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Table
1. Phosphorus efffects on yield and process quality. |
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P Rate
lb/acre
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Effect on US #1 Yield
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Effect on % Dry Matter
|
Effect on Sugar Levels
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0-50
|
Increase
|
Slight increase
|
Decrease
|
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above 50
|
No change
|
No change
|
No change
|
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0-100
|
Increases larger tuber size grades
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Table 2. Phosphorus fertilizer suggestions for potatoes.
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P Soil Test Level
|
Bray P-1
Soil Test, ppm
|
P2O5 to Apply
lbs/acre*
|
|
very low
|
0-5
|
100
|
|
low
|
6-15
|
80
|
|
medium
|
16-25
|
40
|
|
high
|
>25
|
0
|
|
*These amounts may be higher for table-stock and fry-stock markets.
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Table 3. Influence of phosphorus status on potato plant characteristics..
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Organ
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Deficiency
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Excess
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Leaves
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crinkled, cuppsed upward leaf-roll, dark green, brown margins
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none
|
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Stems
|
stunted, spindly
|
none
|
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Roots
|
decreased mass
|
none
|
|
Stolons
|
shortened
|
none
|
|
|
|
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Plant or Soil Fertility Level
|
|
Deficient
|
Adequate
|
Excess
|
|
Very small tubers
|
Optimal-sized tubers
|
Optimal-sized tubers
|
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High sugar levels
|
Low sugar levels
|
Low sugar levels
|
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Low dry matter
|
High dry matter
|
High dry matter
|
|
Few usable
|
Many usable
|
Many usable
|
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Over-mature tubers
|
Mature tubers
|
Mature tubers
|
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Disease susceptible
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Disease resistant
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Disease resistant
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