Potassium as a metal is extracted from the electrolysis of its hydroxide, potassium hydroxide. This process has changed little since Sir Humphry Davy discovered potassium by the electrolysis of its molten salt in 1807. Potassium is abundant in plants, while sodium metal, also in the same family on the periodic table, is low. The ash of plants was originally leached with water, which removed the potassium from the ashes, and allowed to precipitate upon the waters evaporation, hence the early name "potash". Soils may be severely depleted of their potassium levels with heavy agricultural use. Up to 93% of chemical potassium is used for commercial fertilizer preparation. Potassium is in the same group as sodium metal, the alkaline metals, which are violently reactive with water. Potassium, like sodium, must be stored under organic compounds to preserve it from interacting with water from the atmosphere.