Issue link: http://winesandvines.uberflip.com/i/816747
24 WINES&VINES May 2017 WINE INDUSTRY NEWS Y ountville, Calif.—The practice of irrigat- ing with wastewater was covered during a recent program in Napa Valley that included visiting specialists from the Depart- ment of Viticulture and Enology at the Univer- sity of California, Davis. According to two speakers who dug into the topic, preliminary studies show no significant vineyard degradation as a result of using at least some treated wastewater in irrigation. UC Davis enology extension specialist Anita Ober- holster presented grape and wine findings in- cluding recent trials conducted by herself, David Hirzel, Kerri Steenwerth and Sanjai Parikh. Though it's somewhat controversial, Ober- holster reminded attendees that irrigating with winery wastewater can be beneficial. It can provide organic matter and nutrients including nitrogen, phosphorus and potassium. And added organic matter in the water can improve soil aeration, water-holding capacity and cat- ion exchange capacity (CEC). An initial study was performed in 2011, and Oberholster and colleagues followed up in with a 2013-14 study to evaluate the impact of treated winery wastewater irrigation in two commercial vineyards—one in Napa Valley and one and Alexander Valley. They investigated water quality, soil com- position, vine health, grape composition at véraison and harvest, wine chemistry and the sensory characteristics of aroma and taste. Both blocks had identical vineyard and wine- making practices. Grape composition was analyzed at véraison and harvest for chemical composition, tannin, phenolic and cation. At Site A, there were no significant differ- ences in grape chemical composition, grape phenol composition or wine phenol composi- tion, though the latter might partly be due to the character of white winemaking. At the second site, the grapes were picked at different times due to rainfall. Still, there was little significant difference between con- trol and treatment samples in grape chemical composition. Grape anthocyanins were simi- lar, but tannin total phenols were different due to different ripeness levels, not the irriga- tion treatment. Though the tests had limitations, Oberhol- ster and her colleagues concluded that there was very little buildup in the soil. —Paul Franson Does Winery Wastewater Affect Vines, Grapes and Wine? RESEARCH SITES COMPARED Site A: Napa Valley (2013) Site B: Alexander Valley (2014) Control Block Treatment Block Control Block Treatment Block Wine Chemical Composition RS (g/L) 0.48 (±0.04) 0.35 (±0.08) 0.13 (±0.02) 0.37 (±0.02) pH 3.32 (±0.01) 3.38 (±0.00) 3.41 (±0.02) 3.57 (±0.07) TA (g/L) 6.25 (±0.02) 5.66 (±0.01) 6.38 (±0.16) 6.33 (±0.25) %EtOH 14.71 (±0.02) 14.51 (±0.03) 15.11 (±0.13) 15.09 (±0.08) ANITA OBERHOLSTER / UC DAVIS