State about the importance of Potassium 

Potassium is the third major element required for plant growth, generally absorbed as K⁺ ion. In soil 95 to 99 percent of potassium exists in the lattice of minerals like feldspar, muscovite, biotite and hydrous mica. The Earth's crust has an average potassium content of 2.6 percent. This would easily mean that it contains 40,000 to 50,000 kilograms of potassium per hectare. This amount of potassium is sufficient to last forever. However, this potassium is not readily available, hence money spent for potassium fertilizers is constantly on the increase.