- The majority of grapes grown in Oregon are produced in Western Oregon’s Willamette Valley, where two-thirds of the acreage is planted to Pinot noir. The production of Pinot noir in the Willamette Valley comes at a high cost, and growers are seeking ways to increase profits while maintaining quality fruit production. Not many studies have addressed the impacts of vineyard management practices on bud fruitfulness, an important component of yield. To understand the impacts of pruning method (cane and spur) and N fertilization (N fertilization and no fertilization) on Pinot noir fruitfulness and yield, two separate experiments were conducted in commercial Pinot noir vineyards in Oregon.
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. Cane- and spur-pruned vines were monitored over the course of two growing seasons and three dormant periods to determine the effect of pruning method on bud fruitfulness, vine growth, yield, and fruit composition. It was hypothesized that spur-pruning may lead to reduced yields when compared to cane-pruned vines, and that basal buds of Pinot noir would be fruitful regardless of pruning method. Results from the pruning trial indicate that basal buds of cane- and spur-pruned vines contain floral primordia, and similar primary bud fruitfulness and inflorescence primordia size were found regardless of pruning method. Vine growth was similar between treatments, and there was no effect of pruning method on yield and fruit composition. Differences in cluster architecture did exist; however, spur-pruned vines had more clusters of smaller size.
Nitrogen (N) fertilization is often avoided, as it is thought to create excess vegetative vigor and have a detrimental effect on wine quality; however, N-deficiency can lead to reduced yields. Nitrogen was applied in the amount of 44.8-67.3 kg N/ha/yr (40-60 lbs N/acre/yr) via fertigation in a low N site, and we evaluated the effect of nitrogen fertilization on bud fruitfulness, vine growth, yield, and fruit composition. It was hypothesized that N-fertilized vines would result in increased bud fruitfulness and yield. Bud fruitfulness was increased in N-fertilized vines after one year of N application, but differences did not exist within the primary bud. Bud fruitfulness was not affected after two years of N application. Early season vine growth was higher in N-fertilized vines after one year of N application, and pruning weights were higher after two years of N fertilization. We analyzed the legacy effect on N fertilization in a block that was supplied with 40-60 lbs N/acre in the two years prior to data collection. Nitrogen fertilization in this block did not affect bud fruitfulness, yield, or fruit composition, but pruning weights were increased in the N-fertilized vines. Overall, the effect of N fertilization on vegetative growth was minimal, and yield and fruit composition were similar between N-fertilized and non-fertilized vines.
Vine vigor was related to bud fruitfulness parameters in both experiments. In the N trial, greater bud fruitfulness was related to larger dormant cane size (weight and internode diameter). In both trials, greater inflorescence primordia size was observed with larger dormant cane internode diameter. The results of this work indicate that vine vigor affects Pinot noir bud fruitfulness more so than the dormant pruning and nitrogen fertilization practices used in these studies. In addition, basal buds of Pinot noir are fruitful. Thus, spur pruning is a viable option for Oregon Pinot noir producers and may decrease dormant pruning costs. Additionally, N application at the rates used herein had little impact on Pinot noir bud fruitfulness, vegetative growth, and yield.