D. Steffens et Dl. Sparks, Effect of residence time on the kinetics of nonexchangeable ammonium release from illite and vermiculite, J PLANT NU, 162(6), 1999, pp. 599-605
Citations number
29
Categorie Soggetti
Environment/Ecology
Journal title
JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE-ZEITSCHRIFT FUR PFLANZENERNAHRUNG UND BODENKUNDE
The fraction of nonexchangeable ammonium (NH4+) can play an important role
in N cycling of soils as a sink (fixation) or a source (release) of NH4+. R
ecently fixed nonexchangeable NH4+ especially seems to be a significant sou
rce for N release. The aim of our study was to determine the effect of resi
dence time on the kinetics of nonexchangeable NH4+ release from illite and
vermiculite. Calcium-saturated illite and vermiculite, containing NH4+ that
was "fixed" for one and 60 d, were extracted with a H-resin for 0.25 to 38
4 h. Both clay minerals "fixed" significantly more NH4+ in 60 d than in 1 d
, but vermiculite "fixed" more NH4+ than illite. The kinetics of nonexchang
eable NH4+ release from illite and vermiculite were well described by the E
lovich equation and by a heterogeneous diffusion model. In vermiculite the
percentage of nonexchangeable NH4+ release decreased from 84% to 78% when t
he time of fixation increased from 1 to 60 d. In illite time of residence h
as not influenced the complete release of newly fixed NH4+.