1. Answer questions a through g based on the descriptions of the horizons in the
ID: 575 • Letter: 1
Question
1. Answer questions a through g based on the descriptions of the horizons in the soil profile in the box below.
Location Soil Profile and Land Use of the Area : A former wetland area that had been drained and cultivated
Surface
_____ --0-6 inches; well-decomposed deciduous leaves, roots
2nd horizon
_____ --6 to 10 inches; dark yellowish brown (10YR 4/4); sandy loam; weak medium granular structure; very friable; slightly acid
3rd horizon
_____ --10 to 26 inches; very dark gray (10YR 5/1); clay; moderate medium subangularblocky structure; firm; sticky, plastic; common clay films on faces of peds
4th horizon
_____ --26 to 42 inches; dark gray (10YR 4/1); clay; few fine prominent yellowish red (5YR 5/8) mottles; moderate medium subangular blocky structure; firm; sticky, plastic; common clay films on faces of peds
5th horizon
_____ --42 to 80 inches; light gray (10YR 7/1); loam saprolite; common medium distinct pale yellow (2.5Y 7/4) and common distinct brown (7.5YR 5/4) mottles; massive.
What subordinate distinctions (lowercase letters) would be appropriate for the surface horizon? ________ ( 1 pt)
What subordinate distinction is appropriate to indicate the change in clay content? ____ (1 pt)
Surface
_____ --0-6 inches; well-decomposed deciduous leaves, roots
2nd horizon
_____ --6 to 10 inches; dark yellowish brown (10YR 4/4); sandy loam; weak medium granular structure; very friable; slightly acid
3rd horizon
_____ --10 to 26 inches; very dark gray (10YR 5/1); clay; moderate medium subangularblocky structure; firm; sticky, plastic; common clay films on faces of peds
4th horizon
_____ --26 to 42 inches; dark gray (10YR 4/1); clay; few fine prominent yellowish red (5YR 5/8) mottles; moderate medium subangular blocky structure; firm; sticky, plastic; common clay films on faces of peds
5th horizon
_____ --42 to 80 inches; light gray (10YR 7/1); loam saprolite; common medium distinct pale yellow (2.5Y 7/4) and common distinct brown (7.5YR 5/4) mottles; massive.
Explanation / Answer
The following are descriptions of the Master Soil Horizons (upper case) and Subordinate Horizon
Designations (lower case) that may be applied to them. For cases in which a layer of soil has
charactersistics of more than one Master Soil Horizon, the rules for assigning transitional horizons are
provided in a section at the end.
O horizons or layers: Surface layers of organic material accumulated on top of the surface of either
mineral or organic soil. O horizons may consist of undecomposed or partially decomposed litter,
such as leaves, needles, twigs, fruit, moss, and lichens. Other O layers, called peat, muck, or
mucky peat, are organic material that was deposited underwater and that has decomposed to
varying stages. The mineral fraction of such material is only a small percentage of the volume of the
material and generally is much less than half of the weight. Some soils consist entirely of material
designated as O horizons or layers. A horizon formed by illuviation of organic material into a
mineral subsoil (e.g. Bh) is not an O horizon, though some horizons formed in this manner contain
much organic matter.
a Highly decomposed organic material of unidentifiable origin.
e Organic material of intermediate decomposition; identifiable; fragmented.
i Slightly decomposed organic material; identifiable; slightly fragmented.
A horizons: Mineral horizons that formed at the surface or below an O horizon and (1) are
characterized by an accumulation of humified organic matter well mixed with the mineral fraction and
not dominated by properties characteristic of E or B horizons (defined below) or (2) have
properties resulting from cultivation, pasturing, or similar kinds of disturbance. If a surface horizon
has properties of both A and E horizons but the feature emphasized is an accumulation of humified
organic matter, it is designated an A horizon.
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