FY19 AARS Research Year End Report

AARS Viticulture Research Activities FY 19 Year End Report Submitted by Andrew Kirk, Research Specialist, Ashtabula Agricultural Research Station Summary In FY19, AARS personnel conducted research activities in pursuit of OGIC contract deliverables. Research activities focused on a study of grape ripening patterns. Data was collected at AARS and off site to enable a thorough study of grape ripening patterns in the 2018 season. Introduction AARS staff were commissioned in FY 18 to begin a survey of fruit maturity to provide some insight to growers in navigating harvest decisions. There are innumerable factors and decisions made within a vineyard growing season that contribute to the final maturity level of harvested grapes. While this modest research project by no means resolved such a fundamental issue, AARS work in FY 19 did reveal some insight into the dynamics of hangtime, potential for variation within vineyard blocks, and locational differences among sites. As such, this study will provide lines of inquiry for future works of more robust scope. The report is divided into sections covering analysis of the 2018 vintage, variation observed within a Pinot Gris block at AARS, and a locational survey of grape maturity. 2018 Vintage Report in Pinot Gris and Cabernet Franc Background 1600 2018 was a difficult harvest season, 1400 which presented challenges and 1200 opportunities for this research study. 1000 GDD (Figure 1) followed a typical 800 upward trajectory until roughly the GDD (F) second week of October, at which 600 time GDD accumulation slowed 400 considerably, almost to a halt. Early 200 September was characterized by 0 8.5 8.9 9.6 9.1 9.3 8.01 8.13 8.17 8.21 8.25 8.29 9.02 9.14 9.18 9.22 9.26 10.4 10.8 10.2 heavy precipitation (Figure 2), which 10.12 10.16 10.24 was followed by a relatively dry, 2016 2017 2018 Historical stable, pattern through the rest of Figure 1. GDD Progression in 2018 September into October. The result of this was an excellent mid-vintage period, surrounded on either side by difficult conditions for early and late varieties. AARS staff took extensive samples of Pinot Gris, which was harvested during the ideal conditions of late September, and of Cabernet Franc, which was harvested amidst several weeks of cool conditions in late October. All samples referenced were 100 berry samples. In the case of Cabernet Franc samples, these were crushed and then samples were left to “cold soak” for 12 hours overnight. After pressing the next morning, these samples were then frozen for subsequent analysis. Pinot Gris samples were crushed immediately after collection, then pressed and frozen as described above. Pinot Gris 2018 Vintage 16 Pinot Gris samples were taken 14 at harvest from 68 vines at the 12 date of harvest. This same 10 procedure was conducted by 8 AARS staff in 2017, which has Inches 6 allowed for useful comparison Precipitation of the two vintages. 4 2 Substantial differences were 0 observed in the maturity of fruit 8.6 9.5 9.1 9.2 9.3 8.01 8.11 8.16 8.21 8.26 8.31 9.15 9.25 10.5 10.1 10.2 10.3 11.4 from these vines, relative to 10.15 10.25 their 2017 performance. As an Date aside, GDD accumulation was 2016 2017 2018 Historical Average 305 units higher in 2018, despite harvest occurring within one Figure 2. Precipitation during 2018 Harvest calendar day of the previous year’s harvest. GDD accumulation at harvest during the two seasons registered significant interactive effect with total phenolics and titratable acidity but did not have a significant interaction with final Brix at harvest (One-Way ANOVA, p<0.05). This is an interesting result and serves as an affirmation that brix at harvest involves a matrix of factors, not just GDD during the harvest season. Brix Total Phenolics Titratable Acidity 2018 Average from 68 19.4 Brix 568.5 mg/L 5.92 g/L Vines Description of ←→ No Statistically Change, Relative to ↑ Up 13 Percent* ↓ Down 35 Percent* Significant Change* 2017 *95 % Statistical Confidence Interval Between -0.8 to 4.7 % Between 5.3 to 20.2 % Between -39.0 to -33.1 % for percent change Table 1. 2018 Pinot Gris Harvest Maturity, Relative to 2017 Cabernet Franc 2018 Vintage AARS staff selected one vine from each panel of two rows in its Cabernet Franc to monitor in three successive samples throughout the ripening period. The results from this were enlightening as to the limitations of hangtime, in respect to fruit maturity progression. Samples were first taken on 10/12, after a warm first week of October, in which 47 GDD were accumulated. Additional samples were taken then on a weekly basis for two weeks, during which intervals a total of 7 and 4 GDD were accumulated, respectively. In effect, GDD stopped accumulating after the first sample taken. Interestingly, despite relatively low growth in GDD between the first and second sample, brix and total phenolics took a significant step forward during this interval (Table 2). Curiously, Titratable Acidity also rose slightly, despite an expectation that it would decrease with GDD accumulation. These observations have led to a new line of inquiry for future work, which may help growers decide whether to risk additional hang time late in the growing season. The hypothesis would center around a possible lag in the development of sugars and phenolics, relative to when favorable photosynthetic conditions occurred. If berries continue to benefit from photosynthate accumulation that occurred a week or more previously, a grower may have additional motivation, in some instances, to let fruit hang until that benefit has been exhausted. Work in FY 20 will investigate this further. In either case, Cabernet Franc did not benefit in its third week of hangtime, which resulted in no significant change in fruit chemistry (Table 2). Change in Change in Change in Brix Total Titratable from Previous Phenolics from Acidity from Change in Sample Sample Previous Previous Sample GDD from Date Sample Previous week (95 % Confidence Interval) (95 % Confidence (95 % Confidence Interval) Interval) 10/12 - - - 47 ↑ 0.45 to 0.95 ↑ 40.3 to 114.0 ↑ 0.58 to 1.17 10/19 7 brix mg/L g/L ↔ -0.15 to 0.5 ↔ -72.8 to ↔ -0.34 to 0.14 10/25 4 brix 17.0 mg/L brix Table 2. 2018 Cabernet Franc Hangtime Monitoring Performance Variation within a Pinot Gris block A secondary directive within 2018’s fruit 2017 Brix 2018 Brix maturity survey was to examine whether consistent trends hold up within a vineyard block from year to year. To answer this question will require a multi-year effort and an adjusted approach going forward in FY 20. Analysis of samples from the AARS Pinot Gris block in 2017 and 2018 make possible some preliminary observations. Of the key parameters (Brix, pH, TA, Total Phenolics) assessed in the lab by AARS staff, only Brix was subject to an interactive effect between the two years of data. Brix from 2017 was a modest, but statistically significant, predictor of harvest Brix in 2018 on a per vine basis (R2=0.07, p<0.05). Stated in a more intuitive manner, a vine producing poor Brix levels in 2017 would be Figure 3. Geospatial Distribution of Brix. Blue (Low predicted, albeit with moderate confidence, Brix) to Red (High Brix). to do so again in 2018. A vine’s final levels of acidity and Total Phenolics in 2017 were not predictive of its performance in 2018 on these parameters. The persistence of localized areas of weak sugar production is reflected visually in the geospatial distribution of Brix values in the Pinot Gris Block (Figure 3). However, it must be emphasized that variance in 2017 Brix values explained only 7 percent of total variance in 2018 Brix. In other words, 93 percent of the variance observed in Brix must be attributed to factors other than per vine performance variation. 2018 Locational Survey of Fruit Ripening As part of the Ashtabula Terroir project, AARS staff collected samples from various local vineyards throughout the growing season. Although these efforts were executed by means of OARDC SEEDS funding, the work complemented the projects described above and are relevant to this report. Five Pinot Noir vineyards, including that of AARS, were sampled on a weekly basis and subjected to the same procedures described above for Cabernet Franc. Of these 5 vineyards, 4 would be inside the boundaries of the Lake Erie AVA, with the 5th being 13 miles south of its southern boundary GDD on line. 8/29/18 Pinot Pinot Noir Vineyard Description (Nearest Noir Total The notable outlier of Number of Location OARDC Brix on Phenolics these vineyards is that Weather 8/29/18 on 8/29/18 Station) located in Erie County, Ashtabula 1 2,407 16.0 406 35 miles west of ARS Cleveland. By the time Grand River 2 2,407 14.6 301 of Pinot Noir harvest in Valley 1 Grand River Erie County, the closest 3 2,407 16.8 481 weather station to this Valley 2 Geauga site had close to 300 4 2,407 16.6 443 County GDD more than the weather station at 5 Erie County 2,703 19.8 669 AARS. This is the Table 3. Pinot Noir Maturity and GDD at Regional Sites equivalent of roughly 15 summer days difference in heat accumulation. This was reflected in the progression of fruit maturity in Pinot Noir, which was 3-4 brix ahead in Erie County compared to sites in Ashtabula and Geauga County (Table 3).

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