The oxidized and reduced layers in flooded soil were characterized by vertical distribution of the oxidation-reduction (redox) potential and concentrations of manganous manganese, ferrous iron, sulfide, nitrate and ammonium. The apparent thickness of the oxidized layer was different when evaluated by the distribution of these various components in the profile. Flood water NO3 removal rates of intermittently-flooded freshwater swamp soils and continuously-flooded saline marsh soils indicated that the area of NO3 reduction was in the soil, added organic matter increased the rate of NO3 reduction and the reduction rate was approximately twice as fast in the marsh soil as in the swamp soil. Atmospheric O2 over a flooded soil increased denitrification up to a concentration of approximately 20%. The N loss appeared to be related to the thickness of the sediments aerobic layer. Ammonium nitrogen in a flooded soil exposed to O2 from the water column undergoes sequential nitrification and denitrification. Ammonium nitrogen is nitrified in the aerobic zone, diffuses to the anaerobic zone where it is denitrified to N2 and N2O and then diffuses from the system.

"Grant no. 800428." Includes bibliographical references (pages 78-79).