Delayed pruning to postpone ripening in Pinot noir

By Lucinda Heyns

The aim of this project was to investigate what the effect of delayed pruning is on cane pruned, trellised Pinot noir, over more than one season. Researchers also wanted to validate whether this technique can be used to preserve acidity and contain yields, especially considering sparkling wine production.

Project layout

Mature Pinot noir vines were subjected to the following pruning strategies over a period of three years:
-          Standard winter pruning (WP);
-          Double pruning (DP): In mid winter, fruiting cane and spur were selected and retained and previous season’s bearing cane removed. In spring, the cane was shortened to 10 nodes and tied to the cordon wire;
-          Late pruning (LP): All pruning operations were postponed until spring and performed in one day.
-          With both DP and LP, shoot growth from node 10 of unpruned canes reached an average stage where three leaves have unfolded before being pruned back to 10 buds.
Phenological and ripening dynamics, yield components and must composition were determined.

-          Double pruning did not affect phenology and overall vine performance compared to that of WP;
-          LP significantly delayed ripening over 2 trial years. The vines broke dormancy later and slower than WP and DP. All early phenological stages were delayed and budburst occurred 9–23 days later than WP. LP was thereby confirmed as a viable risk-management technique against frost. No significant delaying effects were seen during the first year of application, indicating that treatment application over more seasons is needed to achieve the desirable effect;
-          Late pruning induced a 35% yield reduction compared to that of WP, an effect mainly because of reduced bud fertility, lower bunch number per vine and, to a lesser extent, to smaller berries;
-          A novel result of this study in comparison to earlier work is how delayed pruning can also affect uniformity of bud development and shoot growth along the cane for the two fully monitored years. LP increased variation in phenology and shoot growth compared to WP and DP.

Significance of the study
If repeated over several seasons, late pruning applied to a cane-pruned system when the distal part of the cane has already burst an average of three leaves can become effective at delaying phenology and extending maturity into a cooler season.

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