Abstract
A three-year study was conducted to investigate the accumulation of yeast assimilable nitrogen (YAN) during the final weeks of ripening in seven wine grape cultivars grown in New York State, and to assess the feasibility of predicting harvest YAN using linear regression models. Berry samples of Vitis vinifera cvs. Cabernet franc, Chardonnay, Merlot, Pinot noir, and Riesling, and interspecific hybrid cvs. Noiret and Traminette, were collected weekly from 49 vineyard sites across the Finger Lakes, Hudson Valley, Lake Erie, and Long Island growing regions from August through harvest. YAN concentrations in Cabernet franc, Riesling, and Traminette were generally low, averaging below 100 mg/L annually, while Chardonnay and Pinot noir showed average YAN concentrations greater than 200 mg/L. During the ripening period, linear regression models were found to predict harvest YAN up to five weeks prior (R2=81.6%). A decrease in YAN during ripening was observed across cultivars, caused primarily by decreases in ammonia (AMM), as PAN levels remained stable. Population distributions were used to estimate appropriate prophylactic nitrogen additions for each cultivar, minimizing the risk of deficiency or excess; this was most difficult with Chardonnay, Noiret, and Pinot noir, which had the highest and most variable YAN concentrations, and subsequently run the greatest risk of over-supplementation with prophylactic additions.
- ©2014 by the American Society for Enology and Viticulture
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