Vineyard Floor Management Influences ‘Pinot noir’ Vine Growth and Productivity More than Cluster Thinning

Abstract

<jats:p>Vigor and crop level management are important practices for premium wine grape production. The implications of crop thinning ‘Pinot noir’(<jats:italic>Vitis vinifera</jats:italic> L.) vines of varying vigor were investigated in the Willamette Valley of Oregon in 2011 to 2013 to better understand the relationship between canopy size and yield within the framework of a cool-climate, premium production wine grape vineyard. To manipulate vigor, a competitive grass cover crop (<jats:italic>Festuca rubra</jats:italic> L.) was grown in both (Grass), alternating (Alternate), or neither side of the flanking alleyways (Tilled). Vines within each vineyard floor treatment had two crop levels applied, including cluster thinning to one cluster per shoot (Half Crop) or no crop thinning (Full Crop). Grass treatment had reduced leaf area and leaf nitrogen (N) concentrations during all years compared with Tilled treatments. Leaf photosynthesis was also lower in Grass treatments despite more light in the canopy interior. Grass treatments had lower yield than Tilled treatments in 2 of 3 years and lower yeast assimilable nitrogen (YAN) concentrations in fruit every year. There was limited impact of floor treatments on total soluble solids (TSS) and pH. Reduced yields through cluster thinning had limited impact on vegetative growth but increased TSS and pH, in 2 of 3 years. There were few floor management by crop level interactions in any year. Grass effectively reduced vegetative growth to moderate vigor levels with cane weights between 20 and 40 g. Using a competitive grass cover crop may be an effective strategy to reduce excessive vine growth and require less labor in canopy management and crop thinning without compromising basic fruit ripeness, although YAN levels need to be monitored.</jats:p>

Nitrogen Requirements of Pinot noir Based on Growth Parameters, Must Composition, and Fermentation Behavior

“…These differences were not as large as those reported previously, but vines here were grown under field conditions, where solar heating may also have influenced bud temperature (May 2004). Since N supply had no influence on flower number per inflorescence over a three year period, our data do not support recent findings that N status in the previous growing season influences flower number in the subsequent year (Guilpart et al 2014), nor do they support findings from a vineyard floor trial where lower flower number was related to lower N status of vines (Reeve et al 2016). Differences among these studies and our findings may be due to other factors, including vine age and weather conditions, that may interact with N status in influencing flower numbers per inflorescence.…”

“…Our data suggest that viticulturists in the region have some room to adjust vine N status to reduce canopy size and possibly improve fruit composition before suffering a yield loss. Reduced N status could be achieved by reducing N inputs directly, or by other means such as increasing competitive vineyard floor vegetation or using low N rootstocks (Reeve et al 2016). The caveat is that must YAN levels appear to be slightly more sensitive to low N status, so lower YAN levels will accompany lower vegetative growth.…”

“…These goals are important components of vineyard sustainability programs that vineyards and wineries can utilize to gain market share for their products (Schäufele and Hamm 2017). N management will be more challenging to fine-tune in non-irrigated vineyards, but some practices, including the use of competitive cover crops, can also reduce vine N status and canopy size with less impact on yield (Reeve et al 2016). Ongoing research is addressing whether or not N fertilization in low-N vineyards to boost native fruit YAN produces better wines, or whether maintaining low vine N status, with or without winery YAN additions, produces better wines.…”

Agronomical and Chemical Effects of the Timing of Cluster Thinning on Pinot Noir (Clone 115) Grapes and Wines

“…The GDD variation observed at this site between 2016 and 2017 corresponds to approximately 1.5 • C higher average temperatures in 2017. It is well documented that vine capacity and the ability to achieve ripeness by Brix accumulation in cool regions is dependent upon climatic conditions such as temperature [48,52,53], with a base level of temperature required to adequately ripen fruit. However, Brix accumulation is not driven solely by temperature and, by extension, by GDD accumulation.…”

“…Overall, there was no consistent effect of cluster thinning on fruit TA across both growing seasons (Table 3). Previous studies on Pinot noir, in which half of the crop was thinned, have found increased pH [19,53] in both fruit and juice, but mixed effects on TA, showing either no impact [19] or a reduction in TA with cluster thinning [53]. While no significant treatment effect of pH was found in the present study after considering the growing season, the inconsistent results observed in bloom + 12 fruit is similar to what has been found in previous research, suggesting the influence of some external factor on malate degradation in late-thinned fruit.…”