Potato Plant Nutrition For Growers
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Potassium

Potassium 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.

Potassium Facts

  • K is involved is required for the accumulation (starch in tubers) and translocation (sugar to tubers) of sugars from photosynthesis
  • Growth is slowed when sugars accumulate in the vines (hot days = good photosynthesis + warm nights = poor translocation = poor solids)
  • High N increases disease pressure, High K decreases disease pressure
  • K & N fertilization must be balanced; high K suppresses N in young plants and high N with low K results in increased “stem” growth & poor tuber development
  • Generally, high nitrate increases K uptake, whereas high ammonia suppresses K. Sufficient Ca nullifies the negative effect of ammonia on K
  • High K has a greater suppressing effect on Mg or Ca then either of these two has on K
  • High K suppresses the uptake of Calcium, ratio of K:Ca is 8.2:1
  • Soil uptake of K is more suppressed by low soil oxygen contents (over watering) than any other nutrient. Good water management = Good K uptake
  • At bloom stage, many plants can “luxury feed” K
  • Two important timings for K; Bloom (row closure) and bulking (60 dae to 80 dae)

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