Chapter 10

Vineyard Canopy Management

Techniques for Vineyard Canopy Management

Very few grapevine canopies fall within the preferred range of the parameters that characterize the ideal canopy. In areas with deeper, often somewhat fertile soils, normally abundant rainfall, and a long growing season, these factors combined with the vine’s natural vigor, may lead to very vigorous vines, often with very dense canopies. Excessive fertilization and/or over irrigating may also result in excessively dense canopies. When this is the case, canopy management techniques such as shoot positioning, shoot thinning, hedging, leaf removal, and cluster thinning may help in opening-up the canopy to expose the fruiting and renewal zones of the canopy to better illumination and air movement. These practices can have a significant impact on fruit quality and vine productivity both in the year they are applied and in subsequent years. If the canopy is naturally dense year after year, it may require changes in the trellis system to alleviate some of the crowding.

Shoot Positioning

Shoot positioning is another important element of canopy management in the vineyard. Proper shoot positioning results in orienting shoots to create a uniform distribution of foliage that minimizes shading of fruit. An added benefit of shoot positioning is that it makes other canopy management chores, such as hedging and leaf removal, easier to accomplish. It also improves the efficiency of operations such as pruning. Not only is shoot positioning important for the current growing season, it also has an impact on productivity by encouraging the development of more fruitful buds for next year’s crop.

Shoot Thinning

The first of the canopy management practices to be utilized at the start of the season is shoot thinning. Shoot thinning can be used to help improve light penetration and air movement through a canopy, adjust crop load (by thinning fruitful shoots to reduce the crop), and increase the leaf-area-to-crop ratio (by thinning non-fruitful shoots). Shoots from the base of spurs, multiple shoots from the same node, shoots growing from non-spur positions or originating in the head region or on the trunk are all candidates for removal, unless needed to replace an old or poorly positioned spur or an old cordon.

Impacts on Fruit Quality

Shoot thinning has been shown to result in higher Brix and pH in fruit and sometimes results in an increase in berry skin phenolics and anthocyanins.

Mechanized Shoot Thinning

Cordon brushes (See Figure 10.1) are used in the removal of unwanted shoots from cordon-trained vines.

Hedging

The goal hedging is to remove excess primary and lateral shoot growth from the top and sides of the canopy. This is needed to prevent shading and entanglement of shoots between vine rows and to allow worker and tractor traffic through the vineyard. Although hedging decreases canopy by cutting primary and lateral shoots, it does not directly decrease the vine’s inherent vigor and can further promote growth by inducing lateral shoot growth in vigorous vines when conducted in early to midsummer.

Impacts on Fruit Quality

As with shoot thinning, hedging shows variable impacts on fruit quality, including a potential alteration of yield, Brix, pH, and titratable acidity.

Leaf Removal

Leaf removal is typically conducted in and around the cluster zone to allow varying levels of sunlight exposure and airflow. The objective leaf removal is to have an average of one to two leaf layers remaining in the fruit zone after the leaves have been pulled. The goal is not to completely strip all the foliage from around the fruiting zone, but to provide between 40 and 60 percent exposure of the clusters (Allen, 2011). An adequate number of leaves must remain on the shoot to produce carbohydrates to support vine growth, fruit development and ripening, develop overwintering reserves and to allow vine shoot and bud winter hardiness. This can be accomplished by removing a relatively small number of leaves from the vine in the area around the fruit clusters, usually. Restrict leaf removal to those leaves positioned at or below the cluster on the shoot since those above the shoot are the primary source of carbohydrates for the developing cluster (Cantacuzene, 2007).

Impacts on Fruit Quality

By directly reducing the leaf layer number in the fruiting zone, leaf removal creates a much more favorable microclimate within the canopy enhancing the quality of the fruit. Better sunlight exposure of the clusters leads to a warming of the berries, which enhances the sugar content while reducing pH and titratable acidity, especially malic acid.

Mechanized Leaf Removal

There are two basic approaches to removing leaves mechanically from the grapevines. The first approach uses a high pressure air stream which is directed at the canopy through rotating nozzles (See Figure 10.3). The nozzles serve to deliver air blasts, which shred the leaves and/or blow them from the fruit zone leaving only petioles and veins.

Cluster Thinning

Cluster thinning is a practice used to adjust fruit yields to obtain balance between fruit and canopy to achieve optimum ripeness. Crop thinning can be used to remove undersized, poorly set or immature clusters. It can also be used to reduce bunch rot in tight-clustered varieties like Chenin blanc too.

Impacts on Fruit Quality

Crop thinning, when warranted, can help ensure that the fruit obtains adequate ripeness (Brix, pH, and titratable acidity).

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