Submitted to: Oregon Wine Research Institute
Publication Type: Abstract Only
Publication Acceptance Date: March 26, 2013
Publication Date: April 2, 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. Oregon Wine Research Institute. Meeting booklet. Technical Abstract: Oregon Pinot noir vineyards are generally characterized as having low crop loads. 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 Pinot noir vineyard to assess the interaction of nitrogen status and yield on vegetative and reproductive growth. Canopy size was manipulated through vineyard floor management practices that influenced vine tissue nitrogen (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 soil treatments. The number of lateral shoots and lateral leaf area at véraison decreased 69% with the presence of grass in 2012. Stem water potential was not different between treatments across the growing season, indicating N as the limiting growth factor. Although there was an up to three-fold increase in solar radiation penetration through the canopy 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, and a range of crop load from 0.98 to 3.40 was observed. Biomass (leaf area and pruning weight) was influenced more by N status than by crop level. This work aims to further understand source-sink relationships to define an optimal balance among vegetative growth, yield and fruit quality.