Monday, November 13, 2006

Site Assessment of the Wawawai Canyon Vineyard.

Suphasuk Pradubsuk1, Erik Smith2, and Christine Havens2. (1) Dept of Crop and Soil Sciences, Washington State Univ, N Bunn Rd, Prosser, WA 99350, (2) Dept of Horticulture and Landscape Architecture, Washington State Univ, N Bunn Rd, Prosser, WA 99350

Site assessment of the Wawawai Canyon vineyard, WA was conducted to investigate its capabilities, unique qualities, and deficiencies. The study area comprised of three zones-a 10 year-old main vineyard, a 2 year-old vineyard, and a field site prepared for a new vineyard, all of which are on south facing slopes. Soil samples, collected according to landscape features, were analyzed for physical and chemical properties. The vineyard’s capacity was evaluated from field observation, laboratory analysis of collected soil samples and consideration of larger scale data on climate, hydrology and geology.  The study found that the 10 year-old main vineyard appeared to have variation in soil textures (silt loam and loam), soil depth (50-77 cm), and distribution of calcium carbonate content.  This may have contributed to imbalanced grape vigor due to areas of both higher and lower plant nutrient availability in addition to an overall site sensitivity to short term changes in soil moisture. Soil uniformity, or the lack thereof, should be taken in consideration for soil preparation, varietal selection and canopy management practices to achieve high quality grape production. The field site on the southern portion of this area had a moderate capacity to produce fine grapes associated with soil depth (67-83 cm), variable texture (silt loam and sandy loam) and being in the footslope position. Conversely, the 2 year-old vineyard on the eastern portion of the area had the highest capacity associated with the same soil depth (68-83 cm), uniform soil texture (loam) and south facing slope position. Variation of soil texture among the three sites confirms the geologic history of this area as the site close to the Channeled Scablands, where soil formation was mainly influenced by Quaternary glacial sediments and wind blown loess.