2013 Annual Report
1a.Objectives (from AD-416):
1. Determine if late season foliar N applications can increase grape berry N concentration, content fermented wine flavor compounds.
2. Compare conventional soluble synthetic N sources to soluble organic N sources for their suitability to supplement grapevine nutrition with late season foliar applications.
3. Evaluate the effect of late season foliar N application on plant N concentration (fruit, leaves, petioles) as well fruit amino acid concentrations and other secondary metabolites (e.g., phenolics) which may have health benefits to the consumer.
4. Evaluate the effect of late season foliar N application on canopy vigor.
1b.Approach (from AD-416):
Two vineyards, Merlot (red) and Riesling (white), will be identified. The vineyards will be well established (>9 years old), managed with regulated deficit irrigation and trained to a bilateral cordon. Replicated plots will be established in each vineyard.
Rows will be chosen so that there are no missing vines in each plot. A single rate of liquid urea will be used for the conventional N fertilizer, since it is readily absorbed, does not burn, and provides only N. Materials will be applied weekly for 5 different applications beginning at veraison and ending in mid-September. To evaluate any influence of nutrient solution run-off from plant leaves, pans will be placed under the canopy in a known area during the spray events and the amount of run off collected and extrapolated to the plot size. Blade and petiole samples will be collected, prior to foliar spraying, at bloom and veraison in the second year to determine if the previous year’s foliar treatments influenced plant N concentration. Yield, plant nitrogen measurements, and harvest fruit quality data will be analyzed using Analysis of Variance (ANOVA) as the plot design is a randomized complete block design. Fermentation rate data will be analyzed as a time series. For secondary metabolites and phenolic compounds, relationships to in field treatments will be evaluated through the use of traditional ANOVA and regression analysis as well as principle component analysis to evaluate any changes in composition related to N treatments.
This research was conducted in support of objective 1 "Determine effects of water management on wine grape productivity and fruit maturity" of the parent project. In a separate study, two seasons of trials comparing 15 lb/A (17 kg/ha) of N applied as foliar materials to both Merlot and Riesling grape were completed in 2009 and 2010. For this study, data was used from those trials, but limited to Riesling grape. Additionally, rates were increased to include 0, 15, or 30 lbs/A (0, 17, 35 kg/ha) N either as foliar or soil applications. In both studies, conventional and organic N fertilizers were utilized. In addition to assessing the impact of the treatments on grape yeast assimilable N (YAN), plus yield and cluster size, plant vigor was also assessed using shoot mass measurement.
There were slight differences by year in these studies. The most effective treatment at increasing N was the foliar application of conventional N fertilizer, with a linear increase in YAN with increasing rate. Wine was made from the grapes and sensory analysis is ongoing. Upon completion a final report will be prepared and submitted.