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Kinetics of Nonexchangeable Ammonium Release from Soils
Author(s) -
Steffens D.,
Sparks D. L.
Publication year - 1997
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/sssaj1997.03615995006100020012x
Subject(s) - alfisol , soil water , chemistry , ammonium , kinetics , environmental chemistry , mineralogy , nuclear chemistry , soil science , geology , physics , organic chemistry , quantum mechanics
The rate of nonexchangeable NH 4 + release from soils can have a significant effect on N dynamics and environmental quality. Nonexchangeable NH 4 + is that N fraction which is fixed in the interlayers of clay minerals. The objective of this study was to determine the kinetics of nonexchangeable NH 4 + release from two topsoils from Germany [Giessen Ap (Aqualf) and Hungen Ap (Alfisol)] and from two subsoils, one from Germany [Hungen C (Alfisol)] and one from Kentucky [Shrouts Bt (Hapludalf)]. Calcium‐saturated, freeze‐dried soils were extracted with H‐resin for 0.25 to 384 h. Sodiumethylmercurythio‐salisylate (Thimerosal) was added to the soil/H‐resin suspension to inhibit microbiological ammonification. The kinetics of nonexchangeable NH 4 + release from the soils were biphasic and were best described by Elovich and heterogeneous diffusion models. The release of nonexchangeable NH 4 + as a percentage of total nonexchangeable NH 4 + in the soils ranged from 4 to 25% and was lower in subsoils than in topsoils. This was ascribed to the higher levels of indigenous nonexchangeable NH 4 + in the subsoils, which is more tightly held than recently fixed nonexchangeable NH 4 + .