How does soil redox potential affect the rate of denitrification?
Denitrification requires anoxic conditions, organic matter, and NO3-. 

Gleysols are anoxic soils formed in wetlands. Waterlogged wetland soils are generally both anaerobic and high in organic matter. For a given concentration of NO3-, denitrification rates should be higher in Gleysols than similar soils that are aerobic soils (because there will be less organic substrate and less anaerobic habitat).

Notably, even in aerobic soils, denitrification can occur within anaerobic microsites.

references: 


Bedard-Haughn 2010. Prairie Wetland Soils in Prairie Soils and Crops Journal (pdf)
Schlesinger and Bernhardt 2013 Biogeochemistry 3rd Edition p 205-208