The purpose of this study was to evaluate the potential of four different cordon renewal strategies to revive a 34-year-old, declining block of Merlot. The vineyard was cordon-trained and spur-pruned but continued exposure to freeze events resulted in gradual vine decline and reduced yields.
Project layout:
Different pruning treatments were applied to a 34-year-old Merlot vineyard over three consecutive seasons:
- Cordon completely removed about 13 cm below cordon wire
- Three short canes were left per cordon and trained to the old cordon plus all other buds and spur positions were removed
- Cordon completely disbudded to encourage renewed spur positions
- Control: Standard spur pruning
Vine recovery was determined by measuring pruning weight, yield components and fruit composition.
Results:
- Retaining three canes resulted in higher average yields over a three year period, as well as cumulative yield, compared to the other treatments.
- Complete cordon removal resulted in a uniform recovery, but the first year there was no yield and during the following two years, yields were intermediate. This is not ideal from an economic perspective.
- Complete disbudding resulted in yields similar to the control. However, it also caused bushy growth in the first year, which increased canopy management costs.
- Overall fruit composition remained similar in all four treatments.
Significance of the study:
Older vineyards where productivity starts to decline need to be replanted eventually, but establishment costs are high. This may be a method to delay replanting and the capital input costs associated with it, while still achieving economically viable yields.
Reference
Pruning approaches to revive col-injured Merlot grapevines: http://wawgg.org/files/documents/2017_AM/Lynn_Mills_2016_WAWGG_Pruning_approaches.pdf
Image source: http://thegrapevinemagazine.net/article/grapevine-graft-transmissible-fungal-trunk-diseases/
