Potassium (K) fertilizer is commonly added to improve the yield and quality of plants growing in soils that are lacking an adequate supply of this essential nutrient. Most fertilizer K comes from ancient salt deposits located throughout the world. The word “potash” is a general term that most frequently refers to potassium chloride (KCl), but it also applies to all other K-containing fertilizers, such as potassium sulfate (K₂SO₄, commonly referred to as sulfate of potash, or SOP).
Agricultural use
Potassium is needed to complete many essential functions in plants, such as activating enzyme reactions, synthesizing proteins, forming starch and sugars, and regulating water flow in cells and leaves. Often, concentrations of K in soil are too low to support healthy plant growth.
Potassium sulfate is an excellent source of K nutrition for plants. The K portion of the K₂SO₄ is no different from other common potash fertilizers. However, it also supplies a valuable source of S, which protein synthesis and enzyme function require. Like K, S can also be too deficient for adequate plant growth. Further, Cl- additions should be avoided in certain soils and crops. In such cases, K₂SO₄ makes a very suitable K source.
Potassium sulfate is only one-third as soluble as KCl, so it’s not as commonly dissolved for addition through irrigation water unless there’s a need for additional S.
