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United States Department of Agriculture

Agricultural Research Service


Location: Horticultural Crops Research

2012 Annual Report

1a. Objectives (from AD-416):
1. Determine the impact of cluster zone leaf removal in modifying microclimate for fruit quality in both high and low vigor vines. 2. Evaluate impacts of microclimate on total phenolics and anthocyanins of Pinot noir. 3. Improve the understanding of leaf pulling on formation of norisoprenoids in Pinot noir grapes and wine in relation to inherent vine vigor. 4. Link vine vigor, leaf removal and composition to sensory characteristics of wines.

1b. Approach (from AD-416):
Study Pinot noir at two distinct locations in Oregon: a vigorous, dry farmed site (Willamette Valley) and a low vigor site (Southern Oregon). These vineyards will have the same cultivar and rootstock to reduce between site variability. The experimental vineyards will be monitored for vegetative growth, vine size and microclimate of treatments. Sunlight intensity measurements of the vine canopy in the cluster zone will be taken for all treatments concurrently. Vines will be monitored for photosynthetic efficiency. Vine microclimate will be monitored for light spectral quality and temperature throughout the season. At the end of the season, cluster weights and berry weights will be obtained to determine any treatment effects on fruit size. Shoot number per vine and cluster per shoot will be recorded during the growing season. Documents Grant with Oregon State University. Formerly 5358-12210-003-14G (8/2011).

3. Progress Report:
Obtaining adequate vine balance through canopy management is critical to production of high quality fruit for wine production. High vegetative vigor is common in western Oregon vineyards and results in high canopy density and significant management inputs to achieve quality fruit production. Canopy management practices can alter vine balance, which is the level at which the vegetative growth (vine canopy) is in balance with the fruit yield, allowing the vine to support ripening of the fruit at harvest and maintaining the sustainability of vine health over time. Manipulating the two components, canopy and fruit, allows vineyard managers to manipulate balance, so we chose to study the impacts of two management practices, crop thinning and leaf removal, on vine growth response and fruit composition and quality. The real question behind understanding best management practices in the vineyard is whether grape ripening and fruit quality are being influenced more by physiological responses in vine growth and development or by microclimate modifications caused by cluster zone leaf removal and fruit thinning practices. A 3-year project began in 2010 to identify proper timing and intensity of crop thinning for production of high quality Pinot Noir fruit in the North Willamette Valley of Oregon. At the same time, a cluster-zone leaf removal experiment was initiated to determine impacts of modifying the fruit microclimate on berry composition at harvest. The goal of this work is to come up with fine-tuned canopy management practices and identify guidelines for vine balance in high vigor vineyards of western Oregon. During Years 1 and 2 of this project, we measured the impact of timing and level of fruit removal and leaf pulling on vine growth and fruit composition. Fruit thinning treatments reduced vine yield by 40 to 70% in 2010 and by 38 to 66% in 2011, compared to full-yield vines. Despite large changes in fruit yield both years, there was relatively little change in fruit composition at harvest. There was little to no difference found for sugars, acids, color or other quality compounds in 2010. However, there was an increase in sugar and anthocyanin in 2011 as a result of crop thinning and timing. The lowest crop level had the highest color concentration, but there was no difference between most of the crop thinned treatments. Sugar levels were not different when comparing the two crop thinning levels to each other, and they were only different from the non-thinned vines. Leaving higher yields until later in the season did not depress vine growth of these highly vigorous vines, thereby requiring just as much vine management (hedging, leaf pulling, etc) as earlier crop-thinned vines. Therefore, grape growers have a relatively wide window of time to adjust crop levels on Pinot Noir if thinning is required. The leaf pulling results were similar from 2010 and 2011. Leaf removal treatments resulted in differences in cluster sunlight exposure, but there were no differences in sugar, acid or color composition. There were minor differences in whole berry tannin in 2011, but it did not correlate with sunlight exposure. Removing leaves in this trial did not decrease vine growth or fruit ripening. While little difference was observed in this trial for basic fruit composition and vine growth, the impacts of leaf pulling may be beneficial for preventing disease infestation, particularly Botrytis bunch rot. Further analysis of fruit in both experiments will yield more information on the differences observed in the vineyard and the fruit at harvest. Field and lab research continues in 2012 to provide additional data from which to draw more solid conclusions and develop metrics for grape growers to make informed decisions in crop thinning and leaf removal practices which are widely used in premium winegrape production. This research was conduction in support of objective 1B, Perennial Crops of the parent project.

4. Accomplishments

Last Modified: 06/21/2017
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