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Crop Load Management Science or Belief System? Andrew G. Reynolds Cool Climate Oenology & Viticulture Institute Brock University, St. Catharines, ON.

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Presentation on theme: "Crop Load Management Science or Belief System? Andrew G. Reynolds Cool Climate Oenology & Viticulture Institute Brock University, St. Catharines, ON."— Presentation transcript:

1 Crop Load Management Science or Belief System? Andrew G. Reynolds Cool Climate Oenology & Viticulture Institute Brock University, St. Catharines, ON

2 Low yield = High wine quality?

3 The Belief System

4 Crop Load Management Must be About Balance

5 The Balance “Sweet Spot” SHADE OVERCROPPING BALANCE HIGH VIGOUR SITE LOW VIGOUR SITE

6 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) > 5 < 12 –Closer to the low end for Pinot noir and late- maturing reds and nearer to the high end for aromatic whites

7 Ravaz Index ca. 10 Crop Size Vine Size Reduce crop size Berry Maturity Low GDD Poor seasons Rain Winter injury risk & spacing Increase vine size

8 Balanced vines = High Wine Quality Vines at Chateau Margaux in clay. Balanced at 2 t/a

9 Balanced vines = High Wine Quality Vines at Chateau Couhins in gravel. Balanced at 6 t/a

10 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.)

11 Shoot Density 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

12 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…)

13 Crop Load Management 1. Some Varieties are Non-Responsive (…and others are very responsive)

14 Pinot noir: Response to Shoot Density and Crop Level

15 Pinot noir: Response of yield and fruit composition to shoot density, Okanagan Falls, BC These are non-crop related shade responses. (A 20 shoot/m Scott Henry treatment improved fruit composition vs 10 shoots/m) Shoot density (s/m row) Yield (t/ha) BrixTA (g/L) pHWine Anthocyanins (mg/L) Sig. F** *

16 Pinot noir: Response of yield and fruit composition to crop level, Okanagan Falls, BC 1991 The crop level response may not be as large as expected Crop levelYield (t/ha) BrixTA (g/L) pHWine Anthocyanins (mg/L) Full Half Sig. F*****ns

17 Some sensory effects of crop level reduction on BC and OR Pinot noir, Proof 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)

18 Riesling: Response to Shoot Density and Crop Level

19 FactorLeaf area on laterals Yield (t/a) BrixTA (g/L) pHcis-3- hexanol (  g/L) Linalool (  g/L) Shoot density (shoots per m row) TrendL**L***,Q**L,Q*NSL*,Q**L***L* Crop level (clusters per shoot) TrendNSL***L**NSL***L,Q***L** Riesling: Impact of shoot density & crop level on growth, yield, and fruit composition, Kelowna, BC,

20 Riesling—Impact of Crop Level on Aroma Compounds A notable reduction in “green” compounds with crop thinning

21 Riesling—Impact of Crop Level on Sensory Attributes Green fruit character is diminished by thinning

22 PCA of sensory data, Riesling shoot density X crop level, Kelowna, BC 1989 Shade ultimately plays perhaps a greater role 36 shoots/m 26 shoots/m 16 shoots/m Clusters/shoot: Solid= 2; bold= 1.5; open= 1

23 Chardonnay Musqué

24 Yield vs Brix A clear yield: Brix relationship THINNED TREATMENTS

25 Muscat Aroma vs. Overall Quality Brix has little apparent effect NON-THINNED

26 Chardonnay Musqué Sensory Thinning in some cases ineffective; Time of thinning not critical

27 Response of Icewines to Crop Load Manipulation

28 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

29 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

30 Crop Load Management 2. Some Fruit Composition Variables are Non- Responsive

31 Individual Phenols, Cabernet Sauvignon 2004 Catechin, quercetin non-responsive

32 Individual Non-acylated Anthocyanins, Cabernet Sauvignon 2004 Most non-acylated pigments responded to crop reduction

33 Individual Acetylated Anthocyanins, Cabernet Sauvignon 2004 Some, e.g. malvidin, were not responsive

34 Crop Load Management 3. Season can be Critical

35 Brix, Cabernet Franc Cluster thinning increases in only 2 of 6 cases; leaf removal alone no effect or reduced

36 Anthocyanins, Cabernet Franc BLR ineffective; CT increased in 2 of 3 years; CT+BLR not additive

37 Colour Intensity, Cabernet Franc BLR again ineffective; thinning increased colour in 2 of 6 instances

38 Total Phenols, Cabernet Sauvignon Cluster thinning increased phenols in 2 of 6 cases; BLR alone only once

39 Sensory attributes, Cabernet Franc, as impacted by viticultural treatment, 2004

40 Sensory attributes, Cabernet Franc, as impacted by viticultural treatment, 2005

41 Crop Load Management 4. Timing is Sometimes Crucial to Quality (but often not!)

42 Chardonnay Musqué FVT Thinning was beneficial; early timing most effective

43 Chardonnay Musqué PVT Thinning was beneficial; timing apparently not critical

44 Chardonnay Musqué Sensory PCA Thinning was of questionable benefit; timing apparently not critical

45 Cluster thinning -- When to do it TimingAdvantagesDisadvantages Flower cluster 1.Rapid and relatively inexpensive 2.Yields are not reduced 3.Vine size is maintained or increased 4.Fruit composition is improved 1.Can lead to large berry size and reduced skin:juice ratios 2.Can increase 2 nd crop and lateral shoot formation 3.Improved berry set can increase bunch rot Stage I1.Only slight yield reductions 2.Vine size and fruit composition are still improved 3.Reduces berry set slightly and clusters are thus less bunch rot-susceptible 1.More expensive 2.Less effective– the canopy is fully-formed and clusters are harder to find

46 Cluster thinning -- When to do it TimingAdvantagesDisadvantages Pre- veraison 1. Yields are reduced and skin:juice ratio is increased 2. Fruit composition is improved Expensive—labor + loss of crop Post- veraison to harvest 1. As with pre-veraison, but results are more extreme 2. Could thin off a brandy and a bubbly crop first As with pre-veraison No thinning 1.Saves money 2.Higher yields 3.The right thing to do in some years, sites, varieties 1.Possible long term reductions in yield and vine size (maybe) 2.Compromised fruit composition (maybe)

47 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

48 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

49 Crop Load Management: Science, Belief System, or 45 Minutes of Ambiguity?


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