Michigan State University Extension
Soils & Soil Management - Fertilizer - 06109729
07/10/97
N-P-K Fertilizers Extension Bulletin E-896, October 1990
by M.L. Vitosh Extension Specialist, Crop and Soil Sciences
Potassium chloride (60 to 62% K2O), also referred to as muriate of potash, is the major source of K used in Michigan. Nearly two-thirds is used for direct application, and the remainder is used in granulating processes or bulk blending of mixed fertilizers. It is available in four particle sizes: fine, standard, coarse and granular. The fine-size material is used primarily for liquid suspensions. Standard, coarse and granular sizes are used for granulating processes, bulk blending and direct application. Potash varies in color from pink or red to white depending on the mining and recovery process used. White potash, sometimes referred to as soluble potash, is usually higher in analysis and is used primarily for making liquid starter fertilizers.
Potassium sulfate (50% K2O), also referred to as sulfate of potash, is used to a limited extent on crops such as tobacco, potatoes and a few vegetable crops where chloride from potassium chloride might be undesirable. Potassium sulfate in some research studies has improved specific gravity of potato tubers. Potassium sulfate may also be a source of sulfur when sulfur is required.
Potassium magnesium sulfate (22% K2O), also known as sulfate of potash magnesia, is used for both direct application and in bulk blending, particularly where magnesium is needed. It may also be used as a source of sulfur.
Potassium hydroxide, also known as caustic potash, is used to a limited extent in the production of liquid mixed fertilizers. The present cost of producing potassium hydroxide has limited its use in the fertilizer industry, even though it is a very desirable product due to high solubility and low salt index.
Potassium nitrate (44% K2O), also known as nitrate of potash, is being used in Michigan primarily on high value crops such as celery, tomatoes, potatoes, leafy vegetables and a few fruit crops. It has a low salt index and provides nitrate N which may be desirable for these specialty crops. Production costs have limited general use for most agronomic field crops.
MSU is an affirmative-action/equal-opportunity institution. Extension programs and materials are available to all without regard to race, color, national origin, sex, disability, age, religion, or handicap. Issued in furtherance of the Cooperative Extension work in agriculture and home economics, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Arlen Leholm, interim extension director, Michigan State University, E. Lansing, Ml 48824. This information is for educational purposes only. References to commercial products or trade names does not imply endorsement by the MSU Extension or bias against those not mentioned. This bulletin becomes public property upon publication and may be printed verbatim with credit to MSU. Reprinting cannot be used to endorse or advertise a commercial product or company. Produced by Outreach Communications and printed on recycled paper using vegetable-based inks.
Reprint-7:96-5M-TCM-SP-Price 35 cents. File 32.331 (Fertilizers)