Potassic fertiliser containing maximum quantity of potash is

Potassium fertilizer containing the maximum quantity of potash is Muriate of potash.
It usually contains 60% K₂O. It is the most common source of potash for farm use and is also the main potash ingredient for compound fertilizers containing potassium.
MOP (Muriate of Potash) is a red-white crystal, completely soluble in water and therefore readily available to the crops.