Issue link: http://read.dmtmag.com/i/590163
38 NOVEMBER 2015 GOOD FRUIT GROWER www.goodfruit.com STANDARD TOP-WIRE CORDON TRAINING SYSTEM TWO-TIER CORDON TRAINING SYSTEM Concord grape yields double with two-tiered system A test plot with four cordons per vine instead of two increased yields—without affecting Brix levels—on plants using their own roots as well as for those grafted onto a more vigorous SO4 rootstock. 8 feet between trunks 6 feet to top wire 3 feet Standard yields Tons/ Clusters Cluster Rootstock acre per vine weight Brix Own roots 3.2 43 87g 16.2° SO4 4.6 50 110g 16.2° 8 feet between rows 4 feet 7 feet to top wire 8 feet between trunks 8 feet between rows SOURCE: TOM ZABADAL, MICHIGAN STATE UNIVERSITY JARED JOHNSON/GOOD FRUIT GROWER Two-tier yields Tons/ Clusters Cluster Rootstock acre per vine weight Brix Own roots 6.5 93 92g 16.2° SO4 8.3 95 110g 16.1° Last year, the top wire-only cordon produced 3.2 tons per acre. When the SO4 rootstock was added to that system, yields increased to 4.6 tons. When the second cordon was added without a change in rootstock, yields went up to 6.5 tons. And when the two-tier system was used with the SO4 root, yields increased to 8.3 tons per acre. The two-tier system contained more grape clusters per vine, but cluster weight did not change unless the rootstock changed. The SO4 vines produced clusters that were larger—about 110 grams per cluster compared to about 90 grams on the own-rooted vines. The number of clusters about doubled with the second cordon tier, rising from about 45 to about 90. The reason seven feet was chosen as the new height was because that's the height an over-the-row harvester can handle. "At the time we started this experiment, we could not get a taller machine," Zabadal said. Since then, a taller one has become available, he said. In developing the system, he also wants to make sure it is adapted for future mechanization. Michigan State University has also developed a mechanical shoot-po- sitioning machine, which is now being commercially produced, that combs the hanging Concord shoots downward. The system also has to fit with mechanical pruning. Will his two-tier model be sustainable into the future? "We're pretty pleased where it's at," Zabadal said. "It seems pretty decent so far, but its long-term performance is uncertain, and that's why we call it an experiment." • goodfruit.com TRUSTED More growers come to us for their news than to any other source. Shannon Dininny, Senior Editor The essential resource