Issue link: http://read.dmtmag.com/i/590163
www.goodfruit.com GOOD FRUIT GROWER NOVEMBER 2015 37 F ive years after Dr. Tom Zabadal planted his experimental two-tier cordon system for Concord grape production, it seems to be doing what he wanted—producing higher yields with- out sacrifi cing quality. Last year, it produced 8.3 tons per acre, while the system growers conventionally use yielded 3.2 tons. Brix level was 16.2° no matter which system was used. Speaking to growers at the 26th annual Viticulture Day at the Southwest Michigan Research and Extension Center in Benton Harbor this summer, Zabadal said he started his research after realizing that Concord grape growers were in for a real profi tabil- ity challenge that might last a long time. Grape prices were headed down to the low $200-per-ton range, while costs were running $1,000 an acre. "There was no prospect of better prices, so the solution needed to be higher yields," he said. He set out to change the existing system enough to get those higher yields without changing it so much that existing machinery—sprayers and harvesters—would have to be replaced. In the standard way of doing things, growers plant vines six to ten feet apart—eight feet on average—in rows about nine feet apart, and develop a trunk supporting a cordon made up of two arms that stretch along a wire at six feet. They grow plants on their own roots and seldom use grafted rootstocks. He developed the new model based on three changes. Alley width is somewhat narrower at eight feet. The top cordon wire is raised a foot, to seven feet. A second wire is added at the four-foot level, and two arms there form a second cordon trained from the same root. Each vine has four arms instead of two. Instead of producing the entire crop on one cordon at six feet, the crop is produced on two cordons at four and seven feet. "I like the Scott Henry training system as a vertically divided training system for wine grape produc- tion, and I thought this two-tier cordon training system could be a good fi t for Concords," Zabadal said. In addition, he planted the vines on the somewhat more vigorous SO4 rootstock. "You need a large vine to produce a large crop," he said. In his tests, each change added to yield. More profi ts from Experimental design doubled Concord grape yields last year. by Richard Lehnert RDS