Wine Grape Canopy Management Practices in the San Joaquin Valley
This report concludes a study conducted in the San Joaquin Valley toward determining the most effective vine training and pruning system 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 compared 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 were compared with French Colombard and Barbera. 1995 was the third year of a 3-year study. The treatments included: bilateral (Bilat) and quadrilateral (Quad) cordon training under both hand (Hand) and machine (Mach) pruning; and minimal pruning (Minimal Pruning/Cordon Training = MPCT) is also being compared with and without hedging to adjust crop load after fruit set (MPCT-Adjust). 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 form the bilateral cordon pruning treatments and MPCT Adj. in French Colombard and the hand pruning treatments in Barbera. Thus, the most restrictive pruning level (hand) and vine canopy training (bilateral cordon) systems still tend to be the most limiting to yield. Fruit composition effects from treatment in French Colombard were minimal except for a 2-week or more delay in harvest from MPCT. The bilateral cordon systems, whether hand or machine pruned, were restrictive in overall yield potential. Also, there were no advantages in the MPCT system over quadrilateral training or machine pruning. Adjusting crop load after fruit set in MPCT did not respond favorably; it reduced yield while not improving fruit composition. Overall, the data indicate the greatest advantages with quadrilateral cordon training in this vigorous cultivar. Machine pruning also showed benefit in increasing yields in some years with no adverse effects on fruit ripening or composition. 38 Barbera was most responsive to machine pruning, with large yield increases over hand pruning. While there was some delay in fruit ripening (10-15 days) from machine pruning the berries reached comparable fruit composition on their respective harvest dates. MPCT pruning showed no improved yields over machine pruning and ripened later with lower berry skin anthocyanin. Additionally, MPCT Adj. did not show any benefits from crop load adjustment after fruit set. The hand-pruned systems produced some trade-off effects. While there was higher anthocyanin in Quad Hand fruit Bilat Hand resulted in the most bunch rot. Overall, quadrilateral cordon training was the most favorable system for French Colombard and with the advantage that it could be machine pruned without affecting fruit composition. Barbera responded favorably to quadrilateral training when hand pruned but the greatest yield increase was from machine pruning, although with some delayed fruit ripening (2 out of 3 years). The MPCT treatments have been disappointing. While they may reduce or eliminate pruning costs, fruit ripening was delayed by two weeks or more and with lower fruit anthocyanin (Barbera). Adjusting crop load in MPCT after fruit set is not producing favorable crop thinning effects. This is not surprising, as the supportive shoots and leaf canopy are removed with the clusters.