The amount of fertilizer is determined by the content of potassium oxide. The main potassium chloride, potassium sulfate, vegetation ash, potassium salt, potassium phosphate (two potassium phosphate) and so on. Most can dissolve in water, fertilizer efficiency is quicker. And can be absorbed by the soil, not easy to lose. When the potassium fertilizer is applied in moderation, it can make the crop stalk grow strong, prevent lodging, promote flowering and fruiting, enhance drought resistance, cold resistance and insect pests and diseases ability. The unit fertilizer with potassium (K or k₂o) is potash (potash fertilizer). It can improve the potassium supplying ability of soil and the level of k nutrition of plant.

A single element "potassium" (k or K₂o) is labeled as a unit containing fertilizer (potash fertilizer), marked "potassium", and other elements are "potash". "Potash" is divided into two yuan compound potash fertilizer and ternary compound potash fertilizer.