What is Potassium?

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Potassium is an essential plant nutrient used in key intracellular processes for supporting plant growth, including sugar and nutrient transport, stomatal regulation, photosynthesis, and acting as a catalyst for plant enzymatic processes.  Availability to plants is heavily controlled by the form in which potassium is found in the soil, which may include forms such as exchangeable potassium, soil solution potassium, fixed potassium, and unavailable potassium.

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Regional Educator ResourcesOther Educator ResourcesTechnical Resources
Title Source Resource type and Date Short Summary / Preview
Potassium for crop production University of Minnesota Extension Webpage


Potassium (K) is an essential nutrient for plant growth. It’s classified as a macronutrient because plants take up large quantities of K during their life cycle.
Phosphorus and Potassium Fertilization of Alfalfa Purdue University Extension Publication

Mar 2009

Publication explores potassium fertilization for alfalfa.
Potassium (Chapter 12 of Soil Fertility: A Guide to Organic and Inorganic Soil Amendments) Northeast Organic Farming Association Online  Book Chapter

Mar 2013

This is a chapter that describes and discusses the role of potassium in crop development and in the soil. Tables are provided that identify sources of potassium for organic and inorganic farming operations.  It discusses how different sources work and expected results from these.
Soil Potassium Availability: The Roles of Manure, Irrigation and Potassium Feldspar University of Nebraska Extension Article

Dec 2019

Exchangeable potassium (K) becomes a critical consideration when soil test levels drop below 125 ppm. Dr. Charles Wortmann, Nebraska Extension Nutrient Specialist, recommends regular potassium testing (0-8” depth) to maintain greater than 125 ppm soil levels.
Tri-State Fertilizer Recommendations for Corn, Soybeans, Wheat and Alfalfa Michigan State University, The Ohio State University, Purdue University Extension Publication

Jul 1995

In this publication, we have developed common fertilizer recommendations for the major crops in Michigan, Ohio and Indiana.
Potassium: The overlooked nutrient in crop production Michigan State University Extension Article

Mar 2017

Understanding potassium’s role as an essential plant and animal nutrient is critical to alleviating some emerging crop production and human health issues. This article provides information on the role of potassium in plant development as well as its importance in human nutrition. Crops that require high amounts of potassium (K) are discussed and possible sources are provided.
Wheat Production and Fertilization in Indiana Purdue University Extension Publication

Nov 1992

Publication reviews fertilizer recommendations (including potassium) for Indiana wheat production.
Crop Specific K Recommendations Purdue University University Webpage

Not Dated

List of publications and resources for many crops as it relates to their need for Potassium.
Tri-State Fertilizer Recommendations for Corn, Soybeans, Wheat and Alfalfa Purdue University Extension Publication

Jul 1995

In this publication, we have developed common fertilizer recommendations for the major crops in the tri-state region.
Other Nutrients SARE Book Excerpt


Although farmers understandably focus on nitrogen and phosphorus—because of the large quantities used and the potential for environmental problems—additional nutrient and soil chemical issues remain important.
Developing Phosphorus and Potassium Recommendations for Field Crops The Ohio State University Extension Fact Sheet

Nov 2012

This fact sheet describes how to use a soil test result and tables in Tri-State Fertilizer Recommendations for Corn, Soybeans, Wheat & Alfalfa to develop phosphorus and potassium nutrient recommendations. The nutrient recommendations are then developed into a fertilizer recommendation.
Excel Spreadsheet to Calculate P, K and Lime Recommendations (Version 2014-1) The Ohio State University Excel Spreadsheet

May 2014

Spreadsheet for use in calculating phosphorus, potassium, and lime amounts for crop production.
Title Source Resource type and date Short Summary
Nitrogen-Phosphorus-Potassium Values of Organic Fertilizers Oregon State University University Publication

Jun 2003

This is a list of sources of nitrogen, potassium, and phosphorous that can be used in any production system including organic production systems. A table is provided that indicates the rate of nutrient release for the crops, listed by each suggested source.
Potassium recommendations for field crops in New York Cornell University University Publication

Jun 2003

This document is specific to field crops in New York. Five soil classes are described which are common to other states in the Midwest.  Potassium availability is described based on each soil class. Examples are provided to demonstrate how the amount of K needed is calculated depending on the soil class and crop in question.
Soil Nutrient Management For Forages: Phosphorus, Potassium, Sulphur, and Micronutrients Montana State University Extension Publication


Improvements in forage production have the potential to increase income and significantly reduce livestock production costs. Soil fertility is important for forage production, stand health/longevity, and forage quality.
Potassium for Crop Production Penn State University Extension Webpage

Sep 2015

Ways to insure optimum potassium fertilization on your farm.
Fact Sheets Potassium Soilquality.org – Australia University Webpage (Australia)

Not Dated

Potassium (K) is one of the essential nutrients in plants and in recent years is one of three (including nitrogen and phosphorus) that are commonly in sufficiently short supply in the soil to limit crop yields on many soil types in Western Australia.
Managing Potassium for Organic Crop Production International Plant Nutrition Institute Peer-Reviewed Publication


An adequate K supply is essential for both organic and conventional crop production. Potassium is involved in many plant physiological reactions, including osmoregulation, protein synthesis, enzyme activation, and photosynthate translocation. An overview of commonly used K fertilizers for organic production is provided.
Managing Potassium for Crop Production Penn State University Extension Publication

Sep 2017

This publication explores potassium use and removal by corn.
Potassium Guidelines for Corn Cornell University Extension Fact Sheet

Jun 2014

This fact sheet discusses potassium management for corn production.
Soil Fertility Management for Forage Crops: Maintenance Penn State University Extension Fact Sheet

Jun 2014

Deals with the maintenance phase of soil fertility management for forages, including potassium.
Potassium Fertilizer Application in Crop Production Alberta Ministry of Agriculture and Forestry Governmental Fact Sheet

Jan 2013

Discusses use of potassium in crop production.
Title Source Resource type and Date Short Summary
Soil Sampling for P, K, and Lime Recommendations Purdue University Extension Publication

Feb 1995

Publication examines field crop soil sampling considerations (including potassium).
Laboratory Analysis of Manure University of Missouri Extension Webpage

Nov 2018

To make efficient use of fertilizer nutrients in manure, nutrient levels must be determined by laboratory analysis. This publication outlines methods for obtaining and interpreting laboratory analyses of manure.

Technical review: April 13, 2020