Nitrogen transformations and loss in flooded soils and sediments

Abstract

This paper presents a critical review on nitrogen (N) transformations functioning in flooded soils and sediments, and their role in N loss from the system. Nitrogen transformations reviewed include (1) ammonification (organic ? ammonium N) (2) nitrification (ammonium ? nitrate), (3) ammonia volatilization (ammonium N ? NH3), (4) denitrification (nitrate ? gaseous products N2O and N2). Transport processes reviewed were ammonium and nitrate diffusion. Inorganic N in flooded soils and sediments and waters is converted to gaseous forms by two processes, i.e., (1) nitrification‐denitrification; and (2) NH3 volatilization. The former process seems to be more predominantly involved in the ammonium N loss from the sediments, whereas the latter process occurs under specialized conditions, mainly in the overlying waters. The processes involved in converting organic N to gaseous end products include ammonification of organic N to ammonium N, upward diffusion of ammonium N into the aerobic soil layer, oxidation of am...