James Moss, Tony Wolf,* Amanda Stewart, and Sihui Ma 
*Virginia Polytechnic and State University, 595 Laurel Grove Rd, Winchester, VA 22602 (vitis@vt.edu) 

Vineyards in the eastern United States are often characterized by excessive vegetative growth. Cover cropping is a common strategy to reduce vine vigor. Cover crops provide a myriad of agronomic benefits, but can compete for water and nutrients. Many cover-cropped eastern vineyards experience low vine tissue nitrogen and depressed berry yeast assimilable nitrogen (YAN). Low vine tissue and juice nitrogen can have negative impacts upon fruit yield and wine aroma, respectively. Previous research indicated that soil-applied nitrogen was effective at improving vine capacity and tissue nitrogen, but foliar urea was most effective at improving berry YAN. Foliar- and soil-applied nitrogen treatments were imposed upon three commercially managed sites planted to Petit Manseng, Sauvignon blanc (Vitis vinifera), and Vidal blanc (Vitis spp.). Treatments were imposed at the Sauvignon blanc site for five years. The Petit Manseng and Vidal blanc were subjected to treatments for two years. Petiole nitrogen and leaf chlorophyll content were significantly increased by soil nitrogen amendments. Soil-applied nitrogen was more effective at increasing crop yield and pruning weights than was foliar-applied nitrogen. Yields improved in the long-term experiment after four years of application. In the Sauvignon blanc vineyard, fruit:pruning weight ratios decreased with increasing rates of soil-applied nitrogen. Enhanced point quadrat analysis indicated that nitrogen treatments had no effect upon canopy architecture. Foliar urea sprays were very effective at increasing juice YAN and did not significantly alter the ammonia:primary amino nitrogen ratio. Foliar urea significantly increased most individual amino acids measured. However, foliar urea treatments were least effective at increasing individual amino acids in Vidal blanc. A nitrogen management strategy comprising both soil and foliar applied nitrogen may be the most effective means to maintain vine and must nitrogen status, while retaining the benefits of a cover crop.

Funding Support: National Institute of Food and Agriculture, US Department of Agriculture, under agreement No. 2010-51181-21599