Proper vine management practices such as balanced pruning, shoot and sometimes cluster thinning and shoot positioning will help to achieve the right interactive balance between fruit load and vegetative vigor. A good fruit load will keep vine growth in check but over cropping will cause uneven ripening, poor color development, decreased sugar content and decreased malic acid content. Conversely, leaving too few buds will force excessive vigor in the remaining shoots but these vigorous shoots typically do not produce very productive shoots the following year. Shoot positioning is beneficial for any vines trained to a Geneva Double Curtain or for any vines that tend to grow parallel to the trellis. Dr. Fiola stresses that strict nutrition management will help to keep the vine under control and promote consistent fruit quality.
Excessive nitrogen encourages high vegetative vigor, which causes a dense canopy to be produced.
Dense canopies are characterized by many shoots that produce small numbers of weak clusters the following year. Dense canopies are heavily shaded, have poor air movement and the fruit developing in those canopies stays warmer at night. These conditions combine to produce fruit of variable quality. If vegetative vigor is excessive, annual nitrogen rates should be reduced and application should be delayed until after fruit set. Keep potassium levels in the right range because adequate potassium is necessary to maximize cold hardiness but high potassium promotes high pH and high TA fruit.