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Cooperative Extension: Cranberries

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How to Grow Cranberries - Common Cranberry Plant Nutrition Questions

by Teryl R. Roper.  © 2008. (during his time at the Dept. of Horticulture, Univ. of Wisconsin-Madison)


[See also the following pdf: Nitrogen for Bearing Cranberries in North America]

Cultivar Optimum growth before early bloom
Early Black 50-60 mm   (2-2.5 in)
Howes 45-55 mm   (1.75-2 in)
Ben Lear 55-65 mm   (2-2.5 in)
Stevens 60-70 mm   (2.5-2.75 in)


[See also the following pdf: Phosphorus for Bearing Cranberries in North America]


  • What is the role of K in plant growth? Potassium does not have a direct role in plant metabolism.  It is not involved in proteins or membranes.  It is primarily used to balance charges and as an osmoticant (used to move water from place to place).  K is also important to stomata opening and closing and in the movement of sugars from one place to another.
  • What is the optimum timing for K application? Since K+ will leach, it is important to have frequent light applications of K as opposed to 2-3 large applications at ‘critical’ times.  In Wisconsin research, different timings for K fertilizer did not affect yield or rot.
  • Do I need more K on sand than peat beds? Research does not show differences in K response on sand or peat-based soils.
  • How much K is required annually? Research showed yield differences related to K rate in only 1 of 4 years.  There was no relationship between K rate and tissue K.  Interestingly, yield was reduced at high K rates (240 lbs K2O/a)[215 kg/ha].  60-100 lbs K2O/a/yr [55-90 Kg/ha] appears sufficient.  High K was correlated with decreased Ca, Mg, & Fe. Apparently, high K applications exchanged other cations off the exchange sites in the soil. I would determine that through tissue testing in the late summer.
  • Are there cultivar differences in K requirement? Not that I am aware of.
  • Can I minimize K leaching on sandy soils? The only approach I know of is to be cautious with other cation nutrients (Ca, Mg, Fe) and then over time an organic duff layer will form.  This layer will have more exchange sites and will hold onto K (& other cations) better than sand alone.
  • What forms of K are available? See the question below that asks: What is the difference between 0-0-50 and 0-0-60?
  • Is one better than another on sandy soils or new plantings? In all cases potassium sulfate is preferred over potassium chloride.
  • Can I optimize K uptake in soils with high Ca & Mg? Frequent light applications of K would allow it to be more available than 1-2 heavy applications.  K will compete with Ca & Mg for exchange sites.  Overapplication of Ca & Mg will reduce K availability.  However, see also the answer up above for the question: How much K is required annually?
  • Foliar applications of K during bloom & early fruit set? Research shows no effect of timing on yield.  Research also shows no effect of different products when applied at the same rate of K.
  • What is the difference between 0-0-50 and 0-0-60? 0-0-50 is potassium sulfate (KSO4) and 0-0-60 is potassium chloride (muriate of potash, KCl).  Cranberries are sensitive to chloride, so the sulfate form is generally preferred.  However, research in Wisconsin has shown that at normal application rates (<400 lbs/a) both the chloride and sulfate forms provided equal results and no plant injury was observed.
  • Will high application rates of potassium result in larger or better colored fruit? Research shows that yield, fruit number, fruit size, and fruit color do not vary by rate of K application.
Fertilizer Chemical formula Analysis Solubility
Triple superphosphate Ca(H2PO4)2 0-46-0 87%
Diammonium phosphate (NH4)2 HPO4 18-46-0 100%
Monoammonium phospate NH4H2PO4 11-48-0 100%
Ammonium polyphosphate (dry) NH4H2PO4+(NH4)3HP2O7 10-34-0 100%
Ammonium polyphosphate (liquid) NH4H2PO4+(NH4)3HP2O7 15-62-0 100%
Ordinary superphosphate Ca(H2PO4)3+CaSO4 0-20-0 85%
Phosphoric acid HPO4
Rock phosphate low



pH Management:

Initial pH Sand or Loamy Sand Sandy Loam or Loam
lb./acre lb./acre
7.0 800 2500
6.5 650 2000
6.0 525 1500
5.5 350 1000
5.0 170 500


Cranberry questions? Contact Charles Armstrong, Cranberry Professional. University of Maine Cooperative Extension || Pest Management Office || 491 College Avenue || Orono, ME 04473-1295 || Tel: 207.581.2967 [email:]

Image Description: A closeup of a single Maine cranberry, with an oval frame effect around it, just to help decorate the page

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Contact Information

Cooperative Extension: Cranberries
5741 Libby Hall
Orono, Maine 04469-5741
Phone: 207.581.3188, 1.800.287.0274 (in Maine) or 1.800.287.8957 (TDD)E-mail:
The University of Maine
Orono, Maine 04469