Watson Training System for Bunch Wine Grapes

Introduction

There are two main trellising system categories: divided and single canopy. Jerry Watson, a grape grower and owner of Austin County Vineyards in Cat Spring, Texas, developed the divided-canopy "Watson system" in 2002 to solve some issues he was having with bunch rot management and harvest inefficiency in his 'Blanc du Bois' and 'Lenoir' vineyards. By adding a series of crossarms and catch wires to his highwire system, Jerry was able to improve spray penetration to the fruit zone and increase picking efficiency at harvest. The Watson hardware and wires separate clusters from the canopy foliage and may limit cluster touching compared to a standard single-high-wire system. The Watson system has been employed in the southeastern United States and can be found as far west as California. The Watson system is currently used for training hybrid grape cultivars, such as but not limited to ‘Blanc du Bois', ‘Norton', ‘Lenoir', ‘Lomanto', ‘Crimson Cabernet', and ‘Villard blanc'. A high-wire-trained vineyard, such as those often planted with hybrid wine grape cultivars, could be retrofitted to Watson training with success.

Structure, Design, and Relative Cost

The Watson system employs a divided canopy that promotes grapevine vegetative growth out and over to "rest" on trellis catch wires without requiring intensive training. Canopy division is aided by a 4-foot-wide crossarm with two wires on each side to guide the shoot growth outward (Figure 1). The Watson crossarms have a 120-degree angle that promotes the "sprawl" nature of the divided canopy (Figure 2). Five total wires are necessary to train the Watson system: one cordon wire at approximately 5 to 6 feet (60 to 72 inches) above the ground, two catch wires placed 12 inches from the fruiting wire, and two catch wires placed 24 inches from the fruiting wire. An additional wire will be needed if drip irrigation is desired. Table 1 shows the estimated cost per acre of hardware for establishing popular single- and divided-canopy trellising systems. The use of crossarms for divided-canopy systems increases the cost compared to a standard high-wire system. Note that a decreased distance between rows will increase trellis system costs per acre (e.g., by spacing the Watson system at 11 feet as opposed to 12 feet).

*Without an irrigation wire.
**Based on metal T-posts. Pressure-treated lumber posts would increase the cost per acre.
*** All costs were calculated on a per-acre basis, with a 6-foot between-vine spacing and 24-foot post spacing within the row, and do not include labor, end post structures, or other variable costs.

Due to the separated fruit zone created by the Watson system (Figure 3), there is greater potential for increased air movement through the fruit zone and increased spray coverage on fruit when compared to the standard single-high-wire system. The Watson system is hedged, or "skirted," throughout the season by hedging the bottoms of the shoots at roughly waist height (3 feet above the ground) to encourage airflow and spray penetration into the fruit zone.

Pruning, Training, and Management

In years one and two, the goal is to train the vines with a trunk and cordons per recommended vineyard establishment protocol (Reynolds and Wolf 2008). During the following two years, vine training is refined for the intended trellising system. In commercially mature vines trained to the Watson system, shoot growth extends upward and outward (toward the vineyard alleys) beyond the top wires of the crossarms and then drapes downward (Figures 4 and 5). The cordon height and separation of the fruit zone through the offset spurs can aid in efficient hand harvesting of the crop (Figure 6; see also Figure 3). The Watson system cannot be mechanically harvested with standard over-the-row harvesting machines due to the size of the crossarms. However, research is in progress to evaluate adapting the Watson system to enable mechanical harvest.

The Watson system is cordon trained to a wire placed at 5 to 6 feet above the ground. The Watson system employs spur pruning. An average of four buds per linear foot of row are retained when spur pruning in nondivided, single-canopy training systems such as the vertical-shoot-positioned (VSP) system (Table 2). Greater bud densities per linear foot of row may be retained in the Watson system due to the vertically offset angles of the spurs (see Figure 6). The horizontal canopy division created at the cordon results in spurs (and consequently, shoots and clusters) that are spaced farther apart relative to a nondivided system with inherent space limitations within the fruit zone (see Figures 5 and 6). Once the well-trained, divided shoots of the divided canopy become dormant canes and are pruned to the desired density, the resulting spurs are already positioned in the desired vertically offset angles. The increased space between clusters and shoots in the Watson system is anticipated to improve air movement and reduce bunch rots relative to nondivided high-wire systems in which fruit zones are often highly congested. Thus, depending on production goals and cultivar, roughly six to eight buds per linear foot of row may be retained when spur pruning vines trained to the Watson system (see Table 2). Different vineyard management techniques are required in Watson compared to other popular training systems, as outlined in Table 2. Variable management will result in different labor costs over the course of the growing season, during harvest, and during the dormant season.

Harvest Parameters

A study in Texas compared ‘Blanc du Bois' productivity as affected by Watson, VSP, and high-wire quadrilateral cordon training systems. Harvest parameters include crop yield and grape maturity. Comparable fruit maturity was observed in ‘Blanc du Bois' grown on both Watson and VSP in the Rio Grande Valley of Texas (data not shown). The same study found an average 52 percent increase in crop yield in Watson compared to VSP over three years; however, quadrilateral cordon (similar to a Geneva double curtain, GDC) produced greater crop yield than Watson (Table 3). A training system study in Georgia compared Watson, VSP, and GDC. In the third leaf (2015), Watson and GDC produced comparable crop yields, which were an average equivalent of 2.9 more tons of crop per acre than VSP (Table 4). Watson produced fruit with numerically greater Brix values relative to both VSP and GDC in that year. In the fourth leaf (2016), GDC produced an equivalent of 1.6 more tons of crop per acre than Watson and an equivalent of 3.5 more tons of crop per acre relative to VSP. In 2016, juice Brix values were again numerically greatest in Watson relative to VSP and GDC, but to a lesser extent than in 2015. Please note that data in Tables 3 and 4 are based on row spacing within those experimental vineyards. Planting vines trained to VSP at more representative commercial row spacings (e.g., 9 feet, as described in Table 1) would potentially have resulted in crop yields of 5.2 and 5.6 tons per acre in 2015 and 2016, respectively. This is a good lesson about row spacing and how it can greatly affect crop yield per unit land; this also demonstrates the versatility in vineyard design with the VSP system.

Considerations for Modification and Cultivars

One obvious drawback to the Watson system design, as described herein for the original version of the system, is the need to space vines farther apart between rows in order to accommodate the passage of some vineyard equipment. This vineyard design limitation is due to the 24-inch-long crossarms that extend from posts into rows in both directions. One design modification could be to use shorter crossarms for those wishing to employ the Watson system in narrower rows (e.g., 10 or 11 feet), whether in a newly planted vineyard or one where a trellis retrofit is desirable. Using shorter crossarms would likely improve fruit zone structure compared to the single-high-wire system. However, compared to the 24-inch crossarms of the original Watson design, it's easy to see that fruit zone space and canopy separation would be reduced. The question becomes "what crossarm length is too narrow (where benefits are reduced)?" and should be informed by observations of light interception, fungal disease management, fruit quality, fruit production, and harvest efficiency, among other practical considerations.To date, Pierce's disease-tolerant cultivars (‘Blanc du Bois', ‘Norton', ‘Lenoir', etc.) have primarily been trained to the Watson system in the eastern United States. However, a high-wire-trained vineyard, such as those often planted with hybrid cultivars commonly grown in Pennsylvania (e.g., ‘Chambourcin', ‘Seyval blanc', ‘Vidal blanc', ‘Traminette', ‘Noiret', ‘Frontenac', ‘LaCrescent', ‘Marquette') could be trained originally or retrofitted to Watson training with success. Vitis vinifera cultivars with a relatively trailing growth habit (e.g., ‘Petit Verdot') and those that often have weaker tendrils (e.g., ‘Merlot') may be good case studies for training on the Watson system. Future research should evaluate the performance productivity of additional hybrid and Vitis vinifera cultivars grown on the Watson system.

Crop yield was measured on a per-vine basis but extrapolated to a per-acre basis based on vine by row spacing. Vineyard was planted in 2009.

Crop yield was measured on a per-vine basis but extrapolated to a per-acre basis based on vine by row spacing. Yield is an average across four cultivars: 'Blanc du Bois', 'Lenoir', 'Norton', and 'Villard blanc'. Vineyard planted in 2013.

Summary

The Watson training system was developed by making intuitive, practical changes to the standard high-wire training system. The Watson system gives the fruit zone structure and uniformity and improves the separation of fruit and foliage. The hope is that this simple trellis structure modification to the high-wire system results in better vineyard management, improved spray penetration to the fruit zone, and greater harvest efficiency. We do not report on any of these assumptions, so the information in this fact sheet should be considered and implemented if the concept of design and practice is desirable in your vineyard. Bruce Cross, a vineyard and winery owner in Bremen, Georgia, credits the Watson system as easier to manage relative to the GDC system, particularly in terms of shoot training and harvesting. Cross stated that "while the Watson system reduces vine planting density per unit land compared to non-divided systems (e.g., VSP), the crop yield increase per Watson-trained vine can offset that reduction in planted vine number" (personal communication, 2019). The Watson system has disadvantages in terms of upfront costs, the inability to mechanically harvest, the increased between-row spacing required for installation, and the potential requirement for overhead bird netting. However, potential benefits of the Watson system, such as crop yield and management efficiency, may offset those disadvantages. For this reason, the Watson system may be worthy of consideration in some commercial vineyard situations.

References

Personal Communication with Bruce Cross of Trillium Vineyards, 2019.

Reynolds, A., and T. K. Wolf. 2008. "Pruning and Training." In Wine Grape Production Guide for Eastern North America, edited by T. K. Wolf, 124–34. Ithaca, N.Y.: Natural Resource, Agriculture, and Engineering Service (NRAES) Cooperative Extension.

Adaptation

Fact sheet adapted from originally published University of Georgia Extension Bulletin 1522, "Watson Training System for Bunch Wine Grapes," by Rachael White, Paula Burke, Fritz Westover, Justin Scheiner, Jason Lessl, Daniel Jackson, Rachel Itle, Bruce Cross, Jerry Watson, and Cain Hickey.

Prepared by Cain Hickey, Penn State Extension Horticulture: Viticulture and Enology.