Wines & Vines

GRAPEGROWING produced 80% and 36% less crop weight, respectively, than vines with tilled tractor rows (high vigor). Results from this study suggest that the vine physiologically strives to obtain balance between vegetative and reproductive growth, and in years with reduced fruit set, more lateral shoot growth and crop development will occur to obtain more balanced growth. During 2010, another low fruit set year, similar effects in lateral crop development were observed but not quantified lateral crop weight than vines thinned by 35% or not thinned at all. Although this difference was clear, the effect of vine vigor and nitrogen status from the vineyard floor management study was more pronounced in altering lateral shoot growth and lateral crop production than crop level. Both the timing of cluster thinning and N-status of the vine likely influence the presence and growth of lateral shoots, thereby affecting the amount of lateral crop produced. Although there 400 23.0 22.7 20.0 ab 300 ab 250 b 200 15.0 10.0 0.0 50 0 Pre-bloom Fruit set Lag phase Véraison Figure 1. Total weight (mean ± SE) of lateral crop removed at véraison from vines in a cluster-thinning trial. Primary clusters were thinned at four different time intervals in 2012. Different letters indicate differences in means at P=0.0283, Tukey's HSD mean separation. in commercial vineyards and within this particular trial, but these observations spurred further study in years of low fruit set. In 2011, Oregon had record high fruit set and yield. As a result, little to no lateral crop development was observed and quantified within our Pinot Noir trials. However, within a three-year crop load trial (2010-12), timing and intensity of cluster thinning influenced development of lateral crop. In this particular study, two levels of cluster thinning (65% and 35% reduction in yield) at four time points (pre-bloom, fruit set, lag phase and véraison) were compared to full-crop vines. Vines that were cluster-thinned prebloom produced more total lateral crop than vines thinned later (Figure 1). The intensity of cluster thinning also influenced lateral crop development. Those vines thinned to the lowest level (65% lower yield) had 17%–22% more 10/24/12 100 10/18/12 5.0 10/2/12 150 10/10/12 weight /vine (g) 25.0 a TSS (ºBrix) 350 test this theory, an experiment was conducted in 2012 where lateral crop was removed or retained on vines at véraison to determine the impact on ripening primary clusters. The lateral crop clusters were weighed upon removal. Vines of moderate vigor averaged 22.5 g (± 21.2 g) per vine while vines of higher vigor averaged 151.3 g (± 23.5 g). At that time, lateral crop was in the first or second stage of berry development as berries were green, hard and fairly small. Figure 2. Lateral cluster maturity progression during late season 2012. Single markers (top left) indicate the TSS of the primary clusters harvested on that date (23.0 = primary clusters with lateral crop maintained on vines; 22.7 = primary clusters without lateral crop). were no statistical differences found in lateral number, length and total lateral shoot leaf area between different timing and level of cluster thinning compared to full crop, differences may have existed but could not be measured given the repeated hedging that occurs per normal production practices. Hedging influences our ability to adequately quantify lateral shoot growth, length and leaf area, but it has less impact on the lateral crop weight measured. Based on these studies, it is apparent that the vine strives for balance between vegetative and reproductive growth. However, this is a concern when it comes to ripening the primary crop, particularly in the cool-climate production regions of Oregon, where fall is characterized by cool days and nights and increasing risk of rain. Many growers will remove lateral crop in hopes that it will not compete with the primary crop during ripening. To Full bloom of lateral crop began in late July, and development of new blooming clusters occurred over the remaining growing season. This suggests that the vines were in a stage of continuous reproductive development through much of the season, with potential competition of primary clusters with the canopy and lateral crop. With higher vigor, vines had a greater proportion of lateral crop fruit than moderate-vigor vines, similar to other data collected in trials from 2010 and 2012. The primary and lateral crop clusters from each experimental vine were harvested separately Oct. 2, 2012. While the primary fruit was considered ripe by commercial standards, lateral crop clusters were at approximately the 50% véraison stage. Despite the presence of lateral crop on vines in this experiment, there were no differences in the primary cluster maturity (total soluble solids, pH and TA) from vines without lateral crop pr actica l win ery & vin eya r d AU GU ST 20 13 83

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