Practical Winery
65 Mitchell Blvd, San Rafael, CA 94903
phone: 415-453-9700 ext 102
email: Office@practicalwinery.com
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Spring 2011
GRAPEGROWING
BY
S. Kaan Kurtural
Department of Viticulture & Enology,
California State University, Fresno
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rowers in the San Joaquin Valley (SJV) rely on large yields to be profitable. Despite their abundant volume (70% of winegrapes crushed), these winegrapes receive only about 25% of the winegrape farm receipts in California.
Producing high yields may be necessary, but achieving the optimum level of production can be an elusive goal for these growers. If yields are too low, the vineyard will not be financially sustainable.
However, if growers retain too many buds at pruning, the vines will become overcropped and out of balance resulting in an undesirable canopy microclimate, leading to lower fruitfulness and fruit quality in the following year.
Adopting more mechanization is one way growers can lower farming costs. Canopy management practices traditionally done manually, such as dormant pruning, shoot thinning, shoot positioning, cluster thinning,8 leaf removal,7,30 and hedging, have significant effects on vine growth3,8,10,20,25, 26,29,1,2,5,6,21,24 and fruit quality12,15,17,19, 23,26,28 and can be done mechanically with potential cost savings.
Research is needed to test mechanization technologies and determine their short- and long-term effects on vine production and health.10,18,21
To help growers in the San Joaquin Valley, a four-year trial (2010 through 2013) was established to determine the effects of mechanical canopy management (dormant pruning, shoot thinning, and leaf removal) on vine production. The study will monitor canopy microclimate, cluster architecture, yield components, and ripening in Pinot Grigio and Syrah vineyards.
Results from this study will expand knowledge about growing Pinot Grigio and Syrah, provide information for growers on mechanical canopy management methods, and identify any potential problems for vine health associated with the new mechanized canopy management practices.
Trial vineyards, treatments, and measurements
The trial is being conducted with Pinot Grigio (clone 03 on 1103P) and Syrah (clone 06 on SO4) in vineyards planted in 2003 and 1999, respectively. Both vineyards (Arvin, CA) are spaced 7 x 11 feet (vine x row), trained to bilateral cordon in rows oriented northsouth. The vineyards have been under mechanical management since Spring 2008, and the vines now produce consistent yields.
TOP LEFT: In Arvin, CA., an Oxbo Model 62084 leaf removal implement with a rotary blade gently vacuums the outer layer of Syrah leaves on the morning side (20 days post-bloom), into a drum where a rotary cutter shreds and discharges spent leaves onto vineyard floor.
TOP RIGHT: Oxbo implement removed an 18-inch tall leaf layer from the fruit zone of Syrah canopy on the morning side. Recently formed clusters, prior to flowering, are visible in the canopy.
ABOVE: Syrah clusters at 80% veraison, where an 18-inch tall window of leaves was removed from morning side of the vines.
Replicated treatments were imposed to sustain yields of 8 to 9 tons per acre for Syrah and 8 to 10 tons per acre for Pinot Grigio. The vineyards are irrigated weekly by a drip system at 80% of evapotranspiration when mid-day leaf water potential is below -1.2 MPa (12 bars).
All other cultural practices are standard for the San Joaquin Valley and conducted according to University of California Cooperative Extension guidelines.
In each vineyard, the trial is testing the effects of mechanically performed canopy management treatments consisting of two dormant pruning levels, three shoot density levels, and two leaf removal levels in four randomized complete blocks.