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Soil Classification Data
Unified Soil Classification System
Compiled by B. W. Pipkin, University of Southern California
More than half of
material is larger than
no. 200 sieve size
More than half of
material is smaller than
no. 200 sieve size
Checklist for Field Descriptions of Soils
Roy W. Simonson. Principal sources are U.S. Department of Agriculture Handbooks 18 and 436.
GENERAL INFORMATION AND SETTING
IDENTIFICATION: Name of soil series or broader class, as specific as feasible.
PHYSIOGRAPHY: Such as till plain, high terrace, flood plain.
UNDERLYING MATERIALS: General nature, such as calcareous clayey till or residuum from granite.
SLOPE: Approximate gradient.
PLANT COVER: Vegetation at site, such as oak-hickory forest, corn, pasture.
MOISTURE STATUS: Conditions at the time, such as wet, moist, dry.
REMARKS: Other features such as stoniness, salinity or depth to ground water; not applicable or observable everywhere.
DESCRIPTIONS OF INDIVIDUAL HORIZONS
DESIGNATION: See hypothetical soil profile, Data Sheet 36.
DEPTH: cm (or inches) from top of a horizon and from surface of organic soil.
THICKNESS: Average, such as 15 cm, plus range, such as 10-20 cm.
BOUNDARY: Lower one, as to distinctness: abrupt, clear, gradual, or diffuse; and as to topography: smooth, wavy, irregular or broken.
COLOR: Record colors of both wet and dry specimens if possible, but always for wet conditions. Use number-letter notations from Munsell Soil Color charts, e.g., lOYR 5/4. Record mottles (patches of one color in matrix of another color) as to abundance: few, common, many; as to size: fine, medium, coarse; and as to contrast: faint, distinct, prominent.
TEXTURE: Classes should show relative proportions of the separates sand, silt, and clay. See triangular graph showing textures, Data Sheet 37.2.
STRUCTURE: Describe natural units as to grade (distinctness): weak, moderate, strong; as to size: very fine, fine, medium, coarse, very coarse; and as to type: platy, prismatic, blocky, granular. Without peds, horizon can be either single-grained or massive.
CONSISTENCE: Cohesion, adhesion, and resistance of specimens to deformation and rupture. When wet: nonsticky, slightly sticky, sticky, or very sticky; also: nonplastic, slightly plastic, plastic, or very plastic. When moist: loose, very friable, friable, firm, very firm, or extremely firm.
When dry: loose, soft, slightly hard, hard, very hard or extremely hard.
ROOTS: Numbers of observable roots: few, common, or many; and dimensions: fine, medium, or coarse.
PORES: Numbers of field-observable pores: few, common or many; dimensions: very fine, fine, medium, or coarse; and shapes: irregular, tubular or vesicular.
REACTION: pH as measured with field kit.
ADDITIONAL FEATURES: Other features if present, such as iron or carbonate concretions (use same abundance and dimension classes as for roots), effervescence with dilute HCI, krotovinas (filled animal burrows), cementation (weakly, strongly, indurated), and stone lines.
Particle Size Descriptions
|Size Term||Particle Diameter|
|Boulder||> 256 mm|
|Cobble||64 to 256 mm|
|Pebble||4 to 64 mm|
|Granule||2 to 4 mm|
|Very Coarse Sand||1 to 2 mm|
|Coarse Sand||1/2 to 1 mm|
|Medium Sand||1/4 to 1/2 mm|
|Fine Sand||1/8 to 1/4 mm|
|Very Fine Sand||1/16 to 1/8|
|Silt||1/256 to 1/16 mm|
|Clay||< 1/256 mm|
|Bomb or block||> 32 mm|
|Lapilli||4 to 32 mm|
|Coarse Ash||1/4 to 4 mm|
|Fine Ash||< 1/4|
|Pegmatitic||> 30 mm|
|Coarse Grained||5 to 30 mm|
|Medium Grained||1 to 5 mm|
|Fine Grained||< 1 mm|