The overall goal of this project is to understand how nitrogen fertilization in the vineyard as compared to nitrogen supplementation in the winery affects wine properties in both a red and white cultivar. To achieve this goal, we are working in 2 vineyard blocks (Pinot noir and Chardonnay) each with a history of low nitrogen status, so that nitrogen can be added in the vineyard (to boost native must YAN) and also in the winery (to boost either ammonium-N or organic-N components of native YAN). Each variety trial has 4 treatments being evaluated using 4 replicates from the vineyard. The treatments are:
- A) No N in vineyard + No N added in winery
- B) No N in vineyard + DAP in winery
- C) No N in vineyard + ORG-N in winery
- D) N Fertilized in vineyard.
The Pinot noir block was used for this trial beginning in 2015, but 2016 was the first year for Chardonnay. Unfortunately, the Pinot noir block was mistakenly tilled (alternate alleyways) by the vineyard crew in early April of 2016. We therefore, quickly replanted a grass cover crop in those alleyways, but the establishment was rather poor. The N fertilized treatment for both vineyards received 3 additions of 20 pounds per acre N, for a total of 60 pounds in 2016. We will likely reduce this to 40 pounds total in 2017, depending on results. The vineyard N addition in 2016 increased vine N status in both blocks, but the Chardonnay block responded faster and had a larger change than the Pinot noir block. The resulting must YAN levels were increased in N-fertilized vines by 38%in Pinot noir (from 176 to 243 NOPA YAN) and by 90%in Chardonnay (from 99 to 189 NOPA YAN). The vineyard N addition did not influence growth or yield of Pinot noir, nor growth of Chardonnay. The unfertilized treatment that was slated to receive organic N supplementation in the winery (treatment C) did have lower yield than the N-fertilized treatment in Chardonnay, but the other 2 treatments did not differ from the N-fertilized. Fruit solar exposure and vine water status were not altered by N fertilization in either variety in 2016. After winery additions to treatment B (+DAP) and C (+ORG-N), the N-fertilized and winery supplemented N treatments (B, C and D) had higher YAN than the Control (A) in Pinot noir. In Chardonnay, the + DAP (B) and N-fertilized (D) had the highest YAN, the + ORG-N (C) was lower than those 2 treatments, and the Control was lower still in YAN. The Pinot noir musts from N-fertilized vines fermented 1 day faster (significant at P < 0.05) than all other musts, even though YAN was just as high in the +DAP and +ORG-N musts. In Chardonnay, the Control musts with lowest YAN took about 2.5 more days to complete ferment than all other treatments, but this was not significant (P > 0.05). The sensory analysis of the 2016 wines will begin this summer.