Submitted to: American Society of Enology and Viticulture Annual Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: April 15, 2013
Publication Date: June 25, 2013
Citation: Reeve, A.L., Skinkis, P.A., Lee, J., Tarara, J.M., Vance, A.J. 2013. Shifts in fruitfulness and crop load of ‘Pinot noir’ in response to nitrogen depletion. American Society of Enology and Viticulture Annual Meeting Abstracts. P75. Technical Abstract: Oregon 'Pinot noir' vineyards are generally characterized as having low crop loads (with large canopies relative to naturally low yields). Premium ‘Pinot noir’ producers commonly reduce crop load further by fruit thinning. The long-term implications of these practices on vegetative growth, fruitfulness, fruit set, and berry quality are not fully understood for low yielding, cool-climate situations. During 2011 and 2012, a study was conducted in a commercial vineyard to assess the interaction of nitrogen (N) status and yield on vegetative and reproductive growth. Canopy size was manipulated through vineyard floor management practices that influenced vine tissue N through use of competitive perennial grass and/or tillage. Yield was manipulated as a split-plot with full and half crop levels. Petiole and leaf blade tissue samples measured at bloom and véraison each year were significantly lower in the grass treatment (lowest %N), resulting in reduced leaf area compared to tilled. The number of lateral shoots and lateral leaf area decreased 69% with the presence of grass at véraison in 2012. Stem water potential was not different among treatments across the growing season, indicating N as the limiting growth factor. Although there was an increase in canopy sunlight penetration by up to three-fold in the lowest N vines, the number of inflorescences per shoot was 11% lower than the higher N vines in 2012. The number of florets per inflorescence was reduced 10 to 35%, but fruit set increased 18 to 29%. Cane weights in the highest and lowest %N were 109 g and 55 g, respectively, resulting in a range of crop load from 0.98 to 3.40. Biomass (leaf area and pruning weight) was influenced more by N status than crop level. This work aims to further understand source-sink relationships to define optimal relationships between vegetative growth, yield, and fruit quality.