I'm doing classification for soils have more than 30 % of CaCO3, located in arid and semi arid conditions Could you please give me your opinion if i have a calcic horizon or not?
According to WRB-SR a calcic horizon has more than 15% CaCO3 and more than 5% secondary carbonates. So it seems quite obvious that you have calcic horizons. However, you need to make sure that you have indeed secondary carbonates and not just a calcareous parent material.
Dear Patriche
Thank you very much , with WRB -really i have calcic horizon
With keys soil taxnomy 2010 , most soil profiles have not calcic horizon and it could be in an anther order .
Could you please gave your openion?
Hello,
I think that the key factor is the detection of secondary carbonates in the soil matrix (if requirements according to thickness and quantity are fulfilled). This can be detected in field by the presence of accumulations in several forms (nodules, pseudo-myceliums, etc) that usually can be observed with a naked eye. The increase in CaCO3 content in an horizon (5%) in relation to an an underlying horizon is also determinant. In some soils it is not so easy, in that cases the micromorphological study by petrographic microscope is required to identify the specific pedofeatures of secondary precipitation of carbonates.
Thanks .,
Calcic Horizon
The calcic horizon is an illuvial horizon in which secondary
calcium carbonate or other carbonates have accumulated to a
significant extent.
Required Characteristics
The calcic horizon:
1. Is 15 cm or more thick; and
2. Has one or more of the following:
a. 15 percent or more (by weight) CaCO3 equivalent (see
below), and its CaCO3 equivalent is 5 percent or more
(absolute) higher than that of an underlying horizon; or
b. 15 percent or more (by weight) CaCO3 equivalent
and 5 percent or more (by volume) identifiable secondary
carbonates; or
c. 5 percent or more (by weight) calcium carbonate
equivalent and:
(1) Has less than 18 percent clay in the fine-earth
fraction; and
(2) Meets the criteria for a sandy, sandy-skeletal, coarseloamy,
or loamy-skeletal particle-size class; and
(3) Has 5 percent or more (by volume) identifiable
secondary carbonates or a calcium carbonate equivalent
(by weight) that is 5 percent or more (absolute) higher
than that of an underlying horizon; and
3. Is not cemented or indurated in any part by carbonates, with
or without other cementing agents, or is cemented in some part
and the cemented part satisfies one of the following:
a. It is characterized by so much lateral discontinuity that
roots can penetrate through noncemented zones or along
vertical fractures with a horizontal spacing of less than 10
cm; or
b. The cemented layer is less than 1 cm thick and consists
of a laminar cap underlain by a lithic or paralithic contact; or
c. The cemented layer is less than 10 cm thick.
Key soil taxnomy 2010
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