Reduction of nitrate and sulfate in submerged soils with special reference to redox potential and water-soluble sugar content of soils

The ability of the soil to reduce some substances under submerged condition is one of the important soil properties in the management of lowland rice fields. The author thinks that this ability can be indicated by the reduction rate of the oxidized form of some substances in soils under submerged condition and can be called the reducing ability of the soil. This ability is thought to be related to the state of reduction of soil and the amount of hydrogen donors and their precursors for the reduction. The state of reduction can be indicated by the redox potential. The author selected the watersoluble sugar as the example of the hydrogen donor or their precursor, because appreciable amounts of carbohydrates, water soluble and insoluble, are present in soils. To elucidate the relationships between the redox potential, the water soluble sugars and the reducing ability of the soil, the following experiments were carried out, using the soils incubated in a laboratory and from a lowland rice field.