Cordon-trained, spur-pruned vines often experience developmental delays at the mid-cordon arm positions. The delay in budbreak, shoot growth, and cluster development often translates into significant variation in the timing of cluster ripeness near harvest. The main objective of this research is to determine the role of bud number and pruning technique in minimizing developmental variation at the head-, mid-, and end-cordon positions of a vine. This study was conducted in a Cabernet Sauvignon vineyard in Oakville, California, on bilateral cordon-trained, spur-pruned vines on 6 x 8 foot spacing. Vines were pruned to either one- or two-bud spurs, for a total of 12 or 24 buds per vine, respectively. Light interception at the fruiting zone was measured via an Accupar LP-80 photosynthetic radiation sensor and then normalized by removing leaves in the denser, two-bud spur treatments. In addition to shoot length, diameter, percent berry set, berry maturity indices, spur diameter, and pruning weights, the timing of key phenological stages was tracked. Significant variation was found among shoot lengths of each treatment and among positions along the cordon. Middle positions had significantly less shoot growth than either the head or end positions, and one-bud pruning gave longer shoot growth than two-bud pruning. These study results will be used to make pruning level and vine training recommendations that will balance productivity across the vine, regardless of arm positioning.

Funding Support: California State University Agricultural Research Institute