Crop Load Management Science or Belief System

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Crop Load ManagementScience or Belief System?

• Andrew G. Reynolds
• Cool Climate Oenology Viticulture Institute
• Brock University, St. Catharines, ON

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Low yield High wine quality?
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The Belief System
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Crop Load ManagementMust be About Balance
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The Balance Sweet Spot
SHADE OVERCROPPING
SHADE
BALANCE
HIGH VIGOUR SITE
LOW VIGOUR SITE
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What is Balance?

• Mean individual cane weights of 25 to 40 g
• Cane pruning weights of 0.3 lbs./ft of canopy
  (0.4 kg/m canopy)
• Crop loads (Ravaz Index crop size to vine size
  ratio) gt 5 lt 12
• Closer to the low end for Pinot noir and
  late-maturing reds and nearer to the high end for
  aromatic whites

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Berry Maturity
Low GDD Poor seasons Rain
Winter injury risk spacing
Reduce crop size
Increase vine size
Crop Size
Vine Size
Ravaz Index ca. 10
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Balanced vines High Wine Quality
Vines at Chateau Margaux in clay. Balanced at 2
t/a
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Balanced vines High Wine Quality
Vines at Chateau Couhins in gravel. Balanced at
6 t/a
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Points to Remember About Crop Management

• Crop control can be achieved by both pruning and
  cluster thinning
• Taking aim at a reasonable shoot density (e.g. 15
  shoots/m row) should minimize shade and get you
  close to the target crop load
• I suspect that most so-called crop load effects
  are often shoot density/ shade effects
• Often severe pruning can lead to low crops high
  shading and can be just as detrimental as
  overcropping (q.v. Chapman et al.)

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Shoot Density

• 15-25 shoots/m row
• High fruitfulness
• Optimum bud hardiness
• High Brix low TA and pH
• Enhanced varietal character
• Minimized vegetal aromas
• Enhanced color

• High (or very low) shoot density
• Low fruitfulness
• Low Brix high TA/pH
• Reduced varietal character, e.g. monoterpenes
• Increased vegetal flavors
• Poor color

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Points to Remember About Crop Load Management

• Responses to crop load reduction will vary
  substantially
• From site to site
• Between varieties
• Across vintages
• Depending on when crop adjustment is done
• Making general conclusions may be difficult and
  recommendations need to be tailored to each
  situation (here goes 45 minutes of ambiguity)

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Crop Load Management1. Some Varieties are
Non-Responsive(and others are very responsive)
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Pinot noir Response to Shoot Density and Crop
Level
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Pinot noir Response of yield and fruit
composition to shoot density, Okanagan Falls, BC
1989.These are non-crop related shade responses.
(A 20 shoot/m Scott Henry treatment improved
fruit composition vs 10 shoots/m)
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Pinot noir Response of yield and fruit
composition to crop level, Okanagan Falls, BC
1991The crop level response may not be as large
as expected
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Some sensory effects of crop level reduction on
BC and OR Pinot noir, 1989-92Proof is in the
glass

• Reductions
• Vegetal aroma (BC)
• Vegetal flavor (BC)
• Grassy aroma (OR)

• Increases
• Color (BC OR)
• Spicy/black pepper aroma (BC)
• Fruity flavor (BC OR)
• Berry aroma flavor (OR)
• Tree fruit aroma (OR)
• Currant flavor (BC)
• Astringency (BC OR)
• Finish (BC)

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Riesling Response to Shoot Density and Crop Level
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Riesling Impact of shoot density crop level on
growth, yield, and fruit composition, Kelowna,
BC, 1989-90
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RieslingImpact of Crop Level on Aroma
CompoundsA notable reduction in green
compounds with crop thinning
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RieslingImpact of Crop Level on Sensory
AttributesGreen fruit character is diminished by
thinning
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PCA of sensory data, Riesling shoot density X
crop level, Kelowna, BC 1989Shade ultimately
plays perhaps a greater role
Clusters/shoot Solid 2 bold 1.5 open 1
16 shoots/m
26 shoots/m
36 shoots/m
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Chardonnay Musqué
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Yield vs BrixA clear yield Brix relationship
THINNED TREATMENTS
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Muscat Aroma vs. Overall Quality Brix has little
apparent effect
NON-THINNED
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Chardonnay Musqué SensoryThinning in some cases
ineffective Time of thinning not critical
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Response of Icewines to Crop Load Manipulation
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Sensory Map of the Significantly Different
Attributes in 2003 Vidal Crop Level Icewines

• All sensory attributes associated with the
  thinned treatments
• Thin at veraison associated with several aroma
  flavour attributes

Data courtesy Amy Bowen, Brock University
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Sensory Map of the Significantly Different
Attributes in 2004 Vidal Crop Level Icewines

• Most attributes associated with the thinned
  treatments
• Except nut flavour which is loaded with the
  control
• Nut and honey are inversely correlated

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Crop Load Management2. Some Fruit Composition
Variables are Non-Responsive
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Individual Phenols, Cabernet Sauvignon
2004Catechin, quercetin non-responsive
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Individual Non-acylated Anthocyanins, Cabernet
Sauvignon 2004Most non-acylated pigments
responded to crop reduction
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Individual Acetylated Anthocyanins, Cabernet
Sauvignon 2004Some, e.g. malvidin, were not
responsive
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Crop Load Management3. Season can be Critical
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Brix, Cabernet Franc 2004-06Cluster thinning
increases in only 2 of 6 cases leaf removal
alone no effect or reduced
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Anthocyanins, Cabernet Franc 2004-06BLR
ineffective CT increased in 2 of 3 years CTBLR
not additive
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Colour Intensity, Cabernet Franc 2004-06 BLR
again ineffective thinning increased colour in 2
of 6 instances
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Total Phenols, Cabernet Sauvignon 2004-06Cluster
thinning increased phenols in 2 of 6 cases BLR
alone only once
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Sensory attributes, Cabernet Franc, as impacted
by viticultural treatment, 2004
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Sensory attributes, Cabernet Franc, as impacted
by viticultural treatment, 2005
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Crop Load Management4. Timing is Sometimes
Crucial to Quality (but often not!)
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Chardonnay Musqué FVTThinning was beneficial
early timing most effective
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Chardonnay Musqué PVTThinning was beneficial
timing apparently not critical
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Chardonnay Musqué Sensory PCAThinning was of
questionable benefit timing apparently not
critical
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Cluster thinning -- When to do it
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Cluster thinning -- When to do it
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When to Thin

• To reduce a potential overcrop situation in a
  specific year that may have resulted from
  conditions the previous year
• To maintain consistent yields and fruit
  composition in varieties with fruitful base
  shoots and/or secondary/ tertiary buds (mainly
  hybrids)
• To avoid overcropping in large-clustered
  varieties, particularly Syrah, Grenache,
  Mourvedre, Zinfandel, Bordeaux reds, etc.
• To get a crop to mature in a difficult year

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Conclusions and Final Thoughts

• Responses to crop load reduction will vary
  substantially
• From site to site
• Between varieties
• Across vintages
• Depending on when crop adjustment is done
• Making general conclusions may be difficult and
  recommendations need to be tailored to each
  situation
• Often so-called crop level effects may actually
  be due to shade either excess shoot density or
  excess shoot vigor due to overly-severe pruning

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Crop Load ManagementScience, Belief System, or
45 Minutes of Ambiguity?