Influence of retained node number on Sauvignon Blanc grapevine vegetative growth and yield
Background and Aims
The potential yield of grapevines is often inexpensively manipulated by altering the number of nodes retained per vine after pruning. In the context of Sauvignon Blanc in Marlborough New Zealand the influence of node number on grapevine performance is not well documented. To address this void a multi-year field study examined the effect of node number on Sauvignon Blanc grapevine growth and yield.
Methods and Results
A replicated field experiment was established by winter pruning the same grapevines to 24–72 nodes per vine (two, three, four, five or six 12-node canes per vine) over a 4-year period. Increasing the number of nodes resulted in a linear increase in vine yield in 2007. In subsequent years, the yield response decreased and from 2009 onwards, increasing the number of nodes beyond 36 per vine did not increase yield. Fewer nodes per vine were associated with greater vegetative growth and cane vigour. Pre-flowering shoot length, leaf number and shoot diameter along with end of season mean cane mass were greatest in vines with fewer nodes.
The dynamic interseasonal yield responses were caused by a combination of changes in bunches per vine and bunch mass, although the contribution of each yield component altered during the course of the experiment. Changes in cane vigour and bunches per shoot (fruitfulness) suggest that they are part of the mechanisms by which vines moderate yield over time in response to altered node number.
Significance of the Study
Increasing or reducing node number per vine does not result in sustained yield increases or reductions respectively. Grapegrowers should expect the level of yield compensation to change after the first year of a change in node number. Therefore, adjustment of nodes per vine and the selection of appropriate cane vigour at pruning should be considered carefully when setting the annual yield potential of Sauvignon Blanc grapevines.