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Harvest Operations

Harvest Operations. Tuber bulking vs vine kill timing Equipment operation Crop maturity Vine killing Bruise susceptibility. Potato Growth Stages. Physical Maturity (Skin set). Methods to measure skin set. High . Torque . Low . Low . High . Skinning damage .

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Harvest Operations

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  1. Harvest Operations • Tuber bulking vs vine kill timing • Equipment operation • Crop maturity • Vine killing • Bruise susceptibility

  2. Potato Growth Stages

  3. Physical Maturity (Skin set)

  4. Methods to measure skin set High Torque Low Low High Skinning damage

  5. Water loss from a potato in storage 98% through skin 2% through lenticels Increases water loss by 3 to 5 fold

  6. Changes in tuber composition with maturity Knowles et. al., WSU, Pullman Physiological Maturity = 145 DAP

  7. Physiological Maturity (chemical maturity) Defined as the average of date when: • Maximum yield • Maximum specific gravity • Minimum sucrose • Minimum reducing sugars

  8. Physiological Maturity DatesDays after planting * All cultivars reached maturity between 2800 and 3000 degree days

  9. Sugar Ends can Increase With Increasing Maturity of Ranger Russet Courtesy Mel Martin, J.R. Simplot Co.

  10. Crop Maturity Factors that influence crop maturity: • Variety (Determinate vs indeterminate) • Emergence date • Nitrogen fertilization • Irrigation • Disease pressure

  11. Crop Maturity Important reasons for correct maturity : • Simplify vine killing • Minimize harvest damage • Maximize tuber solids • Minimize tuber sugars • Maximize storability

  12. Vine Killing Reasons: • Regulate maturity • Prepare tubers for handling • Control tuber size • Coordinate harvest with appropriate season (need to balance equipment capabilities with climatic conditions)

  13. One main focus of harvest management is bruise reduction - Estimated to cost the US potato industry $298 million annually (1996) - Processing contract incentives - Rejections at market (5% internal defects) - Storage losses (Shrink and rot) - Losses in productivity (processing and fresh pack)

  14. Black spot bruise (a chemical reaction) occurs just beneath the vascular ring (not visible), and skin is not broken. Shatter bruise breaks the skin, and is a physical damage.

  15. Chemistry of Black Spot Bruise • Tyrosine (a substrate) and polyphenoloxidase (PPO - an enzyme) mix within a cell when cell membranes are damaged • Oxidation (addition of oxygen) occurs forming intermediate compounds • End result is melanin (black, gray, or brown color) • Process takes 12 to 72 hours, depending on temperature Brook, R.C. 1996. Potato Bruising. National Potato Anti-bruise Committee

  16. Effect of tuber susceptibility and harvester operation on bruise damage Source: Thornton et al., 1973

  17. Tuber Physical Properties Affecting Bruise • Tuber Size • Large tubers > damage small tubers • Small radius (end) > damage large radius • Cell Size • Large cells > damage than small cells • Growth conditions play large roll in cell size • Age • Blackspot increases with vine maturity • Tubers less susceptible after one month curing – tubers can withstand 30-80% more impact Brook, R.C. 1996. Potato Bruising. National Potato Anti-bruise Committee

  18. Tuber Susceptibility to Black Spot Bruise • Mineral Nutrition • N and P do not directly affect susceptibility. • Indirectly – deficiency results in earlier senescence and more mature tubers. • Indirectly – high specific gravity > blackspot than low specific gravity (N and P both affect specific gravity). Brook, R.C. 1996. Potato Bruising. National Potato Anti-bruise Committee

  19. Research on Potassium and Black Spot Bruise • Black spot bruise potential decreased with increased potassium application in excess of that needed for optimum yield. • Shatter bruise increased with more potassium. • For each 100 pounds potassium, specific gravity decreased 2.5 to 3.5 points. Porter, Greg and P.C. Ocaya. Bruise susceptibility and potassium uptake of Russet Burbank potatoes in response to varied potash rate and timing. University of Maine. Presentation at 2005 PAA meeting. Calgary.

  20. Two requirements for blackspot bruise: • Susceptibility to impact damage • Potential to darken after impact 0 = No Damage 5 = Most Damage

  21. Field Maturity as it Relates to Blackspot Bruising of Russet BurbankPotatoes Blackspot Severity Group1 Field Maturity (%)2 19933 17 33 48 59 19943 54 59 61 89 Mean 36 46 55 74 Resistant (<2.5) Mod. Susceptible (2.5 – 3.0) Susceptible (3.1 – 3.5) Very Susceptible (>3.5) 1. Abrasive peel test ratings where 0 = no blackspot and 5 = most damage. 2. Percent dead vines in fields in late August. 3. R-square values: 1993 = 0.37; 1994 = 0.21. Both significant at P = 0.01. Corsini, D., J. Stark, and M. Thornton. 1999. American J of Potato Research. P.221-226.

  22. Specific Gravity as it Relates to Blackspot Bruising of Russet BurbankPotatoes Blackspot Severity Group1 Specific Gravity2 Resistant (<2.5) Mod. Susceptible (2.5 – 3.0) Susceptible (3.1 – 3.5) Very Susceptible (>3.5) 1.074 1.077 1.081 1.083 1. Abrasive peel test ratings where 0 = no blackspot and 5 = most damage. 2. Average for all fields in the survey within a blackspot severity group, 1994. No relationship between specific gravity and bruise in 1993. Corsini, D., J. Stark, and M. Thornton. 1999. American J of Potato Research. P.221-226.

  23. Soil Moisture as it Relates to Blackspot Bruising of Russet BurbankPotatoes Blackspot Severity Group1 Soil Moisture (%)2 Resistant (<2.5) Mod. Susceptible (2.5 – 3.0) Susceptible (3.1 – 3.5) Very Susceptible (>3.5) 51 41 33 34 1. Abrasive peel test ratings where 0 = no blackspot and 5 = most damage. 2. Available soil water at time of tuber sampling; average for all fields within a severity group. Data for 1994 only. Little to no differences in percent soil moisture in 1993. Corsini, D., J. Stark, and M. Thornton. 1999. American J of Potato Research. P.221-226.

  24. Factors Increasing Black Spot Bruise Susceptibility • More mature vines Russet Burbank - 70% dead vines Ranger Russet - 20% dead vines • Higher specific gravity Russet Burbank - Above 1.080 Ranger Russet - Above 1.085 • Available soil moisture less than 60%

  25. Management Through Harvest • Tuber hydration • Drop height • Pulp temperature • Drop surface

  26. Tuber Hydration Level Effect on Black Spot and Shatter Bruise of Russet Burbank at 42ºF % Damage Hydrated (crisp) Dehydrated (limp) Tuber Hydration Smittle, D.A., et al. 1974. Harvesting Potatoes with Minimum Damage. Am. Potato J. 51: 153-164.

  27. Influence of Post-Vine-Kill Irrigation on Blackspot Bruise of Lemhi Russet Potatoes Irrigation Treatment Percent Blackspot No irrigation1 4 days before harvest 2 8 days before harvest 2 51 25 13 1. Soil moisture at 50% or less at vine kill. 2. No effect of irrigation if soil moisture kept at 65% or above after vine kill. Stark, J. C. January 1987. University of Idaho Potato School Proceedings. P 82-83.

  28. Impact of temperature and drop height on bruise incidence Hyde, G., R. Bajema and R. Thornton, 1993

  29. Impact of temperature and drop height on bruise incidence 50 oF on coated chain Steel surface

  30. Relationship Between Soil Temperature and Tuber Bruising During a 24-Hour Period 70 65 60 55 50 45 More Less % Bruise Temperature (°F) % Bruise Soil Temperature MN 4 am 8 am Noon 4 pm 8 pm MN Time of Day Smittle, D.A., et al. 1974. Harvesting Potatoes with Minimum Damage. Am. Potato J. 51: 153-164.

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