MOP vs SOP Potash: Product, Nutrient Basis and Buyer Fit
The commercial and agronomic distinction between muriate of potash and sulfate of potash, without treating them as interchangeable price series.
Last reviewed
MOP and SOP both supply potassium. They are different chemical products with different secondary nutrients, chloride content, use cases, customs classifications, production routes, and price bases.
MOP: muriate of potash
MOP is the common fertilizer name for potassium chloride, KCl. The U.S. Geological Survey describes fertilizer-grade MOP as an agriculturally acceptable mixture based on high-purity potassium chloride. Commercial grades are often expressed as potassium oxide equivalent, not as elemental potassium.
MOP is widely used because it is a concentrated and broadly available potassium source. The Government of Manitoba describes KCl 0-0-60 as the least expensive and most readily available form of potassium fertilizer in its potato-production guidance, while also noting crop and application considerations related to chloride.
SOP: sulfate of potash
SOP is potassium sulfate, K₂SO₄. It supplies potassium and sulfur with much less chloride than MOP. USGS notes that SOP and potassium-magnesium sulfate are required for certain chloride-sensitive crops.
That does not mean SOP is universally “better.” Product selection depends on crop, soil, water, chloride sensitivity, nutrient plan, agronomic advice, availability, and total delivered economics.
Do not compare the sticker price alone
A buyer should normalize:
- product identity and chemical formula;
- guaranteed K₂O-equivalent content;
- sulfur or chloride content;
- standard, granular, soluble, or other form;
- particle-size distribution;
- bulk or bagged packing;
- origin and customs classification;
- quantity and delivery window;
- Incoterm, named place, and currency;
- agronomic application requirement.
A tonne of MOP and a tonne of SOP do not deliver identical nutrients. A price comparison can therefore use cost per tonne, cost per unit of K₂O equivalent, or full nutrient-plan economics depending on the decision.
Keep the data series separate
The USGS potash chapter reports product-specific and all-product statistics on stated bases. A potassium-chloride benchmark should not be labelled as a universal potash price, and it should never be presented as an SOP quote.
The same separation applies to trade data: KCl and potassium sulfate use different HS headings. Merging them can create a misleading unit value and the wrong buyer signal.
What a useful requirement says
“Need potash” is not actionable. A qualified requirement identifies MOP or SOP, grade, form, packing, quantity, destination, delivery window, allowed origins, Incoterm, and proposed payment approach.
GMC’s potash sector page describes the qualification scope. It does not imply standing allocation or a current producer mandate.
Is MOP the same as potash?
MOP is one major potash fertilizer product. “Potash” can also refer to other potassium-bearing products. A buyer should name the chemical product and grade rather than rely on the category name.
Which is better, MOP or SOP?
Neither is universally better. MOP is often the lower-cost potassium source. SOP supplies sulfur and much less chloride. Crop sensitivity, soil, water, application and nutrient plan decide the agronomic fit.
How should the price comparison be made?
Compare the same delivered basis and show cost per tonne, guaranteed K₂O-equivalent content and any other nutrient value the decision uses. The potash intelligence page covers Canadian HS 310420 potassium chloride trade. It does not label that series as SOP or a live quote.
Sources and review record
These are the primary or authoritative sources used for this explainer. Listing a source does not imply endorsement of GMC.
- Mineral Commodity Summaries 2026: Potash U.S. Geological Survey · reviewed August 26, 2026
- Guide to Commercial Potato Production on the Canadian Prairies Government of Manitoba · reviewed August 26, 2026