Miranda Ulmer, Patty Skinkis,* and R. Paul Schreiner
*Oregon State University Horticulture, 4017 ALS Building, 2750 SW Campus Way, Corvallis, OR 97331 (patricia.skinkis@oregonstate.edu)

Pruning and nitrogen fertilization are management practices that influence vineyard productivity. Cane pruning is predominant in Oregon Pinot noir vineyards, as producers fear that spur pruning will result in low yields due to a lack of basal bud fruitfulness. Nitrogen (N) fertilization is often avoided, because it is thought to create excess vegetative growth and reduce wine quality, but N-deficient vineyards often have reduced yields. Little information is available on the impacts of pruning and N fertilization on bud fruitfulness, an important predictor of yield. Two separate experiments were conducted in commercial Pinot noir vineyards in Oregon to understand the impacts of pruning method (cane and spur) and N fertilization (N fertilization and no fertilization) on fruitfulness and yield. It was hypothesized that basal nodes would be fruitful but might reduce yields in spur- compared to cane-pruned vines. It was also hypothesized that vines with low N status would have lower fruitfulness and yields. Year 1 pruning trial results indicate that basal buds have floral primordia, and similar bud fruitfulness and inflorescence primordium size were found in buds with both pruning methods. However, fruitfulness in spring was higher in cane-pruned vines. Vine growth, yield, and fruit composition did not differ between cane and spur pruning. Year 1 results of the N fertilization trial indicate that N fertilization had little impact on bud fruitfulness, fruitfulness in spring, vine growth, or yield. However, vine vigor, measured in dormant canes, was related to bud fruitfulness parameters in both experiments. In the N trial, greater bud fruitfulness was related to larger cane size (weight and internode diameter). In both trials, greater inflorescence primordia size was observed with larger internode diameter. This work will continue into 2019, and the results will help improve pruning and N management guidelines for Oregon Pinot noir producers.

Funding Support: American Vineyard Foundation