Muriate of potash (MOP) is most commonly called potash or potassium chloride (KCL), it is the third largest crop nutrient group, next to nitrogen and phosphorous. Muriate of potash (MOP) is most commonly called potash or potassium chloride (KCL), it is the third largest crop nutrient group, next to nitrogen and phosphorous. 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.