Geoscience Reference
In-Depth Information
Furthermore, Solonchaks have variable morphology:
gleyic
character
or none, possible accumulation of humus (
humic
), with sulphates or
sulphides (
thionic
), etc. In the coastal environment, the annual renewal
of salts by marine submergence in winter saves these soils from
complete alkalization and hinders them from evolving into other more
differentiated types. But biological activity remains low.
The word comes from the Russian
sol
(salt) and
etz
(strongly expressed).
These soils are rich in Na
2
CO
3
but are often non-saline with low
electrical conductivity, contrary to what their name suggests. They have
a
natric
horizon (WRB). This horizon is clayey; it is usually located
below an A horizon; its structure is columnar or prismatic; it is massive;
without exception it contains more than 15 per cent Na
+
on the exchange
complex. The pH is high (higher than 8.5 and going up to 10). The
clay, deflocculated because of the sodium, is washed downward and
eventually destroyed by alkalinolysis. Thus Solonetz have the appearance
of clay-leached soils with well-contrasted horizons (Fig. 13.16). They are
found under continental steppe climate in Australia, Africa, southern
countries of the former USSR, etc.
Solonetz
Black thin layer with efflorescence of Na CO and dissolution of organic matter
2
3
A
E
Albic horizon:
depleted of fine elements and salts; poorly structured
Natric horizon:
often clay-rich and with a characteristic
structure; it generally presents rust-coloured mottles (segregation of
iron), calcium carbonate concretions and clay coatings (seen in thin
section)
columnar
B
Iron
C
CaCO
3
Fig. 13.16
Solonetz profi le.
Considering what has been said earlier in regard to precipitation of salts,
Solonchaks often contain, in addition,
calcic
or
gypsic
horizons. They can
also show other properties that bring them closer to soils with excess
water, vertic soils and others.
Earlier, we used to call
Solod
or
Soloth
or
Solodized Solonetz
the
specifically evolved Solonetz in which the E horizon is thick and very
white, while the B horizons are compacted, lose their good prismatic
structure and become impermeable. The boundary between the two
is abrupt, as in Planosols (Bertrand 1981). At this stage, sodium is lost
Other types
