Potato Plant Nutrition For Growers
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Phosphorus

Phosphorus Accumulation in Units/Acre in Relation to Yield

Tons/Ac 15 dae 30 dae 45 dae 60 dae 75 dae 90 dae 105 dae 120 dae
25 26 143 427 489 540 529 510 499
30 31 172 513 587 648 635 612 599
35 37 200 598 684 756 740 714 699
40 42 229 683 782 864 846 816 799

85% of the total K content of vine is translocated to the tubers. At 45 dae to 90 dae, 75% of the K is translocated to the tuber. After 75 dae, ½ of the K should be already in the tuber.

The NPK ratio of the whole plant is about 8:1:9, in short K is as important as nitrogen. Problem: Petiole testing for K is not an accurate indicator of K availability. K is very mobile in plants, therefore a petiole test indicates that K is low at the end of a 2′ to 3′ vine.

Daily potassium uptake rates are crucial to incorporate into a potassium fertilization program. Do you know your soils daily K release rate? Did you know that for 25-30 tons/acre, the release rate needed could be has high as 15-20 units/day? Please view the potassium uptake and utilization video for important information.

Phosphorus Facts

  • Low spring soil temperature suppresses P uptake
  • Although calcareous soils tie up P, increased Ca in solution increases P uptake because calcium stimulates transport of P into the cell. (NUE 8-22-0 mixes with Cal-8 and CN9) Total ratio P:Ca is about 0.9:1
  • Magnesium also stimulates the reactions in a plant involving P transfer. Total ratio of P:Mg is about 1.1:1
  • High petiole iron can mean suppressed P availability and translocation
  • High P can suppress Zn. The total level of P is reached at 45 dae, whereas Zn is at 45% of total uptake at 45 dae. Optimum ratio of P:Zn is 142:1
  • Low P levels reduce translocation of starch from leaves

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