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June 2016 WINES&VINES 51 PRACTICAL WINERY & VINEYARD GRAPEGROWING to investigate varying intensities of basal leaf removal on Pinot Noir grape quality with a focus on volatile compounds and their precursors. Materials and methods Vineyard experimental design A leaf-removal trial was conducted from 2010 to 2012 in two vineyards located in Oregon's Willamette Valley. In 2010, the trial was con- ducted at a commercial vineyard in Dayton, Ore. The vineyard was planted in 1995 to a vine density of 2,489 vines per acre with Pinot Noir clone 115 grafted to 3309C rootstock. The vine rows are oriented north-south with tractor row by vine spacing of 1 meter by 1.5 meters. In 2011 and 2012, the trial was conducted at Oregon State University's Woodhall Re- search Vineyard in Alpine, Ore. This vineyard was planted in 2006 to a vine density of 1,383 vines per acre with Pinot Noir clone Pommard grafted to 101-14 rootstock. The vine rows are oriented north-south with tractor row by vine spacing of 1.4 meters by 2.1 meters. Both vineyards were cane-pruned to a bi- lateral Guyot system and vertically shoot-po- sitioned. Standard vineyard-management practices including pest and canopy manage- ment were performed each year with the ex- ception of leaf removal. Basal leaves were removed from vines with four different intensities. Treatments included: 1) 0% leaf removal; 2) 50% leaf removal, where every other leaf along the shoot was removed starting at the basal node and work- ing up to the node above the top-most cluster; 3) industry standard (IS) leaf removal, where only leaves that covered the clusters on the eastern (morning sun) side of the vine canopy were removed, and 4) 100% of leaves removed from both the east and west side of the cluster zone, starting from the base of the shoot up to the node above the top-most cluster. The IS treatment was evaluated in 2011 and 2012 to compare treatments with com- mercial practices in vineyards. Leaf removal was imposed at one point in the growing process, the pea-sized stage of berry develop- ment, on six-vine plots in a randomized com- plete block design with five field replicates. At the time of leaf removal in the 100%, 50% and IS treatments, all lateral shoots in the cluster zone were removed. Weather data Weather data were collected onsite for each growing season. Data for daily temperature were logged and used to calculate growing degree-days and the mean daily temperature. Growing degree-day (GDD 50 ) units were cal- culated using the daily mean of T max and T min with a minimum threshold of 50° F and no maximum threshold applied. Daily precipita- tion was recorded for each growing season. Vine growth and cluster exposure Canopy size and density, photosynthetically ac- tive radiation, yield and dormant pruning weights were measured annually. In 2010, the amount of leaves removed were determined by collecting all primary and lateral leaves removed during treatment application, bringing them to the lab and scanning them on a leaf-area meter. In 2011 and 2012, more detailed leaf-area quantification was conducted. Leaf areas were measured after treatment application and at véraison. After applying leaf-removal treat- ments, both total leaf area removed and re- maining on the vine were measured using a non-destructive quantification method de- scribed in Schreiner et al. 48 The percentage of leaf area removed was calculated and com- pared between leaf removal treatments. Vine leaf area was quantified at véraison each year (2010, 2011, 2012) using the non- destructive template method described above. The template was used to measure all leaves on one randomly selected shoot from each of the six experimental vines per plot. The shoot leaf area was multiplied by shoot count to calculate whole vine leaf area. Incident light in the cluster zone was quan- tified shortly after véraison, in the early ripen- ing stages, each year on a clear, cloudless day by using a LP-80 ceptometer. This device measures photosynthetically active radiation (PAR), and it was quantified at 10 a.m., solar noon and 2:30 p.m. by placing the sensor rod parallel to the vine row at the height of the cluster zone on the east and west side of north-south-oriented vine rows. Three mea- sures were taken with the ceptometer along the plot length on each side of the canopy. Leaf area index (LAI), a measure of canopy density, was quantified using the ceptometer. At véraison, the ceptometer was placed above the cluster zone and parallel with the vine row to measure the density of the canopy above the clusters. A total of three measures were taken along the length of each six-vine plot. At harvest, whole-vine yield was quanti- fied on three randomly selected vines per plot. In the dormant period that followed each growing season, one-year-old dormant canes were pruned off and weighed. The pruning weight and yield data were used to calculate vine balance (yield per vine divided by prun- ing weight per vine). Determination of grape chemical composition Analysis of grape maturity parameters at harvest A seven-cluster sample was randomly selected from grapes harvested from each plot, trans- ported to the lab and kept cool (42.8° F) until analysis. All clusters were measured for cluster size metrics (cluster weight, berry weight and berries per cluster). The berries from the seven- cluster sample were pressed to juice to measure total soluble solids (TSS), pH and titratable acidity by titration. 63 A subset of harvested clusters were trans- ported to the lab and immediately frozen at -176° BASIC FRUIT MATURITY AT HARVEST RELATIVE TO LEAF REMOVAL Year Treatment TSS (Brix) pH TA a (g/L) 2010 (Dayton, Ore.) None 20.9° 3.14 a 10.1 50% 20.4° 3.08 b 10.0 100% 20.3° 3.09 ab 10.2 p n.s. 0.0362 n.s. None 19.8° 3.05 9.9 50% 19.9° 3.06 9.6 100% 19.4° 3.00 10.1 p n.s. n.s. n.s. 2012 (Alpine, Ore.) IS 25.0° 3.21 8.0 None 25.3° 3.27 7.8 50% 25.1° 3.24 7.7 100% 25.1° 3.19 7.7 p n.s. n.s. n.s. Means are presented (n=5); different letters indicate a difference in means between treatments using Tukey HSD mean separation at α=0.05.; n.s.: indicates no statistical differences. a: TA refers to titratable acidity shown in g/L of tartaric acid equivalents. Leaf removal treatments include the following: None (no leaf re- moval), 100% (all leaves in the cluster zone removed), 50% (half of the leaves in the cluster zone removed) and IS (industry standard where leaves are only removed in the cluster zone on the east side of the canopy).