TY - JOUR T1 - Nitrogen Status and Fermentation Dynamics for Merlot on Two Rootstocks JF - American Journal of Enology and Viticulture JO - Am. J. Enol. Vitic. DO - 10.5344/ajev.2013.12065 SP - ajev.2013.12065 AU - Christine M. Stockert AU - Linda F. Bisson AU - Douglas O. Adams AU - David R. Smart Y1 - 2013/02/26 UR - http://www.ajevonline.org/content/early/2013/02/20/ajev.2013.12065.abstract N2 - Adequate yeast assimilable nitrogen (YAN) levels in grape juice are necessary for yeast cells to complete fermentation to dryness. Nitrogen (N) uptake by grapevine roots varies seasonally, therefore environmental conditions and cultural practices can affect grapevine N status. In addition, genetic differences between rootstock cultivars can influence root dynamics, and subsequently N uptake, canopy biomass and finally, fruit composition. Two rootstock cultivars, 1103P and 101-14 Mgt, were fertilized with nitrogen (N) during spring or fall or received no treatment. Vine biomass, leaf N concentration, fruit composition, juice amino-N levels and fermentation kinetics were measured. The rootstock 1103 Paulsen (Vitis berlandieri × V. rupestris cv. 1103P) has a root system that tends to produce large canopies and high shoot growth. The other rootstock, 101-14 Millardet et de Grasset (V. riparia × V. rupestris cv. 101-14 Mgt), has a root system associated with smaller canopies and moderate shoot growth. The scion Merlot (V. vinifera L. cv. Merlot clone 1) was grafted onto the two rootstocks in an experimental block in Oakville, CA. Merlot on 1103P rootstock had higher YAN levels and completed fermentation faster compared to Merlot on 101-14 Mgt. Differences in fermentation kinetics were observed within rootstock N treatments that were not explained by YAN levels, indicating that other factors related to N metabolism may play important roles in fermentation dynamics. The data indicated that Merlot grown on 1103P in the Napa Valley may require little to no N supplementation while Merlot on 101-14 Mgt may require N supplementation to avoid slow fermentations. ER -