Date of Graduation

Summer 2011


Master of Science in Plant Science (Agriculture)


College of Agriculture

Committee Chair

Martin Kaps


Norton, canopy management, leaf removal, shoot positioning, fruit composition, red wine color

Subject Categories

Plant Sciences


Because of their dense nature, Norton grapevine canopies can prevent much sunlight from reaching the fruit clusters, so various degrees of canopy manipulation were implemented on Norton grapevines at Mountain Grove, Missouri. This experiment opened the canopy in attempts to improve both fruit and wine quality by allowing more sunlight to reach the clusters. Treatments included an unmanaged control, shoot positioning, removal of primary leaves directly surrounding the grape clusters, removal of primary leaves and secondary shoots surrounding the clusters, and removal of primary leaves and secondary shoots around the clusters on the north side of the canopy only. Interior canopy light, leaf layers, and foliage removed were measured and analyzed. The canopy was significantly opened with more severe manipulation. Yield showed no significant differences among treatments, but increased slightly with increased defoliation. Analyses on the juice showed significantly lower values for pH and titratable acidity in the most severely defoliated treatment. Shoot positioning and primary leaf removal caused an increase in total soluble solids. The unmanaged control and most severely defoliated treatment were processed into wine, and although there were no significant differences, the trend was toward decreases in pH and potassium and increases in total anthocyanin content and total red wine color in the severely defoliated treatment. Canopy manipulation significantly increased the amount of sunlight that could reach the clusters and showed some improvement in fruit composition and red wine components.


© Staci Nicole Bass

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