Dr. Paul Schreiner, research plant physiologist, USDA-ARS and Oregon Wine Research Institute, has prepared the update below. This project receives funding from the Oregon Wine Board as part of its viticulture and enology research grant program.
Objectives
Paul Schreiner, USDA, and a team of researchers (Tian Tian, Patty Skinkis, James Osborne, Elizabeth Tomasino and Michael Qian from Oregon State University, and Jungmin Lee from USDA) are examining the viticultural impact of nitrogen (N) use in the vineyard on Chardonnay and Pinot noir and the resulting impact on wines as compared to winery N additions. This research will determine which of the following produces better wines:
- Use of N fertilization in the vineyard to boost native must N levels in the fruit
- Maintaining low N status in the vineyard combined with winery N additions
- Maintaining low N status in the vineyard without winery N additions
This research will provide new guidelines for Oregon producers to improve quality and profitability by managing N inputs in both the vineyard and winery, and potentially reduce the environmental footprint of wine production.
Process
To achieve these goals, replicated trials in two vineyards (Pinot noir and Chardonnay) with a history of low vine N status are being conducted over multiple years. Fruit N levels are being manipulated in the vineyard by fertilizing some vines, or in the winery by supplementing musts from non-fertilized vines using either an organic or inorganic N source. The control treatment is from non-fertilized vines with no winery N addition.
The influence of N fertilization on numerous vine growth and physiological measures are being quantified. The resulting impact on wine composition will be assessed using a sensory approach. More detailed biochemical analysis of wines will be pursued as warranted by sensory findings.
Findings and Next Steps
Results from 2016 showed that N fertilization increased vine N status (based on leaf blade N) and must N levels in both varieties, but the increases in Chardonnay were larger than in Pinot noir. Vineyard N addition did not increase vine growth or yield in 2016. The Pinot noir musts from N-fertilized vines fermented one day faster than all other musts, even though must N levels were similar in the two winery N addition treatments. In Chardonnay, the control musts with the lowest N took about 2.5 more days to complete fermentation than all other treatments.
Preliminary sensory evaluation of the wines by the research team and industry collaborators indicates clear differences in the aroma and taste of Chardonnay wines, and more subtle effects on Pinot noir wines. Rigorous evaluation of the wines by a trained sensory panel will begin in summer 2017 to better define significant sensorial differences between wines.
We will continue to monitor the impacts of vineyard and winery N additions in both varieties over the next two years. A foliar N treatment will be added to the experiment in 2017 and we will investigate how N fertilization also influences fine root growth, colonization by beneficial mycorrhizal fungi, and the status of other nutrients in vines and fruit.
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