Premium
Ammonium Diffusion as a Factor in Nitrogen Loss from Flooded Soils
Author(s) -
Reddy K. R.,
Patrick W. H.,
Phillips R. E.
Publication year - 1976
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1976.03615995004000040023x
Subject(s) - nitrification , soil water , ammonium , denitrification , chemistry , anaerobic exercise , nitrogen , soil horizon , diffusion , environmental chemistry , soil science , environmental science , thermodynamics , physiology , physics , organic chemistry , biology
The role of NH 4 + ‐N diffusion in a flooded soil on nitrogen (N) loss through the nitrification‐denitrification process was investigated under laboratory conditions. The distribution of applied NH 4 + ‐N in both the aerobic and anaerobic soil layers of a flooded soil was experimentally determined and compared with the values obtained from theoretical equations. The total loss of NH 4 + ‐N from the flooded soil system (15‐cm depth) by nitrification‐denitrification was equivalent to 12.43 g N/m 2 for a 120‐day incubation period when the initial concentration of NH 4 + ‐N was 44.84 g N/m 2 . Diffusion of NH 4 + ‐N from the anaerobic soil layer to the aerobic soil layer accounted for more than 50% (7.16 g N/m 2 ) of the total NH 4 + ‐N loss with the remainder being lost from NH 4 + ‐N originally present in the aerobic layer. The NH 4 + ‐N that diffused upward into the aerobic soil layer was nitrified to NO 3 ‐ ‐N, which readily diffused back down into the anaerobic soil layer and was subsequently denitrified. The experimental distributions of NH 4 + ‐N were not in close agreement with calculated distributions in the surface aerobic soil layer, but were in close agreement in the anaerobic soil layer. It is possible that the rate constant ( k ) for NH 4 + ‐N oxidation varied considerably with depth in the aerobic soil layer and thus resulted in the disagreement. The total NH 4 + ‐N loss calculated from the experimental distributions tended to agree with the values obtained theoretically from rate constant ( k ) values of 3.18, 5.00, and 6.67 µg cm ‐3 day ‐1 . The first rate constant value was obtained from an independent experiment (for same soil), the second from matching the concentration of NH 4 + ‐N at the aerobic‐anaerobic layer interface of the theoretical and experimental distribution at 90 days after flooding, and the third from the NH 4 + ‐N disappearance in the aerobic soil layer of the soil columns described in this study. These rate constants indicate that the rate of nitrification is one of the factors controlling N loss from flooded soil.