Few chemical products are more misunderstood or perplexing than K2SO4. For example, it is called potassium sulfate (or sulphate for the British), or sulfate of potash (SOP), potash of sulfur, arcanite, dipotassium sulfate, vitriolic tartar, and even (in its impure form) Glaser's salt.

Perhaps the confusion remains because the product is itself a mix of an acid salt and an alkaline salt. This helped to give it the medieval name of arcanum duplicatum – literally meaning double secret.

Today, SOP has few secrets, as industrial chemists have a full understanding of the world’s most popular fertilizer. Potassium sulfate is typically supplied as a white or yellowish powder (about 70% of the market), pellets, or granules.  

Its usefulness as a fertilizer has been known since ancient times, as it is (of course) high in both sulfur and potassium. These nutrients are key for quality plant growth as they will become deficient in soils after constant cropping.

Applications of SOP are therefore likely to return more in crop value than the cost of SOP fertilizer. Numerous studies have consistently shown that potassium sulfate improves crop yields, increases drought-resistance, limits disease, improves crop quality, and helps protects against frost and insects. It can also boost a plant’s uptake of other vital nutrients, such as iron and phosphorus.  

It is most commonly used on high-value crops such as vegetables, nuts, fruits, tea, coffee, and tobacco and is highly effective on plants which are sensitive to chloride.

In particular, potassium sulfate (SOP) provides numerous benefits as a fertilizer feedstock over muriate of potash (MOP). These include:

·       Lower salinity (excellent for use on salty soils)

·       Added sulfur (for an additional boost to crop growth)

·       Reduced chlorides (to help avoid chemical toxicity in soils)

Confusion over SOP prices

Historically, the price of SOP has not fluctuated too dramatically, especially when compared to other significant raw materials such as oil, gold, or rare earth elements. However, the price has shifted from about US$550 a metric tonne in 2011 to more than US$700 in 2020.

Since then, like many raw materials, the supply chain disruptions from the global pandemic have made pricing less predictable.

Much of the historic price uncertainty is based on not knowing exactly how much raw material remains accessible in the Earth’s crust. While the USGS tracks reserves of some industrial feedstocks, there is no single global body which stores data on global deposits of potash.

Consequently, individual countries and companies supply data to shareholders or in company reports, but without a uniform approach to estimating remaining stocks, evaluations on ease of extraction, or information on raw material quality.

Even the EU’s Minerals4U project does not supply a complete data set for Europe’s remaining resources. Further exploration of reserves and developments in extraction techniques further cloud the issue, and while there is almost no possibility of stocks being entirely depleted this century, not knowing how much remains adds confusion to price estimates for SOP.

To receive your price quote for SOP please complete the form available through the AG CHEMI GROUP website. This will enable one of their sales team to get back to you with a price that you can trust from a dependable industrial chemical supplier, based in the heart of Europe.

You can read the second article on potassium sulfate here.

Photo credit: Vlad Chețan from Pexels, Reto Bürkler, Pexels, Mark Stebnicki, and AG CHEMI GROUP