory (an Ultisol on basalt), but it is shallow (from 50-100 cm depth) compared to the Jory. The Yamhill series is developed on basalt, but it is not as old and is mainly a Mollisol with a thick A horizon. The Cornelius soil is also an Alfisol but is developed in old loess deposits. Four other soils were noted to be not as good for wine grapes: Peavine because it does not have a xeric moisture regime; Woodburn, Amity, and Dayton because they are not as well drained and they have too many nutrients because they are on the valley floor developing in Missoula Flood deposits. Our study shows that for the best terroir the best soils for producing great wines in Oregon are old, well drained, xeric moisture regime, and red.