TERROIR OF THE HELVETIA WINERY, WASHINGTON COUNTY, OREGON: THE INFLUENCE OF FRAGIPANS AND PISOLITES

The soils at Helvetia Winery, located at 45^o36’54” N latitude and 122^o54’19 W longitude in the northern part of the Tualatin Valley, an extension of the Willamette Valley, 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 deposited throughout the last glacial period. In the main Pinot Noir vineyard 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 deeper in depth allowing the soil to drain better and grape roots to extend further in the subsurface. The fragipan is encountered in the upper area at 60 cm depth in contrast to the lower catena pits of the main vineyard at 33-38 cm depth. A nearby Chardonnay vineyard is found on an ancient landslide and contains better drainage than the Pinot Noir vineyard because of lack of a fragipan. Both 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 to their iron content. The pisolites that develop from weathering of the loess are the foremost soil characteristic that distinguishes the terroir of this vineyard.