Response of 'Sultana' Vines to Training on a Divided Canopy and to Shoot Crowding

9Sultana9 (syn. 9Sultanina9, 9Thompson Seedless9, Vitis vinifera L.) vines of mature age planted in rows 11 ft apart were trained to form canopies 6, 9, or 18 ft in length when spaced 9 ft in the row; vines spaced 18 ft in the row had 36-ft canopies. Canopy length greater than vine spacing was obtained by dividing the canopy into two parallel curtains, 4 ft apart. In the 9-ft canopies there were three systems of arranging the shoots to modify their exposure. In the 18-ft canopies there were four systems of arranging the shoots. All vines were pruned alike, in winter of 1967, 1968, and 1969, by adjusting the number of nodes retained to the weight of the canes, which averaged about 4 lb. per vine; then, vines with canopies 6, 9, 18, and 36 ft in length had 22, 14, 7, and 3 nodes per foot of canopy, respectively. At harvest in 1968, treatment means did not differ in yield or fruit maturity. In 1969, pruning weights, and thus node numbers per vine and per foot of canopy were similar to those in 1968. At 1969 harvest, however, the treatments did affect the yields of fresh fruit per vine; they were 7.9 kg for 6-ft canopy, 16.8 kg for 9-ft, 20.8 kg for 18-ft without foliage wire, 25.5 kg for 18-ft with foliage wire and 28.4 kg for 36-ft canopy length. This was not accompanied by reduction in fruit maturity, resulting in respective total yields of soluble solids per vine of 1.8, 3.4, 4.2, 5.0, and 5.8 kg. In 1970, differences between treatments followed the same trends but were smaller. The differences in yield were due to differences in fruitful shoots/node, clusters/node and crop weight/node. It is concluded that, in 9Sultana9, shoot crowding reduced yield and that yield increases were obtained from the vine training which reduced shoot crowding.