Geoscience Reference
In-Depth Information
from the surface horizons. Hydrogen and aluminium ions appear on
the exchange complex. Only the B horizons remain alkaline. Nowadays
these soils are grouped under
Glossalbic Solonetz
.
Solonetz and Solods are rarely cultivable and are often left to
extensive pasture.
In the WRB, the classification of subtypes is done by considering
accessory characteristics, particularly,
morphology (Albic, Humic, Histic, Vertic, etc.),
texture (Arenic, Siltic, Clayey, etc.),
hydromorphy (Gleyic, Stagnic, etc.),
chemistry (Gypsic, Chloridic, Sulphatic, Calcaric, etc.).
13.5.3 Groupings in Soil Taxonomy
Soil Taxonomy does not group saline soils separately. It considers that
salinity corresponds to a property that may occur in various Orders.
Therefore it is necessary to concern ourselves with the following
diagnostic horizons:
Salic horizon
that contains salts more soluble than gypsum
,
Natric horizon
, in which is found columnar structure, ESP >
15 or a value greater than 1 for the ratio [(Mg + Na)/(Ca +
exchangeable acidity)]. But our summarized definition is only
approximate,
Gypsic horizon
that contains gypsum precipitated
in situ
,
Petrogypsic
that, in addition, is hardened,
Also the adjective
halic
must at times be used which, in
Hal-aqu-epts for example, signifies ESP > 15.
Saline soils are found in various Orders, especially: Inceptisols
(immature soils), Entisols (scarcely developed soils), Aridisols (soils of
arid regions) and Alfisols (argilluviated soils). Presence of salts appears,
as the case may be:
at the Suborder level, for example Sal-ids (with salic horizon) or
Gyps-ids (with gypsic or petrogypsic horizon),
at the Great Group level, as for example in Sal-orth-ids
(Solonchaks), Natr-arg-ids (Solonetz) or Gypsi-arg-ids,
At the Subgroup level, for example in Sodic Haplo-calc-ids, Sodic
Psamm-aqu-ents, Sodic Calci-xer-epts, etc.
It is difficult to account for salinity when it affects Mollisols (Rogel
et al
. 2001a). For finding all these names, refer to Chapter 4 (§ 4.3).