S. Kaan Kurtural
Department of Viticulture & Enology,
California State University, Fresno
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.
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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.
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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.
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