CRAFTSMANSHIP ON THE FIELD:
The craftsmen of winemakers using the spacer springs in vineyards
The use of vine training systems in viticulture is aimed primarily to assist in canopy management with finding the balance in enough follage to facilitate photosynthesis without excessive shading that could impede grape ripening or promote grape diseases. Additional benefits of utilizing particular training systems could be to control potential vields and to facilitate mechanization of certain vineyard tasks such as pruning, irrigation, applying pesticide or fertilizing sprays as well as harvesting the grapesIn deciding on what type of vine training system to use, growers will also consider the climate conditionsof the vineyard where the amount of sunlight, humidity and wind could have a large impact on the exact benefits the training system offers. For instance, while having a large spread out canopy such as what the Geneva Double Curtain offers can promote a favorable leaf to fruit ratio for photosynthesis it offers very little wind protection. In places such as the Châteauneuf-du-Pape , strong prevailing winds such as le mistral can take the fruit right off the vine so a more condensed, protective vine training system is desirable for vineyards there.
While closely related, the terms trellising, pruning and vine training are often used interchangeably even though they refer to different things. Technically speaking, the trellis refers to the actual stakes, posts, wires or other structures that the grapevine is attached to. Some vines are allowed to grow free standing without any attachment to a trellising structure. Part of the confusion between trellising and vine training systems stems from the fact that vine training systems will often take on the name of the particular type of trellising involved. Pruning refers to the cutting and shaping of the cordon or "arms" of the grapevine in winter which will determine the number of buds that are allowed to become grape clusters. In some wine region, such as France, the exact number of buds is outlined by Appelation D' origine controlèè (AOC) regulations. During the summer growing seanson, pruning can involve removing young plant shootor excess bunches of grapes with green harvesting. Vine training systems utilize the practice of trellising and pruning in order to dictate and control a grape vine's canopy which will influence not only the potential yield of that year's crop but also the quality of the grapes due to the access of air and sunlight needed for the grapes to ripen fully and for preventing various grape diseases.
While the term canopy is popularly used to describe the leafy foliage of the vine, the term actually refers to the entire grapevine structure that is above ground. This includes the trunk, cordon, stems, leaves, flowers, and fruit. Most vine training deals primarily with the "woody" structure of the vine-the cordons or "arms" of the vine that extend from the top of the trunk and the fruiting "canes" that extend from the cordon. When the canes are cut back nearly to the base of the cordon, the shortened stub is called a "spur" Grapevines can either be cane trained or spur trained. In cane training, the grapevines are "spur pruned" meaning that in the winter the fruiting canes are pruned essentially down to their spurs with over 90 percent of the previous year's growth (or "brush" as it is known) removed. Examples of cane training systems include the Guyot, Mosel arch and Pendelbogen. Conversely, spur trained vines are "cane pruned" meaning that the individual canes are relatively permanent with only excess buds at the end of the cane being removed.
Cordons are trained in either a unilateral(one arm) or bilateral (two arms) fashion with the latter resembling the letter "T". The cordons of grapevines are most commonly trained horizontally along wires such as Lyre and Scott Henry system. However notable exceptions do exist, such as the "V" and "Y" trellis systems which elevate the cordon to various angles that resemble their namesake letter. Note that vertical trellising systems, such as the VSP system often used in New Zealand, refer to the vertical orientation of the fruit canes in an upward manner and not the cordon "arms" of the vines.
From the cordon, plant shot emerge from the bud that eventually develops mature bark and becomes the fruiting cane from which grape clusters will emerge. These canes can be positioned and trained to whatever angle is desired by the grower. Typically they are positioned upwards but they can be bent into an arch such as a Pendelbogen or Mosel arch system, or trained to point downwards such as the Scott Henry and Sylvos system. The later method requires more labor intensive trellising and training for Vitis Vinifera vines which are naturally more inclined to grow upwards rather than down. In systems such as the Scott Henry, this downward growth is achieved by the use of movable wires that first allow the canes to grow upwards until about 2 to 3 weeks before harvest when they are then shifted downwards where the weight of gravity on the hanging grape clusters helps keep the canes pointing down.
The leafy foliage of a grapevine's canopy will be dependent on the particular Grape varietyand its propensity for vigorous growth. These leaves emerge from shoots on the fruiting cane in a manner similar to the grape clusters themselves. A vine is described as "vigorous" if it has a propensity to produce many shoots that areoutwardly observable as a large, leafy canopy. The ability of the grapevine to support such a large canopy is dependent on the health of its root system and storage of carboydrates. If a vine does not have a healthy and extensive root system in proportion to its canopy, then it is being overly vigorous with parts of the vine (most notably the grape clusters) suffering due to lack of resources. While it may seem that more foliage would promote increased photosynthesis (and such carbohydrate production), this is not always the case since the leaves near the top of the canopy create excess shading that hinders photosynthesis in the leaves below. One of the objectives of vine training is to create an "open canopy" that allows limited excess leaf growth and allows plenty of sunlight to penetrate the canopy.
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