Studies on the sultana vine. 4. A pruning experiment with number of buds per vine varied, number of buds per cane constant

Abstract

A pruning experiment is described in which the number of buds per vine was varied by varying the number of canes retained, the number of buds per cane being held constant. With increasing number of canes per vine, per cent. bud burst generally showed a linear decrease, and per cent. fruitful shoots, although generally not affected, showed a similar effect after years of high fruitfulness. Bunch number and weight of fresh fruit harvested increased linearly with increasing cane number. Sugar content decreased and number of mature buds produced increased with increasing cane number. Weight of fresh fruit was positively correlated with bunch number, and negatively correlated with sugar content and number of mature buds. Bunch number was positively correlated with per cent. bud burst. The yield from 10 canes in a year of low fruitfulness was no greater than the yield from 4 canes in a year of high fruitfulness. In the high year evidence suggesting overloading on vines with more than seven canes was obtained from the sugar content and bud number results. Vines returned to uniform pruning treatment after a year of high fruitfulness, the third year of the experiment, showed residual effects in the first season but not thereafter. It is concluded that by regulating the number of canes according to the potential fruitfulness found by microscopical examination before pruning, overloading can be avoided in very fruitful seasons and the crop can be improved in years of low fruitfulness. However, complete uniformity of crop from year to year cannot be achieved.