The Statewide Crop Load Project is a long term industry-collaborative study that scientifically evaluates the impact of yield on wine quality across Oregon vineyards. The project focuses on Pinot noir, as a recent study in Oregon indicated that it is more commonly crop thinned to specific yield goals in an attempt to reach a higher fruit quality level compared to other varieties in the state. That study revealed how narrow those yield targets are and how universal their application across the state. Considering diverse vineyards and variability of growing seasons, the Oregon Wine Research Institute (OWRI) team began investigating the yield-quality relationship to develop yield management guidelines for Pinot noir producers across different production scales. The best way to develop recommendations for the industry is through long-term research that involves many collaborators across seasons. This is important when considering how different yield management decisions were in 2011 compared to 2015. Having better recommendations can help with production economics and quality when dealing with vintage variation.

The research team is being led by Dr. Patty Skinkis, OSU viticulture extension specialist, who is responsible for the overall project design and analysis of vine growth, fruit composition and collaborator observation data. Dr. James Osborne, OSU extension enologist, is responsible for coordinating wine production protocols, data collection metrics and interpretation of project results. Dr. Elizabeth Tomasino, OSU assistant professor of enology, leads sensory evaluations of wines through winemaker panels and assisted in the development of in-house wine evaluation protocols. Dr. Paul Schreiner, USDA-ARS research plant physiologist, cooperated with Dr. Skinkis in data collection across a subset of vineyards to determine the physiological impacts of yield management on vine water stress, nutrient status and leaf gas exchange (photosynthetic assimilation); he continues to serve as a collaborator on the project for interpretation of vine physiology related data. Finally, Dr. Katherine McLaughlin, assistant professor of statistics, joined the research team in December 2016 to begin working on complex statistics. The team has collected five growing seasons of vine growth and fruit composition data, and three vintages of wine sensory evaluations. With more than 20 commercial vineyards involved in the project over the years, there is a large amount of data being aggregated and statistically analyzed across seasons. However, research results based on statistical analyses of each vineyard and year revealed interesting findings:

  • Cluster thinning has not changed vine health parameters measured, indicating that vines are not over-cropped. This was determined by detailed assessment of the following parameters by Dr. Skinkis and Dr. Schreiner including fruitfulness, vine nutrient status, dormant pruning weights, yield/pruning weight ratios, and carbohydrate and nutrient analyses of dormant cane tissues.
  • Cluster thinning has resulted in some differences in fruit composition. However, the differences have been variable by year and site and are lower in magnitude than most may have hypothesized. The most consistent effect, which was not found in all sites or years, was increases in anthocyanin (red pigments) with lower yields.
  • Impacts of yield on aromas, flavors and overall wine quality assessed for the 2012 and 2013 vintages show little difference based on yield. However, further analysis of data from those vintages is underway.

Dr. Skinkis has given numerous presentations about the study and authored a recent OWRI Technical Newsletter article about the results. The conclusion most growers come to is, “so I don’t have to crop thin?” but the answer is, “not so fast.” The process of research takes time and involves looking at data in complex ways; there is always more to the story. The research team still has to aggregate the data and begin to analyze the results from the “big picture” across all vineyards and years. The basic design of the study must remain unchanged during the duration of the study; however, the research team has evolved how they look at the data over time. Heat unit monitoring began in 2015 to determine how site growth advancement and harvest date may be impacting results. In 2016, the research team began to develop ways to capture industry collaborator observations. This will be conducted through surveys, interviews and in-house wine evaluation that will be conducted by each collaborator starting in 2017. These efforts will enhance the understanding of quality impacts on wine and how processing decisions are being made based on wine resulting from the yield management trials.

To learn more about this research and taste some wines from the project, be sure to attend The Low Down on High Yields: Challenging Yield-Quality Standards for Oregon Pinot Noir session at the Oregon Wine Symposium on February 22. Click here to learn more and register.

Funding for this project has come from varied sources to make the project possible, including the Oregon Wine Board, Oregon Wine Research Institute Pilot Project Fund, and OSU Extension funds generated by the lead PI. The significant donation of time and effort by the industry collaborators has contributed greatly to the success of the project.