Effect of Mechanical Pruning on Yield and Quality of 'Concord' Grapes

After mechanical harvesting of 'Concord' grapes was totally implemented, the most time-consuming vineyard operation in Arkansas became pruning. Grape producers complain of decreasing availability of qualified labor for pruning and tieing, and feel that pruning should be the next operation mechanized. Single and double curtain vines were established in a 14-year-old vineyard at the Main Station, Fayetteville, and in 1971 research was begun to evaluate the effects of mechanical pruning on yield and quality of 'Concord' grapes. The cutter bar on the mechanical pruner was adjusted to prune to 4or 5-node spurs. The experiment was designed as a randomized block consisting of 2 training methods (single and double curtain) and 4 levels of nodes per vine (hand at 30+10, 60, 90, and no touch-up). On the no-touch-up treatment, any canes that were running along the wires were cut halfway between the vines when the cordons were retied. All treatments were replicated 6 times. Time required to prune each treatment was recorded. Fruit was harvested, yield was recorded, and representative samples were collected and frozen until quality could be analyzed. The rows where the 1971 test was conducted were removed from the vineyard and a 5-year study on mechanical pruning was reestablished in another section of the vineyard in 1974. There was no shoot positioning in 1971; shoots were positioned in 1974. The figure shows the time required in 1971 to prune vines to 90 and 60 buds on single and double curtain trellis systems after machine pruning, as compared to total hand pruning. Without shoot positioning, there was no saving in labor on the mechanically pruned double curtain system. However, labor was reduced considerably on the mechanically -pruned, single curtain vines, with a reduction of about half of the labor needed for the 90 node-per-vine treatment. In the 1971 test, with no shoot positioning, there was no significant difference in yield between the two training systems (see table). Soluble solids were significantly higher under the single curtain training. There was no difference in titratable acidity, but color was superior on grapes produced on the non-positioned, single curtain system.