Oxidation-reduction potential of a paddy soil inin situwith special reference to the production of ferrous ikon, manganous manganese and sulfide

Paddy fields are kept in a flooded condition for at least three months during the growing period of rice plants. The chemical characteristics of soils in paddy fields, therefore, are remarkably different from these of upland fields. Many soil constituents undergo great changes during the flood period. The soil can be understood as a redox system (1, 17). Japanese workers (3) have found oxidized and reduced layers in the submerged soil, which cause the soil to lose nitrogen by nitrification of ammonium and denitrification of nitrate and/or nitrite.