This pit could only be dug 14 inches deep because of the limestone bedrock.
Lithologic Discontinuity
In some soils the C horizon is a parent material unlike the parent material
which formed the A and B horizons. The presence of this second parent material
is called a lithologic
discontinuity. This is common in Minnesota because of
glaciation. Many of our soils will have more than one parent material (PM).
When describing soils that have more than one PM, the first PM is not labeled
in the horizon designation, but where the second PM starts, a
"2" is put in front of the
letter designation (eg. A1, A2, 2R).
This pit could only be dug 14 inches deep because of the limestone bedrock.
Numbering Horizons
When a thick horizon is not exactly the same in all parts, the horizon
can be divided into sections by numbering the divisions. The number of
divisions will depend on the purpose of the soil description. A a soil with a
very thick A layer could have an A1, A2, A3, A4 sequence of horizons. A
soil with a thick Bt might have a Bt1 and a Bt2. In general
"lumpers" have only a few horizons
and "splitters" have a lot.
This soil has two "Bg" horizons. The g subscript is used for horizons that are
gleyed in color because of a reduced chemical condition because of a lack of
oxygen due to excess water. The g indicates a gray-colored horizon.
Virgule " / " for Transition Horizons
Transitions horizons have a mixture of two horizons rather than a gradual
change from one to the other. Parts of the B and E horizon are very evident in
the E/B horizon.
This is very common in Udalfs of northern Minnesota, due to the interfingering
of the E down into the B horizon in the zone immediately below the E horizon.
Transition horizons without the "/" (a regular "EB") are a
zone of the soil with a gradual change from the bottom of the E to the top of
the B.
Use of & and '
In some soils the horizons are repeating because of their unique formation
processes. In sandy soils, the accumulation of iron and clay often occurs in
thin bands called lamellae. Lamellae
are 1 to 5 cm thick and repeat at intervals of 5 to 50 cm. The zone where the E
and Bw material is repeating is called a "E &
B" horizon. The Zimmerman soils of the Anoka Sand Plain have
this horizon designations.
The arrow points at the Bw part of the E&B, and the E is the light area
below the Bw.
The ' is used for the second time a horizon is present in the same profile, or the second sequence of horizonation. This kind of soil is said to have a bisequum profile ( See the picture of theItasca soil for use of prime ' ). A typical sequence might be A, E, Bw, E', E/B, Bt, C for a bisequum soil.
If you go to the NRCS in Washington, you can look at the official soil series descriptions for all of the soils in the US. I want you to check out the official series description for the Clarion, Webster, Lester, and Nashwauk soils at this location. Just type in the soil name. Official Series Descriptions
Look at the following: note the Clarion has 3 A horizons, 2 Bw's, and 2 C's; for the Webster, note the use of the Bg; for the Lester, note the use of the transition BE and 3 Bt's; for the Nashwauk, note the bisequum profile and use of E'.
For more practice at looking at soil profiles with the horizon designations go to Soil Orders.
Soil Judging at the University of Minnesota.
Soil judging is an activity sponsored by the Department of Soil, Water, &
Climate and the American Society of Agronomy. Regional Contests are held in the
fall and the national contest is in the spring. For information see
Soil Judging U of M
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