Dr. Patty Skinkis, Professor and Viticulture Extension Specialist, OSU — For more than a decade, my lab has been working to better understand yield management in Oregon with focus on Pinot noir. When I arrived in 2007, there were ~16,000 acres, high demand for Pinot noir and a lot of new plantings. The variety is known to have low yields due to small cluster size. However, yields were kept low by cluster thinning in hopes of hastening berry ripeness, culling underripe clusters, and concentrating berry flavors. At the time, growers were thinning crop to yields around 2 to 2.75 tons per acre (Uzes and Skinkis, 2016). Generally, vines were healthy and vigorous, often bordering on the side of too vigorous, requiring a lot of canopy management. This did not match the vine balance concept–to achieve balance between the vine canopy (its carbohydrate engine) and the amount of fruit (load demand).
The first research projects. I started working on my first research projects to test the timing and intensity of cluster thinning in two research projects, one in the north Willamette Valley’s Dundee Hills (2010-2013) and the other in southern Oregon’s Illinois Valley (2011-2013), both with Pinot noir. We evaluated three thinning levels (0.5, 1, and 2 clusters per shoot) and four time points (bloom, fruit set, lag, and veraison) in a 3 x 4 factorial design with comparison to two full crop treatments (with and without wings removed). That study revealed a few clear results. First, thinning clusters to 0.5 cluster per shoot (1-0-1-0 thinning pattern defined as 1 clusters per every two shoots) was not practical. Most vineyard owners did not see the benefit economically. Also, thinning that low led to increased vine vegetative vigor, more lateral shoots and second crop, particularly if it was conducted early in the season (Skinkis and Reeve 2013). Second, the early and more severe thinning led to increased vegetative aromas in wines. There were generally few to no differences in fruit composition based on timing of thinning. Therefore, we determined that thinning at lag phase was appropriate as the industry standard. Earlier crop thinning was not warranted in healthy, mature vineyards, as the vines were not over- cropped, and cluster thinning was not necessary to balance resources. These studies were conducted in commercial vineyards for three diverse years, including a cool, high-crop year (2011), a low-crop year (2012), and normal season with a wet harvest (2013). All seasons produced variable yields and fruit composition that proved informative but was far from generating a data set from which to make broader recommendations.
A larger effort. Realizing that a more robust effort was warranted to tackle yield management questions in Oregon, we simultaneously envisioning a long-term, grower collaboration project. After two years of planning with industry partners, our team launched the Statewide Crop Load Project in 2012 to evaluate crop thinning amongst as many vineyards as possible over a ten-year period. We focused on thinning levels selected by grower collaborators who applied them at lag phase in a randomized complete block design with at least three field replicates. Growers engaged by implementing the thinning treatments, collecting data, partnering with their winemakers to make commercial scale wines, and conducting sensory evaluations. Our team included 25 companies across seven AVAs and five counties from 2012-2021. The main findings were similar to our first research project: each year and vineyard produced variable results. Cluster thinning did not consistently influence berry ripeness, berry composition, or vine growth or nutrition over the course of the study. This was a bit surprising, as one would assume that the widespread adoption of cluster thinning, particularly to low target yields would surely provide benefit that was quantifiable. The decade that this work was conducted included high, average, and low yield years as well as variability in season heat units and precipitation. The entire 10-year data set is currently being analyzed across all vineyards and years with the help of Dr. Katie McLaughlin, OSU Assistant Professor of statistics. In 2022, the research team collected missing data from collaborators and conducted data quality control, organization, and analyses. We are currently working to develop results summaries in the form of research publications and outreach materials during 2023 and 2024.
The future of yield management. Since the project outset, the goal has been to develop a large data set from areas across Oregon to develop yield management guidelines. The guidelines will not look like specific yield targets for all growers. Rather, we are working to guide decision-making through models developed from the data. To do this work, I am partnering with Dr. A. John Woodill, OSU Research Associate in the College of Earth, Ocean, and Atmospheric Sciences. He is an econometrics researcher with expertise working with complex climate, production, and economics data. He brings the necessary skills to merge these three components into model development. In 2022, I welcomed Louis Delelee, faculty research assistant, into my lab to work on these models. We made great progress in 2022 and are currently working on three models using the Statewide Crop Load Project data set, including a nutrient-yield model, a phenology projection model, and a crop load model. Results from this work will be shared through scientific publications and integrated into industry decision- support web-tools, which we hope to wrap up by the end of 2024.
Testing the winds of change. In February 2023, I contacted approximately 300 companies in Oregon to take part in a yield management study to determine how practices have changed and the impacts on vineyard and winery production economics. The study includes those who produce grapes (grape growers and vineyard management companies). Questions pertained to changes in yield targets, crop thinning practices, farm production costs, and fruit prices. If you received an invitation to complete the survey, please be sure to complete it soon. If you would like to take part but did not receive an invitation, contact me. We will follow up with a winemaker survey later in 2023. These data will be used to inform the larger data set and to share overall findings with members of the Oregon wine grape industry.
As we wrap up these yield management research projects, we are working to make sure information is open and available in formats that are useful to grower and winemaker decision-making. We are in the process of developing a website through OSU Extension where the results will be shared for all years and vineyards in the Statewide Crop Load Project. As noted previously, we are working on decision-support tools to help project harvest yields. This work takes time and resources, so stay tuned for further information and developments as they are available.