Determining the Impacts of Dormant Pruning Methods and Nitrogen Fertilization on Pinot Noir Bud Fruitfulness and Yield

This research evaluated the impacts that dormant pruning and nitrogen (N) fertilization have on bud fruitfulness and yield of Pinot noir through two separate experiments over two growing seasons and three dormant periods. The research was conducted to better understand yield limitations and potentially improve yield uniformity across years, as this is an issue for producers in the cool climate of Oregon’s Willamette Valley. Oregon Pinot noir producers use primarily cane rather than spur pruning, as they believe Pinot noir does not have fruitful basal buds and will result in low yields. With the increasing need for mechanization, growers are interested in spur pruning. A ten-year-old vineyard was used for an experiment comparing cane- and spur-pruned vines for dormant bud fruitfulness, fruitfulness in spring, canopy growth, yield, fruit ripeness at harvest, and dormant pruning weights from Feb 2017 to Feb 2019. Results show that basal buds of Pinot noir are fruitful and that cane and spur-pruned vines had similar vine growth, pruning weights, yield, and fruit composition at harvest. However, spur-pruned vines had ~20 g smaller clusters, but there were no differences in berry size. Results of this study show that spur pruning Pinot noir is possible without yield loss or differences in fruit ripeness at harvest.

A separate experiment was conducted to evaluate N fertilization compared to control (no fertilization) in two vineyard blocks in 2017 and 2018. One block (Block 1) was used to evaluate legacy effects of N-fertilization applied two years prior to the data collection year compared to control vines that were not fertilized during that time. A second vineyard block (Block 2) was evaluated for concurrent effects of N-fertilization from Jan 2018 to Feb 2019 on a lower N status block that had been treated with N fertilization (or control) in the 2017 and 2018 crop years. The evaluation of the legacy block (Block 1) found greater numbers of floral primordia and greater primordia size in canes of higher vigor, regardless of N treatment after two years of N supplementation. However, there were no clear differences in vine growth or yield as a result of the prior years of N treatment. The concurrent analysis of N-fertilization on yield potential (Block 2) showed greater floral primordia numbers and size in buds of the N treatment compared to the control. There were also increases in fruitfulness in spring and larger inflorescence size (more flowers per inflorescence) in the N treatment. Véraison leaf blade N correlated with fruitfulness and inflorescence primordia size in Block 2. Yield may have increased in the block with concurrent N application; however, there were no differences in yield by harvest due to commercial thinning practices. These results suggest that modest N-fertilization of vineyards with moderate-low N status may improve yield potential without causing excessive vine growth.

Dormancy Management Practices for Central Coast Wine Grape Vineyards

Insufficient winter chilling is a localized problem in several wine grape vineyards in the south-central coast of California. Shoot and cluster numbers per vine, as well as fruit development uniformity, are often reduced as a result. A factorial experiment was conducted in 1999 to examine the interaction between pruning date and chemical treatment on the budbreak of Chardonnay and Pinot noir grapevines grown at a low chill site. Main plots within each cultivar consisted of two pruning dates: early January (5 January) and late January (22 January); sub-plots consisted of the following chemical treatments: untreated control; 2%hydrogen cyanamide (4%Dormex); 0.5%hydrogen cyanamide (1%Dormex) + 2%Agridex (a non-ionic, paraffin based surfactant); and 35%calcium ammonium nitrate (CAN-17) + 2%Agridex. Vines of both cultivars pruned in early January commenced growth in mid-February, several weeks ahead of vines pruned in late January. Budbreak was relatively uniform regardless of time of pruning, and pruning date had no significant effect on the maximum observed budbreak of either cultivar. When vines were pruned in early January, all chemical treatments advanced budbreak compared to the control. Chemical treatments had less effect on budbreak when vines were pruned in late January. Chemical treatments had little effect on the shoot number of Chardonnay vines, but vines treated with 4%Dormex had greater cluster numbers compared to vines treated with 1%Dormex + 2%Agridex and 35%CAN-17 + 2%Agridex. However, chemical treatments also advanced bloom into a period of less favorable weather conditions for fruit set and resulted in a significant reduction in yield compared to the control. Chemical treatments had little effect on shoot and cluster numbers of Pinot noir. Fruit composition was similar among the treatments in both cultivars.

Dormancy Management Practices for Central Coast Wine Grape Vineyards

Erratic budbreak due to insufficient winter chilling has been observed in several wine grape vineyards located in the south-central coast of California. Shoot and cluster numbers per vine, as well as fruit development uniformity, are often reduced as a result. A factorial experiment was initiated in 1998 to examine the interaction between pruning date and chemical treatment on the budbreak of Chardonnay and Pinot noir grapevines in this region. Main plots within each cultivar consisted of two pruning dates: early January (6 January) and late January (20 January). Sub-plots consisted of the following chemical treatments: untreated control; 2%hydrogen cyanamide (4%Dormex); 0.5%hydrogen cyanamide (1%Dormex) + 2%Agridex (a non-ionic, paraffin based surfactant); and 35%calcium ammonium nitrate (CAN-17) + 2%Agridex. Vines of both cultivars pruned on 6 January commenced growth in mid-February, several weeks ahead of vines pruned on 20 January. Budbreak was relatively uniform regardless of time of pruning, and pruning date had no significant effect on the maximum observed budbreak of either cultivar. When vines were pruned on 6 January, all chemical treatments advanced budbreak compared to the control. In contrast, chemical treatments had less effect on budbreak when vines were pruned on 20 January. Chemical treatments had little effect on shoot and cluster numbers per vine, or on the uniformity of fruit development. The results indicate that pruning timing and dormancy-breaking chemical treatments had little effect on vine performance during the high chill winter of 1998.

Dormancy Management Practices for Central Coast Wine Grape Vineyards

Erratic budbreak due to insufficient winter chilling has been observed in several wine grape vineyards located in the south-central coast of California. Shoot and cluster numbers per vine, as well as fruit development uniformity, are often reduced as a result. A factorial experiment was initiated in 1998 to examine the interaction between pruning date and chemical treatment on the budbreak of Chardonnay and Pinot noir grapevines in this region. Main plots within each cultivar consisted of two pruning dates: early January (6 January) and late January (20 January). Sub-plots consisted of the following chemical treatments: untreated control; 2%hydrogen cyanamide (4%Dormex); 0.5%hydrogen cyanamide (1%Dormex) + 2%Agridex (a non-ionic, paraffin based surfactant); and 35%calcium ammonium nitrate (CAN-17) + 2%Agridex. Vines of both cultivars pruned on 6 January commenced growth in mid-February, several weeks ahead of vines pruned on 20 January. Budbreak was relatively uniform regardless of time of pruning, and pruning date had no significant effect on the maximum observed budbreak of either cultivar. When vines were pruned on 6 Januaiy, all chemical treatments advanced budbreak compared to the control. In contrast, chemical treatments had less effect on budbreak when vines were pruned on 20 January. Chemical treatments had little effect on shoot and cluster numbers per vine, or on the uniformity of fruit development. The results indicate that pruning timing and dormancy-breaking chemical treatments had little effect on vine performance during the high chill winter of 1998.