Determining the Impacts of Dormant Pruning Methods and Nitrogen Fertilization on Pinot Noir Bud Fruitfulness and Yield

This project is designed to provide scientifically tested information to growers about the impacts of two commercial management practices that can influence vineyard productivity: dormant pruning and nitrogen (N) fertilization. The Oregon industry uses primarily cane pruning for Pinot Noir, as they believe spur pruning will result in low yields (due to low bud fruitfulness) and reduce wine quality. Objective 1 of this study tests this question in a commercial vineyard, and we have been able to show with year 1 data that spur-pruned vines have fruitful basal buds, and that fruit composition and vine growth are equitable to that of cane-pruned vines. Although cluster size is smaller in spur-pruned vines, it was not enough to cause differences in whole vine yield. Results from our N-fertilization trial show little effect on bud and actual fruitfulness and yield after two seasons. Both experiments highlight the impact of vine vigor on bud fruitfulness, with greater fruitfulness observed with higher cane weights in the nitrogen trial and higher internode diameters in both pruning and fertilization trials. Additional years of this research will help determine the impacts of these management methods on yield potential over different seasons and vineyards to help growers adopt new pruning practices and/or enhance their vineyard N-management.

A Researcher-Industry Partnership to Understand the Yield-Quality Relationship in Cool Climate Pinot noir and Chardonnay Production

The long-term crop load study continued during 2017, the project’s sixth season. Eleven companies conducted the research on-site in 12 vineyards during 2017. Yields were the second highest in the six years of the study, second only to 2015. Average yield across all crop thinning treatments and sites was 1.13 lb/ft, which is higher than the 6-year mean of 0.93 lb/ft. Seasonal heat unit accumulation for 2017 was the lowest since 2012, and harvest was later than in recent years. However, fruit had sufficient ripening with total soluble solids (TSS) ranging from 21.0 – 25.0 °Brix. Analysis of harvest data across all sites in 2017 shows that fruit composition was affected by vineyard site and crop level. Treatment effects were tested within each vineyard site, and results show that only half of the sites (50%) had some treatment effect on fruit composition; however, the effects varied by site. There was no single fruit parameter that was affected by crop level at all sites, and the most common differences found by treatment were for TSS and pH in 2017. However, only 25% of vineyard sites had a difference in TSS with cluster thinning. Multiple regression analysis of data across the first five years (2012-2016) shows that crop load (yield: pruning weight, Y:PW) was related to TSS more than yield alone. Yield, however, was related to anthocyanin, pH and TA, with higher yields predicting lower pH, TA, anthocyanin, and tannin but higher TA. Fruit YAN was best predicted by pruning weights and Y:PW, not yield. Expert evaluation of wines from the 2012-2014 vintages show no yield effect on wine sensory perception, as wines did not group by yield level for descriptive analyses. According to industry collaborators surveyed, 43% had sufficient confidence in the study’s findings that they adopted higher yield targets in their vineyards beyond the research project, citing the ability to increase yield without compromising quality, and in recent warm years higher yields were preferred by winemakers.

Determine The Impact of Cluster Thinning and Cluster Zone Leaf Removal on the Hormone Content of Pinot Noir Grape Berry

During the past six months we have succeeded to reproduce the flower-to-berry monitoring procedure developed in our lab with similar outcomes. The justification of this procedure is to mitigate the extreme variability of flowering events in a cluster that is assumed to explain the berry variability. Using this procedure, we were able to distinguish “early” berries (emerging from early flowering events) from “late” berries (emerging from late flowering events). Previous observations in our group suggested that flowering time was not the major contributing factor of the ripeness variability at mid- véraison stage (50%of berries are green and 50%are colored) . This was confirmed again this year via the monitoring of several phenological parameters on “early” and “late” berries. We also confirmed that the seed weight relative to seed weight better explained the ripeness of individual berries at mid-véraison stage regardless of whether berries were categorized in the early or late berry groups. Interestingly, by monitoring berry size and berry weight, we also found that “early” and “late” berries rapidly overlapped their growing curves during the early stages of the growing season (week 3 to week 6 after bloom), which suggests a developmental mechanism to mitigate developmental variability among berries of a cluster.

On the other hand, ripeness variability at véraison was not associated with berries being “early” or “late” as both berry groups had a wide range of ripeness level at mid-véraison stage (sugar and pigment content). We also validated the effects of two viticulture practices (cluster thinned and fruit-zone leaf removal) on sugar and pigment contents regardless of whether berries were “early” or “late”. In vines with clusters thinned at 0.5/shoot, both accumulation of sugar and pigment contents were significantly higher in berries during the late stages of the ripening. For the fruit-zone leaf removed, only pigment content was significantly increased in sun-exposed clusters during weeks 12-15. The fine screening we performed to mitigate the developmental variability of berries has been successfully conducted and we are in the second phase of the project this year, which is the quantification of hormone and metabolite in control, cluster thinned, and fruit-zone leaf removed grapevines.

Comparison of Crop Load Management Systems and Differential Regulated Deficit Irrigation (RDI) on Vegetative Compensation, Whole-Canopy Photosynthesis, and Vine Performance in Procumbent Vitis vinifera L. in a Warm Climate

A traditionally managed head-trained, cane-pruned Merlot/Freedom vineyard planted on a California sprawl trellis was converted either to a bi-lateral cordon spur pruned (HP) or single high-wire bi-lateral cordon mechanically pruned (SHMP) crop load management system. Two irrigation treatments were applied. Vineyard was irrigated as follows A control treatment of sustained deficit irrigation (SDI) at 0.8 of estimated ETc was applied from anthesis until harvest (EL Stage 38) with a mid-day leaf water potential (¥[1]) threshold of -1.2 MPa. A regulated deficit irrigation (RDI) treatment was applied at 0.8 ETc from anthesis to fruit set (EL Stage 28) with a ¥[1]  threshold of -1.2 MPa, 0.5 ETc from fruit set to veraison (EL stage 35) with a ¥[1]  threshold of -1.4 MPa and at 0.8 ETc from veraison until harvest with a ¥[1]  at -1.2 MPa. Irrigation treatments were not initiated until ¥l reached -1.0MPa for vines in the 0.8 Etc treatments. It took one season to convert and establish canopies that can be cropped. In 2014 the  vineyard was cropped. The SHMP treatment irrigated with the SDI irrigation method generated the largest canopy earlier and was the most efficient user of applied water to fix carbohydrates. Furthermore, this canopy also yielded the greatest with acceptable canopy architecture and microclimate variables for the warm climate. There were few statistically significant effects of crop load management treatments or irrigation methods applied on seed and skin flavonoids. The total berry skin anthocyanins were most affected by the HP and SDI treatments in the initial year of data collection. The preliminary results suggest that it would take one full growing season to convert traditional California sprawl canopies to a SHMP trellis. The resultant canopy is a more efficient user of applied water amounts to fix carbon with greater yields with similar berry skin phenolics. The study is providing important science-based information for California wine[i] grape growers on how best to manage traditional California sprawl canopies to a SHMP trellis. The resultant canopy is a more efficient user of applied water amounts to fix carbon with greater yields with similar berry skin phenolics. The study is providing important science-based information for California wine grape growers on how best to manage traditional vineyards in times declining resources such as labor and water.

Defining Crop Load Metrics for Quality Pinot Noir Production in Oregon

A three year study began in 2013 to determine the impact of varying crop levels on vine growth and balance. The project involves two components: 1) a large grower collaborator crop load study and 2) a study that monitors vine growth, nutrition and physiology measures within four sites from the larger study. A total of 13 vineyard and winery collaborators have participated in the research and completed two full growing seasons of data collection and wine production for the study in 2013 and 2014. The 2013 season results from the large grower collaborative study indicates few differences in vine size (pruning weight), vine nutrient status, or fruit composition at harvest. Data from for the 2014 season are still being gathered from collaborators and will be analyzed statistically in spring/summer 2015. Data obtained from the four detail sites during 2013 and 2014 show no difference in vine nutrition at bloom or véraison, vine photoassimilation rates, nor differences in vine growth and leaf area when comparing full crop (non-thinned vines) with those cluster-thinned to one cluster/shoot. Despite very high yields in 2014, cluster thinning did not drastically change ripeness parameters measured. The differences in vine productivity among sites within the two projects are valuable in understanding how crop load may be influencing fruit composition and quality in vineyards with different yield capacity. The data obtained from the first two years of this research suggests that the Pinot noir vines in the Willamette Valley of Oregon may reach vine balance on their own and do not require cluster thinning to adjust for fruit ripeness or to maintain vine growth. Further seasons of research are required to better understand the role of vine balance.

Defining Crop Load Metrics for Quality Pinot Noir Production in Oregon

A three year study began in 2013 to determine the impact of varying crop levels on vine growth and vine balance. The project involves two components: 1) development of a large grower collaborator crop load study and 2) monitoring of vine growth, nutrition and physiology measures within four sites from the larger study. During 2013, the project included a total of 13 vineyard and winery businesses from across six AVAs in the Willamette Valley of Oregon. Collaborators successfully completed their first season of data collection as of this reporting, and results are being compiled and analyzed in winter 2014. The additional data from the four sites within the study are being analyzed in winter 2014, but preliminary data that shows no difference in vine photosynethetic assimilation or vine nutrition at bloom or véraison when comparing full crop (non-thinned vines) with those thinned to one cluster/shoot.

Improving Yield and Quality of Sauvignon Blanc

Clonal Trial: During the 2010 growing season, a trial containing 12 clones of Sauvignon blanc were grown and harvested. The vineyard is farmed organically, drip irrigated and planted in a Russian River loam soil in Hopland, Mendocino County, California. Clones include: UC FPS# 1, 6, 7, 14, 18, 20, 22, 23, 25, 26, and 27. The experimental design is a ANOVA Randomized Complete Block with 8 replications of 5 vine vines planted in 4 long east ?west rows. Replications are clearly marked with plastic cattle ear tags at the beginning and end of the plot containing the replication number and clone for easy identification. This is the fifth bearing year of the vineyard, and the vines were trained with two canes containing an average of 12 buds per cane on a vertical shoot positioned trellis (VSP). Vines were managed during the growing season to the cooperating grower?s commercial standards including trunk and cordon suckering and removal of sterile shoots, positioning shoots upright inside of fruiting wires, and a standard powdery mildew program utilizing stylet oil and wettable sulfur pre-bloom, and sulfur dust post bloom. No insecticides or miticides were applied. Nearly all vines are bearing at commercial levels, and we were able to sufficiently harvest enough fruit to make valid mean comparisons. This growing season was relatively cool and overcast. Consequently, the growing season was delayed by almost two weeks. Bud break occurred between April 1st and April 7th. Flowering occurred between June 15th to June 18th. Veraison was also late, between August 4th to August 12th. Harvest occurred on October 8th, and was scheduled to coincide with other Sauvignon blanc being crushed by the cooperator. In general, phenology was not significantly different between all of the clones. The exception is that veraison and ripeness were accelerated for UC FPS # 14 which generally has lighter crop loads ( Target fruit maturity was 22.5 to 23.5 %brix.) Based on our data, these observations were concluded: ? The vines are becoming mature and are probably yielding within their commercial potential. Vine yield have a statistically significantly different range, from 3.7 kg to 9.9 kg, which would correspond from 3.2 to 8.5 tons per acre. Cluster counts are also significantly variable, from 31 to 65 clusters per vine. ? There are differences in cluster weights ranging from approximately 81g to 133 g. There is considerable variability in the clones in cluster size, looseness and yield potential. This allows growers some choice if they are in need of lighter crop loads to insure that fruit will ripen under cooler conditions. ? Fruit ripeness varied from around 21 %brix to 24 %brix. It appears that ripeness was affected by crop load. Clones that were carrying heavier crops were less ripe at harvest. ? The pH was higher than is typical for the cultivar in our region (ranging from around 3.5 to 3.7) and titratable acidity was moderate (ranging from .5 to .7 grams per 100 ml). Often fruit from our area has more acidity, but because of the large crop and the long hang time, acidity was lower than harvests that mature early and are lighter in size. ? UC FPS #1 is still an excellent clone, and yields consistently well from one season to the next. Trellis Trial: The trellis trial is in adjacent row to the variety trial. The experimental design is a randomized complete block, with 4 reps of 10 vines for each treatment. The trellis types were selected with the ability to be mechanically harvested. The following trellis types are being used: 1. Vertical Shoot Positioned Trellis (VSP), bilateral cordon, highway post, fruiting wire at 36 inches. 2. VSP, 4 canes, with 2 pairs stacked on fruiting wires at 36 inches and 44 inches. 3. VSP, bilateral cordon, fruiting wire at 36 inches, 12 inch cross arm at 48 inches, and 16 inch cross arm at 60 inches to create more pendant growth to help divigorate the vines (a modified California sprawl system). 4. VSP, modified cane pruning (continuous fruit curtain), cordon wire at 36 inches, 4 short canes are tied to fruit wire at 44 inches. 5. VSP, 4 canes tied to two parallel fruiting wires at 36 inches, two cross arms, one at 48 inches, and one at 66 inches. In 2009, we balance pruned the vines, meaning that we left 3 bud spurs, and tried to have an average of 40 buds per vine. Regardless, it is clear that the cane pruning systems are able to set larger crops than spur pruning systems.

Cultural Practices to Modify Berry Physical Properties and Susceptibility to Cracking

Ethrel sprays, irrigation regimes, and girdling all had a significant influence on Flame Seedless cracking in the 2010 field trials at Arvin, CA. Among the 64 treatment combinations of these factors, ethrel sprays had the largest effects, particularly the first ethrel spray, which increased cracking rate by six-fold compared to plots with no spray. This suggests that the dose and timing of the ethrel spray may be a key issue in balancing the advantages for color development with disadvantages of cracking. The four irrigation treatments, 0.6X, 1X (grower standard), 1.7X and 2.3X, caused clear differences in plant water status as measured by stem water potential (SWP), with berries from the higher irrigation treatments having significantly increased berry size, but also increased cracking, and berries from the lowest irrigation having decreased size, firmness, and cracking. Cell turgor was also well correlated with berry firmness. The correlation between irrigation and cracking justifies the prospect of future usage of SWP and other linked berry properties to monitor and minimize cracking, and we will continue research to resolve these factors in order to provide growers with information about threshold values for cracking. Girdling also significantly increased cracking with the late girdle having higher effects than the early girdle. Late girdle may not be as necessary for this field considering its negative impact on cracking but minor effects on color development.

Tracking of individual berry growth showed that berries at around veraison expanded with an average rate of about 2.5% per day, but most of the expansion occurred at night. A peak short-term rate equivalent to 6.4-8.5% per day was exhibited at 7-8am, but the monitored berries that showed these rates did not crack. Skin mechanical properties in the standard and frequent irrigation treatments were tested with custom equipment (berry balloon system, BBS), and in both treatments, pressure, stress and skin strain at failure (cracking) progressively decreased over berry development, indicating, as expected, that cracking susceptibility increases over time. In the scanning electron microscope (SEM) the surfaces of field-cracked, soaking-cracked, and BBS-cracked berries all showed clear evidence of failure by cell wall breaking and not cell separation, contrary to current scientific thinking. The BBS also detected varietal differences (Flame seedless vs Syrah) in skin mechanical properties, and given the strong impacts of ethrel spray on cracking, it will be important to quantify skin properties with BBS for the different ethrel treatments in 2011. Flame seedless berries were soaked in water with only the stylar end or the longitudinal side immersed, and berries cracked at the stylar end in the former case but remained intact in the latter. Soaking of entire flame seedless berries in water confirmed that berries crack at a fairly low strain (<5%). These results and our SEM images showing broken cell walls, indicate that cracking is most likely a local event that is initiated by failure of a few cells rather than a consequence of an overall expansion of the flesh, as previously believed.

The Determination of Crop Coefficients for Central Coast Vineyards

This project has further developed and applied a novel method for determining the site-specific irrigation crop coefficient, based on measurements of the midday canopy shaded areas using large solar panels. The canopy shaded areas were measured at eight vineyards throughout the growing season in San Luis Obispo County, and converted to crop coefficients. Together with local reference evapotranspiration and irrigation application data, the irrigation applications were expressed as a percentage of the full potential vine water use.

This technique makes it truly practical to fully utilize the equation developed by Williams and Ayers, which correlates the midday canopy shaded area to the irrigation crop coefficient. Prior to the development of this solar-panel method, the use of this equation was largely limited to research purposes, as the effort required for measuring the canopy shaded area using the existing manual or photographic techniques was impractical for commercial operations. The site-specific crop coefficients that a grower can collect with this method will allow one to apply climate-based irrigation scheduling with more confidence, less risk, and more consistency season after season. The large differences between the crop coefficients measured at sites that had similar trellis systems indicate that there is a value in measuring these coefficients locally.

With accurate crop coefficients it becomes possible to perform detailed evaluations of irrigation management at a given site, quantifying the season?s irrigation applications as percentages of the full potential vine water use. These results show, likely for the first time, just what degree of irrigation deficit the test plot vines were subjected to during the growing season.

Inception, Diagnosis, and Consequences of the Berry Shrivel Disorder

Berry shrivel (BS) is a disorder of unknown cause and sporadic appearance that has been increasingly observed in vineyards in Napa and Sonoma Counties. BS is commonly misdiagnosed as bunch stem necrosis (BSN), but we have found that the disorders can be clearly distinguished based on the presence of a healthy, green rachis in BS compared to a necrotic rachis in BSN-affected clusters, and the fact that BSN berries have normal to high Brix whereas BS berries have much lower Brix than normal berries. This was the second year of our study of BS development, and the first in which BS was prevalent enough to obtain a representative sample of BS berries over time. In order to determine whether BS is a berry, cluster, or vine level phenomenon, a substantial amount of over-sampling was required, and hence not all the 2005 samples of berry composition have been analyzed to date.

In both 2004 and 2005, around the time of veraison, and prior to any appearance of BS symptoms, BS berries were firmer than control berries, but the decline in firmness at veraison was faster in BS than in control berries, so that for most of the post-veraison period, BS berries were softer than controls. In 2004, BS fruit skin had a slightly increased mass of cell wall material compared to the skin of control berries, and a slightly reduced amount of cell wall material in the mesocarp, indicating that the disorder may be related to metabolic aberrations in cell wall metabolism in the mesocarp. In 2005, with a larger sample size, this was not the case. It is also unclear to what extent BS is associated with water stress. In Oakville, vines which historically have exhibited BS have been consistently less stressed than controls, but the opposite trend was observed in Sonoma County, and in nether location was the degree of BS associated with the level of water stress, as measured by leaf water potential.

In both 2004 and 2005, visual symptoms of shriveling, whether caused by BS, cluster girdling, or cluster excision, were always associated with a loss in mesocarp cell viability (as indicated by a fluorescent vital stain), and hence we can attribute the shriveling to cell death, rather than simply to berry desiccation. In both years there has been no apparent difference between BS and control berries in the xylem connection between the berry and the pedicle. For the 2005 berry composition data that is available, BS berries were similar to berries on girdled clusters, in that they both accumulated less soluble solids and had a lower pH than control berries. One key result from 2005 is that there is also evidence that BS symptoms, as measured by essentially all of the major indicators of berry development (Brix, pH, dry weight), are progressive over the season and are also expressed at the whole-vine level. Berries that show early symptoms of BS are the most affected, but lesser degrees of symptoms also occur in berries that are affected late, and still lesser, but measurable, symptoms occur on apparently healthy berries from affected vines. These results strongly suggest that, for a vineyard that is affected by the BS disorder, the effects of the disorder may not be limited only to clusters exhibiting shriveled berries.

Our current hypothesis is that BS is not a disorder related to xylem function and vine water relations, as thought previously, but rather a disorder either of phloem function and/or of vine photosynthesis. Wines were made from commercial Cabernet fruit (BV vineyard in Rutherford) that was either free from BS, or had varying levels of BS (5, 10, or 15%by weight), or BSN (40%by weight) fruit. In all cases, fermentation proceeded normally, and these wines will be subject to sensory and chemical analysis.