Comparing Nitrogen Fertilization in the Vineyard versus Supplementation in the Winery on Quality of Pinot noir and Chardonnay Wines and Productivity in the Vineyard

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.

Establishing Critical Values of N and K for Grapevines

Petioles were collected in three different vineyards at bloom, veraison and just prior to harvest. The Thompson Seedless vineyard was located at the Kearney Ag Center; the Chardonnay vineyard was located in the Carneros district of Napa Valley and the Cabernet Sauvignon vineyard near Oakville in the Napa Valley. Prior to bloom the following treatments were imposed: 1.) Vines that were not irrigated prior to bloom, 2.) Vines that were irrigated several times prior to bloom and 3.) Vines that were fertilized and then irrigated. Two fertilizer amounts were used in the Thompson Seedless (50 and 100 lbs. N per acre) and Cabernet (40 and 80 lbs. N per acre) vineyards while only one fertilizer amount was used in the Chardonnay vineyard (80 lbs. N per acre). The Non-irrigated treatment in the Thompson Seedless and Cabernet vineyards at veraison and pre-harvest consisted of vines in which irrigations were terminated two weeks prior to sampling. The Non-irrigated treatment in the Chardonnay vineyard was not irrigated all season long. Each treatment was replicated four times at the three locations.

At the bloom and veraison sample dates, petioles were collected at various times during the day; 0800, 1200 and 1600 hours. At veraison and prior to harvest petioles were also sampled before sunrise. On all three dates, petioles were taken from leaves exposed to direct sunlight and leaves that were in the shade at the time of sample. At bloom, petioles were also sampled from leaves opposite the cluster.

At the time this report was written not all of the petiole samples had been ground for nutrient analysis. In addition, none of the leaf, stem or clusters sampled from each treatment on each sample date had been ground. However, it was possible to analyze all petiole samples from one block at bloom, veraison and pre-harvest in the Thompson Seedless vineyard and all samples in one block at bloom and veraison in the Chardonnay and Cabernet vineyards.

Based upon the limited data reported on herein, several conclusions could be reached. As expected, N fertilizer application had a significant effect on petiole nitrate-N and total N at all three locations on all three, sample dates. The potassium nitrate fertilizer also significantly increased petiole K. Sampling leaves exposed to direct sunlight versus those taken from the shade had a significant effect on petiole nitrate-N and K. At bloom, petiole nitrate-N was generally greater in the sunlit leaves compared to the shaded leaves. The petioles of sunlit leaves collected at veraison and pre-harvest, however, had lower nitrate-N and K values than the shaded leaves in all three vineyards. In addition, petioles collected from leaves opposite a cluster had lower values of nitrate-N and K at the three locations. Irrigation amount (no applied water vs. applied water) also affected petiole nutrient status. In general, non-irrigated vines had greater values of nitrate-N than the irrigated vines. The results indicate that leaf type and irrigation amount will affect petiole nutrient values. Whether time of day significantly affects petiole nutrient status awaits the analysis of additional replications at each location.

PDF: Establishing Critical Values of N and K for Grapevines

The Effect of Application and Timing of Cryolite on Fluoride Levels in Red and White Wines

The purpose of this experiment was to determine the level of fluoride in red and white wines from grapes sprayed with Cryolite at specific rates and application times. A five-year study conducted by CSU Fresno has conclusively shown that applications of Cryolite increase fluoride levels in red and white wines. From 1990 to 1994, different rates and timing combinations were tried in an effort to clarify the role of Cryolite in wine fluoride. In 1994, confirmation of a 6-pound full bloom rate was the basis for an application and timing trial tested on seven different vineyards in the northern, central, and southern San Joaquin Valley. Zinfandel, Barbera, Chardonnay, French Colombard, Muscat Canelli, and Thompson Seedless varieties were studied (Table 1). At CSU Fresno, a replicated experiment was performed on Thompson Seedless, Zinfandel, and French Colombard. The treatment schedule is listed in Table 2. Treatments were applied at each site using grower-supplied equipment. At Simpson Vineyards, because of a change in cultural practices, vines were sprayed with a backpack sprayer. At CSU Fresno, applications were made with a single row over-the-vine boom sprayer. Application dates for each site are shown in Table 3. Insect populations were monitored frequently during the growing season. No plots received applications of other non-fluoride containing products, but all other normal cultural practices were performed. Soil and water samples were taken from each site at the start of the experiment, and water samples were taken just prior to each application, to analyze for fluoride. Samples were analyzed by the Ion Selective Electrode (ISE) method. At harvest, grapes from each treatment were crushed, some juice kept aside, and the remainder made into wine. Grape juice was analyzed for fluoride by ISE., The wines were bottled and analyzed for fluoride by ISE. The water and soil fluoride levels are listed in Table 4. Water fluoride levels ranged from 0.04 to 0.48 ppm. Soil levels ranged from 0.59 to 1.73 ppm. Soil and water do not greatly influence the fluoride levels found in wines made from grapes sprayed with Cryolite, because the levels of fluoride in wines were not consistently higher to correspond with these water and soil levels. Both untreated control (Tl) juice and wine samples had less than 1 ppm fluoride. Wine and juice samples that received 6 pounds at bloom or pre-bloom (T3 or T4) had between 0.27 and 1.94 ppm fluoride. Applications at shatter (T5) had the highest fluoride levels, leading to the conclusion that later applications cause increased fluoride levels. Results of juice fluoride samples are listed in Table 5 and wine fluoride samples are listed in Table 6.

Vineyard Management Strategies for Potassium Nutrition and Optimum Winegrape Quality

There has been some clear progress on the potassium (K) fertility issue in symptomatic North Coast vineyards. These vineyards are typically on soils with K fixing clays (some also with high Mg), and often have “not responded” to earlier conventional applications of potassium sulfate. We have used high rates of potassium sulfate (81bs or greater of potassium sulfate per vine) and supplemental irrigation (2 to 4 times the standard rate) to decrease K fixation and increase the availability of K for root uptake. This has successfully increased vine K status and maintained high K status beyond veraison. The genetic approach to managing these soils also looks promising. For Chardonnay vines on low K soil, vine K status was significantly greater on 5C and St. George rootstocks than on four other root systems. Applications of K to these vines increased juice pH on some rootstocks and decreased the concentration of malate on all rootstocks.

Improving nitrogen fertilizer efficiency in winegrapes

This was a four-year study on the effects of N fertilizer timing and rate on vine N status, fruit composition and quality, and vine yield in four wine cultivars important to the San Joaquin Valley — Barbera, Grenache, French Colombard, and Chenin blanc. It was initiated as a follow-up to previous studies in raisin and table grape vineyards which demonstrated the influence of N fertilizer timing on N availability and utilization and possible improvements in N fertilizer efficiency. Similar studies are needed in wine grape vineyards to determine N timing response as well as effects on vine tissue N levels, fruit composition, and vine yields. N fertilizer treatments included budbreak (BB), berryset (BS), veraison (V), and postharvest (PH) timings at 50 lb. N /ac, BS at 100 lb. N/ac, and check, no N (CKO). N status, as determined by bloom and veraison petiole N03-N and NH4-N (inorganic N compounds) levels, varied among the cultivars and was influenced by rate (0, 50, and 100 lbs. N) and the proximity of fertilizer application prior to petiole sampling date. Grenache and Barbera were the high and low extremes, respectively, in vine N status and responsiveness to N fertilizer application; Chenin blanc and French Colombard were intermediate. Generally, CKO and BS100 were the high and low vine N status treatments through the experiment. PH50 resulted in bloom N levels equal to BB100 and sometimes higher than BB50, suggesting that postharvest timing was the most efficient in supplying N between budbreak and bloom. Otherwise, timing effects on vine N status were minor. Petiole N03-N was more sensitive than NH4-N to N fertilizer treatment differences. However, the sum of the two analyses (expressed as “total inorganic N”) provided the most clear separation among treatment differences and thus could be considered as a useful tool in grapevine N fertility research. Grape soluble solids was the most responsive fruit parameter to N treatment. Generally, N fertilizer tended to decrease soluble solids, irrespective of timing, and with the highest N rate of 100 lbs. resulting in the largest decrease. Titratable acidity differences were mostly inverse to soluble solids. Grenache was the only cultivar with significant yield differences due to N fertilization, suggesting a N-deficient status with this cultivar. All of the N treatments in Grenache, with the exception of V50, increased vine yield over CKO. This result, as well as other negative effects of the V50 treatment, ie.lower titratable acidity and higher pH in Grenache and more cluster rot in French Colombard and Chenin blanc, indicate that veraison may be the least desirable of the timings studied here. The detrimental effects of the high 100 lb.N treatment were also demonstrated, primarily through delayed fruit maturation and some increased cluster rot incidence. The bloom petiole N03-N levels reported here should provide supportive data toward establishing critical vine tissue levels in the wine cultivars studied here.