Potash fertilizers: What is sulfate of potash?
SOP is considered a premium-quality potash. It contains two key nutrients for growing crops: potassium and sulfur. Using SOP improves both quality and crop yields and makes plants more resilient to drought, frost, insects and even disease. SOP can improve the look and taste of foods and boost a plant’s ability to absorb key nutrients like phosphorus and iron.
Most often, SOP is used on high-value crops like fruits, vegetables, nuts, tea, coffee and tobacco. It works better on crops that are sensitive to chloride, which can be toxic to some fruit and vegetable plants.
SOP is not a naturally occurring mineral, and usually must be produced through chemical methods. Because of the resource-intensive processes used to create it, SOP is priced higher than MOP. The most common method used to produce the fertilizer SOP is called the Mannheim process. It involves pouring potassium and other raw minerals into a muffle furnace that is heated above 600 degrees Celsius, creating a reaction between potassium chloride and sulfuric acid. Fertilizer produced like this accounts for roughly 50 to 60 percent of global SOP supply.
The second most common way of making SOP, accounting for about 25 to 30 percent of supply, is by reacting potassium chloride with various sulfate salts to form what is called a double salt.
“The most common raw material employed for this purpose is sodium sulfate. Sodium sulfate, either in the form of mirabilite (also known as Glauber’s Salt) or sulfate brine, is treated with brine saturated with MOP to produce glaserite,” Kalium Lakes (ASX:KLL,OTC Pink:KLLKF), a Western Australia-focused SOP company, explains on its website. “The glaserite is separated and treated with fresh MOP brine, decomposing into potassium sulfate and sodium chloride.”
There are also operations that produce this type of potash fertilizer by using salt mixtures from natural brines. This requires brine with high sulfate levels that are typically found in salt lakes. Companies able to use naturally occurring brines include Compass Minerals International (NYSE:CMP), which operates out of Overland Park in Kansas, and Chile’s SQM (NYSE:SQM), which has operations in the Salar de Atacama. SQM is a major producer of lithium as well.
There are also smaller potash fertilizer companies that eventually plan to produce SOP, including Agrimin (ASX:AMN) which says its Mackay project in Western Australia will be shovel ready in 2024.
