Practical Winery
65 Mitchell Blvd, San Rafael, CA 94903
phone: 415-453-9700 ext 102
email: Office@practicalwinery.com
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Spring 2011
GRAPEGROWING
Mechanically box-pruned Pinot Grigio had 72% higher yields, with 13% smaller berry size. This was due to a significantly greater number of shoots per foot.
Mechanically shoot-thinned treatments significantly affected yields. In both varieties, the high shoot density treatment had significantly higher yields. Although there were no differences in yield in the low and medium shoot density treatments in Syrah, the high shoot density treatment had 12% more yield. In Pinot Grigio, the yield increased significantly with each increase in shoot density treatment.
Interactions There were no effects of dormant pruning method, shoot density control, or leaf removal on the leaf area to fruit ratio of Syrah vines. This was probably due to the vigorous growth habit of Syrah, where long shoots with large leaves usually make up for the removal of shoots by shoot-thinning practices.
Shoot density and leaf removal interacted to affect the leaf area to fruit ratio of Pinot Grigio. High shoot density treatments with leaf removal did not have enough leaf area for the amount of fruit that was borne on the shoots. Conversely, vines receiving low shoot density treatments with no leaf removal had excess leaf area for the amount of fruit that was borne on the shoots.
Effect of canopy management on fruit composition Hand spur-pruned Syrah vines reached the 24° Brix target one week prior to mechanically boxpruned vines.
During ripening, Syrah vines with low and medium shoot density treatments had higher Brix than those with high shoot density treatment. However, by 24° Brix, there was no difference among the three shoot density treatments. Leaf removal did not affect harvest date.
The hand spur-pruned Pinot Grigio vines had higher total soluble solids throughout ripening, compared to mechanically box-pruned vines, and reached 22° Brix two weeks earlier. Pinot Grigio vines with low and medium shoot density treatments were harvested two weeks prior to those with high shoot density. Leaf removal delayed harvest of Pinot Grigio vines by one week.
Take Home messages
Mechanical pruning is not enough to control yield. Mechanical pruning of the vines did not give adequate control of the shoot number and production, because the
Figure 2. Shoot thinning was applied to Pinot Grigio vines using an Oxbo Cordon Brush (Model 62731) with auxiliary shoot-thinning heads. This cordon brush was mounted to an Oxbo 1210 single-row tractor-mounted tool carrier.
number of non-count shoots was equal to or more than the number of count shoots retained at pruning. Although noncount shoots are not as fruitful, they are likely the cause of overcropping, and cannot be controlled by pruning.
Mechanical shoot-thinning is needed to adequately control yield. Without accurate shoot thinning, there is potential for excessive yields. The ability to mechanically reduce the number of non-count shoots makes achieving vine balance possible through mechanized farming practices.
When vines were mechanically shoot-thinned, the medium shoot density treatment resulted in optimum shoot density for these cultivars: 7 and 10 count shoots per foot for Syrah and Pinot Grigio, respectively.
Mechanical shoot-thinning techniques can be improved. For example, the total numbers of shoots retained were different than the intended treatments for count shoot control.
The three shoot density treatments called for 7, 10, and 15 count shoots per foot and the actual numbers were 12, 13, and 17 total shoots per foot for Syrah, and 17, 20, and 21 total shoots per foot for Pinot Grigio (very difficult to thoroughly thin on a 12-inch wide T-trellis).
Integrating at least two canopy management practices ensures improvement of the canopy microclimate. Pruning alone does not adequately control canopy microclimate for either cultivar. For Syrah, integrating pruning, shoot density, and leaf removal ensures fewer leaf layers.
Leaf removal as a stand-alone practice improves PPFD and percent canopy gaps for Syrah. For Pinot Grigio, a combination of dormant pruning and shoot-thinning, or leaf removal as a stand-alone treatment, improves PPFD transmittance or percent canopy gaps. Leaf removal was the only treatment to effectively control the leaf layer numbers for Pinot Grigio.
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