Wine Grape Canopy Management Practices in the San Joaquin Valley

This work is a continuation of studies conducted in the San Joaquin Valley toward determining the most effective canopy management practices for fruit composition, quality, and yield while being cost-efficient and adaptable to mechanization. Previous work was conducted on training system and trellis designs and the effects of fruit exposure on yield and fruit composition. The current study compares pruning systems which can be mechanized and are much different in crop level, vegetative development, and canopy configuration. Six systems involving bilateral and quadrilateral cordon training and hand, machine-hedge, and minimal pruning are being compared with French Colombard and Barbera. 1993 was the first year of a 3-year study. The treatments include: bilateral (Bilat.) and quadrilateral (Quad.) cordon training under both hand (Hand) and machine (Mach.) pruning; and minimal pruning (MPCT) is also being compared with and without hedging to adjust crop load after fruit set. Generally, the treatments with the lowest pruning severity (MPCT, followed by MPCT-Adjust, Quad Mach, Bilat. Mach, Quad. Hand, and Bilat. Hand) produced the most clusters of least weight. Thus, the vines tended to adjust crop loads with smaller clusters and berries. This resulted in comparable yields from all treatments except for lower fruit weights from Bilat. Hand and MPCT Adj. in French Colombard and Bilat. Hand and Quad Hand in Barbera. Fruit composition was not affected in French Colombard except for a 2-week delay in harvest from MPCT. Thus, the Bilat. Hand treatment was restrictive in overall yield potential while there was no advantage in MPCT over machine pruning or adjusting crop in MPCT. Overall, this first year of data taking indicates comparable and most favorable fruiting responses among Bilat. Mach, Quad Hand, and Quad Mach with French Colombard. Bilat. Hand and MPCT Adj were lowest in yield and both MPCT treatments showed a 2-week delayed fruit maturation. Fruit composition was affected greatly in Barbera, especially by pruning method, with the hand pruning treatments ripening earliest followed by the machine pruning and then MPCT, much later. Overall, the two machine pruning treatments — Bilat. Mach and Quad Mach — produced the highest yields with favorable fruit composition. MPCT pruning showed no improved yields over machine pruning and ripened much later. MPCT Adj did show some crop adjustment after post-fruit set hedging with heavier clusters and a 1-week earlier fruit maturity as compared to MPCT. The Quad system out-performed the Bilat. system in yields with Hand pruning. However, Hand pruning increased bunch rot in Barbera over the mechanized systems, especially with Bilat. training. For both cultivars, machine pruning with either bilateral or quadrilateral (2′ cordon separation) might be considered the most favorable system overall in this first year. For hand pruning, the quadrilateral system is best. Additional work is needed to determine long-term effects, especially if MPCT may improve over time.