Nitrogen requirements of Pinot noir based on growth parameters, must composition, and fermentation behavior

Authors: Schreiner, Roger - Paul; OSBORNE, JAMES - Oregon State University; SKINKIS, PATRICIA - Oregon State University

Submitted to: American Journal of Enology and Viticulture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/11/2017
Publication Date: 1/1/2018
Citation: Schreiner, R.P., Osborne, J., Skinkis, P. 2018. Nitrogen requirements of Pinot noir based on growth parameters, must composition, and fermentation behavior. American Journal of Enology and Viticulture. 69:45-58. https://doi.org/10.5344/ajev.2017.17043.

Interpretive Summary: The nitrogen requirements for grafted Pinot noir grapevines were evaluated over a three year period using a pot-in-pot vineyard that allowed for precise control of nitrogen supply. The impact of nitrogen on vine vegetative and reproductive growth parameters, and on fruit composition and fermentation behavior of musts was used to define better nitrogen needs and were equated to leaf and petiole tissue nitrogen status guidelines. Nitrogen had a greater impact on vine shoot and leaf growth than on yield or flowering, indicating that growers can reduce N supply to limit plant size before suffering a yield loss at the current yield targets for premium wine production. Nitrogen in the must needed by yeast to complete fermentation, known as YAN, was also strongly affected by nitrogen supply leading to slower rates of fermentation. However, the level of YAN needed to achieve a reasonably fast fermentation was lower than previous recommendations. Tissue test guidelines for nitrogen in leaf blades and petioles to achieve a good balance of less shoot growth with no yield loss and reasonable fermentation times were defined for Pinot noir.

Technical Abstract: A study to reassess the nitrogen (N) requirements for Pinot noir was carried out using a pot-in-pot vineyard where N inputs were carefully controlled. Pinot noir grafted on 101-14 rootstock was exposed to five levels of N supply delivered via fertigation beginning in their fourth growing season, and vine productivity, berry chemistry and must fermentation dynamics were studied over three years (2012-2014). N supply altered the N status of vines in accordance with expectations leading to distinct levels of N concentrations in leaf blades and petioles with minor variations by year. Varying N supply had greater impact on vegetative growth parameters than upon reproductive responses. For example, leaf area at veraison of vines exposed to the three lowest rates of N supply was reduced in all years, but yield was only reduced in the lowest N rate vines in 2012, and the two lowest N rates in subsequent years. Fruitfulness and fruit set were only slightly reduced by low N supply, while flower number of inflorescences was unaffected by N supply. Effects on berry maturity indices at harvest (soluble solids, pH, and titratable acids) were generally small, but effects on must yeast-assimilable nitrogen (YAN) concentrations were quite large. YAN was reduced from about 200 mg N/L in the Control to as low as 25 mg N/L in the lowest N rate after three years. Treatments with lower YAN required more time to complete alcoholic fermentation, particularly those with YAN below 100 mg N/L. However, all fermentations, even those with YAN as low as 25 mg N/L, fermented to dryness. Reducing vegetative growth of Pinot noir can be achieved prior to reducing yield when vines are cropped at typical levels for premium wine production in the region. YAN levels as low as 100 mg N/L might be a better production target for wineries to achieve minimum fermentation requirements of Pinot noir.