Potassium chloride (commonly referred to as Muriate of Potash or MOP) is the most common potassium source used in agriculture, accounting for about 95% of all potash fertilisers used worldwide.

Its nutrient composition is approximately:

POTASSIUM.: 50%

CHLORIDE.: 46%

MOP has a high nutrient concentration and is therefore relatively price competitive with other forms of potassium. The chloride content of MOP can also be beneficial where soil chloride is low. Recent research has shown that chloride improves yield by increasing disease resistance in crops. In circumstances where soil or irrigation water chloride levels are very high, the addition of extra chloride with MOP can cause toxicity. However, this is unlikely to be a problem, except in very dry environments, since chloride is readily removed from the soil by leaching.