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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
Harvest Operations

  • Tuber bulking vs vine kill timing

  • Equipment operation

  • Crop maturity

  • Vine killing

  • Bruise susceptibility




Methods to measure skin set
Methods to measure skin set

High

Torque

Low

Low

High

Skinning damage


Water loss from a potato in storage
Water loss from a potato in storage

98% through skin

2% through lenticels

Increases water loss by 3 to 5 fold


Changes in tuber composition with maturity

Knowles et. al., WSU, Pullman

Physiological Maturity = 145 DAP


Physiological maturity chemical maturity
Physiological Maturity (chemical maturity)

Defined as the average of date when:

  • Maximum yield

  • Maximum specific gravity

  • Minimum sucrose

  • Minimum reducing sugars


Physiological maturity dates days after planting
Physiological Maturity DatesDays after planting

* All cultivars reached maturity between 2800 and 3000 degree days


Sugar Ends can Increase With Increasing Maturity of Ranger Russet

Courtesy Mel Martin, J.R. Simplot Co.


Crop maturity
Crop Maturity Russet

Factors that influence crop maturity:

  • Variety (Determinate vs indeterminate)

  • Emergence date

  • Nitrogen fertilization

  • Irrigation

  • Disease pressure


Crop maturity1
Crop RussetMaturity

Important reasons for correct maturity :

  • Simplify vine killing

  • Minimize harvest damage

  • Maximize tuber solids

  • Minimize tuber sugars

  • Maximize storability


Vine killing
Vine Killing Russet

Reasons:

  • Regulate maturity

  • Prepare tubers for handling

  • Control tuber size

  • Coordinate harvest with appropriate season (need to balance equipment capabilities with climatic conditions)


One main focus of harvest management is bruise reduction Russet

- 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)


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.


Chemistry of Black Spot Bruise the vascular ring (not visible), and skin is not broken.

  • 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


Effect of tuber susceptibility and harvester operation on bruise damage

Source: Thornton et al., 1973


Tuber Physical Properties Affecting Bruise bruise damage

  • 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


Tuber Susceptibility to Black Spot Bruise bruise damage

  • 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


Research on Potassium and bruise damageBlack 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.


Two requirements for bruise damageblackspot bruise:

  • Susceptibility to impact damage

  • Potential to darken after impact

0 = No Damage

5 = Most Damage


Field Maturity as it Relates to bruise damageBlackspot 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.


Specific Gravity as it Relates to bruise damageBlackspot 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.


Soil Moisture as it Relates to bruise damageBlackspot 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.


Factors Increasing bruise damageBlack 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%


Management Through Harvest bruise damage

  • Tuber hydration

  • Drop height

  • Pulp temperature

  • Drop surface


Tuber bruise damageHydration 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.


Influence of Post-Vine-Kill Irrigation on bruise damageBlackspot 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.


Impact of temperature and drop height on bruise incidence
Impact of temperature and drop height on bruise incidence bruise damage

Hyde, G., R. Bajema and R. Thornton, 1993


Impact of temperature and drop height on bruise incidence1
Impact of temperature and drop height on bruise incidence bruise damage

50 oF on coated chain

Steel surface


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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