Abstract
An investigation on the stability of the mineral
complexes in soil under natura.l and enriched chemical
H ) was
environments as (Na , , Ca , Mg ,
4
carried on for a period of about six years (1963—1969)
through a lysimeter Study involving treatments with Na ,
and NH
4
The chemical composition of the aqueous phage
was determined and was found to reflect processes of
mineral transformation and alteration.
The aqueous phase of the mineral environment was
obtained by two ways (a) displacement under
conditions (lysimetry) and (b) pressure extraction .
The stability relationship of the phases of the
system K C ..—AI O
- Sio
2
- H O, Mgo - A1 0
2
- SIO
- H 20, and
2
cao - A1 0
- Sio
- Sio
2
parameters of
H O were studied employing different ionic
the aqueous phases.
2
The zonic parameters for soil samples taken from
different parts of the profile showed kaolinite to be the
In the lower
stable phase of the clay mineral complex .
part of the profile and samples from Na treated soil
layers, a tendency was shown toward the montmorillonite
phase. These samples released greater amounts of silica
and cations indicating a more intense process of
alteration and transformation. The sodium treatment
presumably retarded the transformatibn :
Na —montmorillonite kaolinite + H SIO + Na
as Na is bnézof the products
The water samples from the Lysimeters were in
contact with the lower part
considerable period of time
showed the stability phases
montmorillonite.. The ionic
that were vertically higher
kaolihite than those the
of the soil profile for a
and the ionic parameters
of II lite and
parameters occupied positions
in the field of stability of
expressed soil solutions .
X—ray analysis of the clay fraction of the soil
samples showed the presence Of kaolinite, montmorillonite ,
micaceous clays, and quartz. Montmorillonite and micaceous
clay were apparently not in equilibrium with the ions
the aqueous phases.
It was concluded that higher concentration of
brought about gome structural dissolution of minerals
exchange with octahedral and tetrahedr I constituents
the mineral. The process gradually decreased with
of Increases o
3
e process o surface and
e p w ere
interlayer cation exchange became dominant.
The chemical composition of the aqueous phage
depicted the chemistry of the profile. This wag found Zo
be a guide for differentiation of the profile.
Another subsidiary aspect of this investigation
was the mineral nutrient losses by percolation. Soil
treatments with ammonium resulted in highest leaching
losses. Ammonium acted as mass ion, as well as a source
In general the relative ionic losses were in the
of H .
order of Na > ca > Mg > > A1 and CX->.SO - > Sio
The K treatment exhibited the highest percolation
while Na treatment showed the minimum.
A grass cropping system reduced leaching losses by
reducing percolation and increasing removal