RT Journal Article SR Electronic T1 The Use of Soils for the Delineation of Viticultural Zones in the Four Corners Region JF American Journal of Enology and Viticulture JO Am J Enol Vitic. FD American Society for Enology and Viticulture SP 290 OP 296 DO 10.5344/ajev.1981.32.4.290 VO 32 IS 4 A1 Gordon R. Dutt A1 Eugene A. Mielke A1 Wade H. Wolfe YR 1981 UL http://www.ajevonline.org/content/32/4/290.abstract AB Delineation of viticultural zones has been useful in making varietal recommendations and predicting wine quality. The California base 50 growing-degree-day model fails to predict zones in the Four Corners Region which are comparable to California, either in adaptable varieties, sugar and acid or color of red varieties. A new model has been developed based on modern soil surveys and altitude. The soil parameter most useful in describing viticultural adaptability is the mean annual soil temperature at 50 cm. This parameter subdivides soils into hyperthermic, thermic and messic. Most wine grapes in California are produced on thermic soils, hence, this soil group has been subdivided. Altitude (inter-related to temperature) is the secondary parameter. Zones defined are HT (hypothermic), T1 (low-level thermic), Tm (mid-level thermic), Th (high-level thermic), and M (messic). This system while encompassing the G.D.D. concept, allows for wider climatic conditions to be considered.