Is vigour-based length adjustment during permanent cordon establishment a beneficial practice?

Abstract

Low vigour canes selected for the establishment of permanent cordon arms may lack the sufficient vigour required for uniform bud burst and growth of new shoots following cordon training. This may lead to stunted or missing spur positions, particularly in the middle of new cordon arms where the effect is most pronounced due to the prioritisation tendencies of the vine, including apical dominance and acrotony. A trial was performed to investigate the benefits of adjusting the length of newly trained canes intended as permanent cordon arms during their establishment to limit their bud number and guide new growth. This length adjustment was based on an assessment of the apparent vigour of selected canes and was performed at the start of the first season of cordon growth, with cordons then extended to their final length. The trial did not yield results indicating a long-term beneficial response to this practice, with physiological measurements including pruning weight showing no difference between length adjusted and control vines in the later seasons of the trial. There was also a lower plant area index (PAI), and higher canopy porosity (Φ) observed in length adjusted vines compared to control vines at several points. There was no difference observed in circumference measures of the distal portion of arms which had undergone a length adjustment, suggesting that the exercise did not have an adverse impact on their capacity for transport and reserve storage. Harvest yield components did not vary with treatment; however, a significantly lower pH was observed in length adjusted vines compared to control vines in the trial's final season. Further research could help to provide more insight into the benefits of this practice, as some results from the trial, including a significantly higher pruning weight, cane number, and cane weight observed in the intermediate sections of cordon arms during the first season of growth suggest that it may have been of some aid to the cordons on which it was implemented.