Agricultural Uses

Eh is the voltage difference between a reference electrode for hydrogen and a calomel electrode in a solution. It represents differences in the redox potential of an oxidation-reduction system. The voltage difference between a hydrogen electrode and calomel electrode is 0.248 V.
Eh is used to study redox potential of a system. Thus, in the soil, there is exchange of electrons between redox systems like Fe²⁺/Fe³⁺,Mn²⁺/Mn⁴⁺ and the potential difference varies between 900mV and 300mV. The variation in Eh depends on several factors such as the concentration of the metal, moisture content, pH, organic matter content and the presence of microflora.