Potassium cycle

Potassium is one of the major nutritional elements in soil, Sparks and Huang (1985) describe its role in the biosphere as ‘prodigious’. Its chemical symbol K is taken from Kalium, the German term for the element, derived from the word alkali. K influences the osmotic relations between plant and soil, functions in respiration and photosynthesis, and is an enzyme activator.

The word alkali was introduced by the Arabs to signify the ash of vegetable matter. Incineration of marine vegetation yields predominantly sodium carbonate, while terrestrial vegetation gives potassium carbonate. It was not until the eighteenth century that the two were distinguished from each other. Together they were considered fixed alkali, by contrast to ammonium carbonate, which was called volatile alkali. A further distinction was made by the Arabs between mild alkali (carbonate) and caustic alkali (hydroxide). Davy isolated the element potassium electrochemically in 1807 and derived its name from “pot ashes”,...