Photo: 60% Muriate of Potash

Potassium

We typically use muriate of potash which has an analysis of 0-0-60.  Potash is the ingredient needed in the highest volume for most plants.  It helps with heat and cold stress, resistance to pathogens and gives strength to the plant cell walls.  It is most important to broadleaf dicots, like alfalfa and clover.  Similar to Phosphate, but much less severe, Potassium (K) has loading ratio for plant availability.  In low soil ranges with a soil K of 50-75, 8lb. of applied product will raise the soil K level by 1lb.  In the medium range, around 150lb of soil K per acre, 5.5lb. of applied product is needed to increase the soil level K by 1lb. 

If you are interested in a more indepth explaination, you may like this link:  www.spectrumanalytic.com/doc/library/articles/potassium_basics

You may also be interested in these articles:  www.southernstates.com/articles/potash-us.aspx