Issue link: http://winesandvines.uberflip.com/i/116287
WineEast Grapegrowing The next element to evaluate is the Grapevine Tunnel Installation Cost degree of water control desired. In the next NUMBER LENGTH width cost per total section, where I discuss how to grow grapes OF BAYS OF TUNNEL of bay square foot cost in a tunnel, you will find information about Half acre 3 303 feet/ 24 feet/ 95 cents $20,875 93 meters 7.32 meters managing the plastic skin. The skin can be rolled up or down depending on the needs Acre 6 303 feet/ 24 feet/ 80 cents $34,958 93 meters 7.32 meters of the vines. When the sides are rolled up, 2.5 acres 15 303 feet/ 24 feet/ 69 cents $75,304 water will enter the tunnel at the drip line 93 meters 7.32 meters if it rains. In many cases this type of water can be managed. However, if this is an slope. The cooler air entered the tunnel issue, there is a tunnel design (shown in Designing your tunnel layout and was warmed, repeating the cycle. In the photo on page 89) that allows for more It may seem counter-intuitive to think critical times, artificial heat can be used to control of this water. about growing grapes in a tunnel in the first create a directed airflow to prevent frost or The slope of a vineyard is not a hindrance place, let alone being able to make money freeze damage. In some cases, growers have at it, too. The physics of environmental to installing a high tunnel and, in fact, placed baffles in the tunnel to segment and control are straightforward. However, getting sloping ground can provide unanticipated the right balance of structure cost to perforslow the air down so the warmth remained benefits for tunnel consideration. Orienting mance is the key factor. in each baffled area. the tunnel along the slope line can provide The experimental vineyard described in One factor that must be taken into aca warming effect that can help save crops Part I of this series was laid out with a plant count with tunnels is the height of the during a freeze event. There are places density of 1,500 plants per acre. It should tunnel. The higher the tunnel, the lower where tunnels have been installed on slopes be noted that when vines are planted in a the wind velocity the covered tunnel will up to 20% where, on days when outside tunnel, a small amount of useable land is tolerate. Some growers have chosen to use temperatures were at or near freezing, "lost" with each bay of a tunnel system. narrow-width bays to get the height needed. the tunnels were blasting warm air out Thus, it is important to know as much as Others have chosen to use both wide bays the top of the tunnel. The infrared light possible about the objectives desired so and high tunnels and then installed windwas trapped in the tunnel, which warmed Vance_Jan11.qxp 11/23/10 9:29 AM Page 1 that you make the most efficient use of the breaks to lessen the chance of wind damage. the air; warm air rises and so it moved up space under the tunnel. Tunnel bays come in a variety of widths. Because of the cost of infrastructure, it does not make economic sense to use tunnels with a width of less than 24 feet, and there are several reasons to use wider bays. Basic Hoop Layout on page 90 illustrates row configurations for widths from 20 feet to 28 feet. Approximately 0.8-1.0 meters of clear space from the pole line toward the row on either side of the pole is needed to allow for pruning, harvesting and other activities to service the needs of both the vines and the structure. Once the bay size is determined, the frame is installed by drilling hoop posts in the appropriate spots and installing the correct cross bracing. How much bracing is needed is determined by the maximum velocity of wind the tunnel is expected to withstand before removal of the covering is demanded for structural safety. Many bays are rated to withstand up to 60 mph of sustained winds. Although tunnels can be retrofitted onto an existing vineyard, it is easier to install a tunnel prior to planting. However, only the hoops need be in place before planting begins. A grower should expect to apply the 88 W in es & V i ne s AP R I L 2 013