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Crop Load Management Science or Belief System?

Crop Load Management Science or Belief System?. Andrew G. Reynolds Cool Climate Oenology & Viticulture Institute Brock University, St. Catharines, ON. Low yield = High wine quality?. The Belief System. Crop Load Management Must be About Balance. The Balance “Sweet Spot”. SHADE

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Crop Load Management Science or Belief System?

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  1. Crop Load ManagementScience 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 ManagementMust be About Balance

  5. The Balance “Sweet Spot” SHADE OVERCROPPING SHADE 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. 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

  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. 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 Shoot Density

  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 Management1. 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 1989.These are non-crop related shade responses. (A 20 shoot/m Scott Henry treatment improved fruit composition vs 10 shoots/m)

  16. 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

  17. 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) Some sensory effects of crop level reduction on BC and OR Pinot noir, 1989-92Proof is in the glass

  18. Riesling: Response to Shoot Density and Crop Level

  19. Riesling: Impact of shoot density & crop level on growth, yield, and fruit composition, Kelowna, BC, 1989-90

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

  21. Riesling—Impact of Crop Level on Sensory AttributesGreen fruit character is diminished by thinning

  22. 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

  23. Chardonnay Musqué

  24. Yield vs BrixA clear yield: Brix relationship THINNED TREATMENTS

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

  26. Chardonnay Musqué SensoryThinning 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 Management2. Some Fruit Composition Variables are Non-Responsive

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

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

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

  34. Crop Load Management3. Season can be Critical

  35. Brix, Cabernet Franc 2004-06Cluster thinning increases in only 2 of 6 cases; leaf removal alone no effect or reduced

  36. Anthocyanins, Cabernet Franc 2004-06BLR ineffective; CT increased in 2 of 3 years; CT+BLR not additive

  37. Colour Intensity, Cabernet Franc 2004-06BLR again ineffective; thinning increased colour in 2 of 6 instances

  38. Total Phenols, Cabernet Sauvignon 2004-06Cluster 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 Management4. Timing is Sometimes Crucial to Quality (but often not!)

  42. Chardonnay Musqué FVTThinning was beneficial; early timing most effective

  43. Chardonnay Musqué PVTThinning was beneficial; timing apparently not critical

  44. Chardonnay Musqué Sensory PCAThinning was of questionable benefit; timing apparently not critical

  45. Cluster thinning -- When to do it

  46. Cluster thinning -- When to do it

  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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