CHARACTERIZATION OF FRAGIPAN SOILS AT HELVETIA WINERY, WASHINGTON COUNTY, OREGON

The soils at Helvetia Winery, located 45 degrees 36' 54” N. Latitude, 122 degrees 54' 19” W. Longitude in the northwest section of the Willamette Valley, Oregon, are Humic Fragixerepts, characterized by silt deposits that contain a dense, low permeability fragipan layer. They have developed in 15,000 year old loess deposits (wind-blown silt). In the main vineyard of Pinot Noir grapes there are two distinct slope surfaces: The lower portion is a 28% slope and the upper portion is a 19% slope. The slope break occurs approximately at 541 feet elevation. The upper slope is a more desirable grape producing area because of the superior drainage. In the upper slope the fragipan is found at a deeper depth allowing the soil to drain better and the grape roots to extend further into the subsurface. The Chardonnay vineyard found in the landslide deposits contains better drainage than the lower and upper portion in the main vineyard plus it also contains a buried A-horizon. The fragipan in this area is not encountered until 60 cm in contrast to the lower catena pits of the main vineyard which are at 33 to 38 cm. Both the Pinot Noir and Chardonnay vineyards contain abundant pisolites (iron concretions) throughout the soil profile. The presence of pisolites is favorable to the winery because they add rich, cherry flavors to the wine due of their iron content. The pisolitic structures that develop from weathering of the loess are the foremost soil characteristic that distinguishes the terroir of the vineyard.