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University of Minnesota Extension

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Phosphorus and potassium

Find guidance on how to manage phosphorus and potassium on Minnesota croplands. We’ll cover nutrient sources, how and when to apply fertilizers and management strategies for increasing profits while reducing runoff. 

Managing phosphorus

Understanding phosphorus fertilizers

  • Methods for determining the amount of needed fertilizer and applying it.

  • Organic and inorganic phosphorus sources.

  • How fertilizers are manufactured and how crops respond to them.

Understanding phosphorus in Minnesota soils

  • About the element and its role
  • The phosphorus cycle
  • Forms of phosphorus
  • Phosphorus and soil

How to manage phosphorus and control losses

  • How crop type, tillage system and other factors affect how much phosphorus gets lost.

  • Strategies for controlling phosphorus loss.

Phosphorus in surface waters

  • Factors that affect phosphorus’ movement from agricultural land to surface water.

  • Management practices for areas at high risk for phosphorus loss.

Assessing risk of phosphorus loss from cropland

  • How to use the Minnesota Phosphorus Index to assess risk.

  • Guidance on interpreting results and implementing changes.


Managing potassium

Guide to potassium for Minnesota crops

  • Fertilizer application recommendations.

  • Testing soil and predicting potash needs.

  • How potassium reacts in soils, functions in plants and contributes to crop production.

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