HomeMy WebLinkAbout990667.tiff U. . -PARTMENT OF AGRICULTURE PAGE 1 OF 4
NATURAL RESOURCES CONSERVATION SERVICE 12/18/98
PHYSICAL PROPERTIES OF SOILS
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(Entries under "Erosion factors--T" apply to the entire profile. Entries under "Wind erodibility group" and
"Wind erodability index" apply only to the surface layer)
I I I (Erosion factorsiwind (wind
Map symbol I Depth I Clay Moist Permea- 'Available' Shrink- lOrganicl lerodi-Ierodi-
and soil name F bulk bility I water swell I matter' ( IbilityFbility
density I 'capacity potential' K F Kf ( T (group index
F_ I— I_J_
In Pct g/cc In/hr F In/in I I Pct I IF
F I F I
32: I F
Kim 0-12 15-27(1.25-1.40( 0.60-6.00 10.14-0.18ILow 10.5-1.01 0.371 0.371 5 ( 4L F 86
12-40 1 15-27(1.25-1.40( 0.60-6.00 (0.14-0.18ILow 10.5-1.0i 0.371 0.371 F
40-60 1 12-18(1.35-1.50( 2.00-6.00 (0.10-0.15ILow (0.0-0.5( 0.321 0.321
33:
Kim 0-12 1 15-2711.25-1.401 0.60-6.00 10.14-0.18ILow 10.5-1.0( 0.371 0.371 5 I 4L 1 86
( 12-40 1 15-2711.25-1.401 0.60-6.00 10.14-0.18ILow I0.!i-1.0( 0.371 0.371
( 40-60 F 12-1811.35-1.501 2.00-6.00 10.10-0.151Low 10.0-0.51 0.32( 0.32(
I_ 1— I I I___ I
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,TMENT OF AGRICULTURE PAGE 2 OF 4
RESOURCES CONSERVATION SERVICE 12/18/98
PHYSICAL PROPERTIES OF SOILS
Endnote -- PHYSICAL PROPERTIES OF SOILS
This report shows estimates of some characteristics and features that affect soil behavior. These estimates
are given for the major layers of each soil in the survey area. The estimates are based on field observations
and on test data for these and similar soils.
CLAY as a soil separate consists of mineral soil particles that are less than 0.002 millimeter in diameter.
In this report, the estimated clay content of each major soil layer is given as a percentage, by weight, of the
soil material that is less than 2 millimeters in diameter. The amount and kind of clay greatly affect the
fertility and physical condition of the soil. They determine the ability of the soil to adsorb cations and
to retain moisture. They influence shrink-swell potential, permeability, plasticity, the ease of soil
dispersion, and other soil properties. The amount and kind of clay in a soil also affect tillage and
earthmoving operations.
MOIST BULK DENSITY is the weight of soil (ovendry) per unit volume. Volume is measured when the soil is
at field moisture capacity, the moisture content at 1/3 bar moisture tension. Weight is determined after
drying the soil at 105 degrees C. In this report, the estimated moist bulk density of each major soil
horizon is expressed in grams per cubic centimeter of Boil material that is less than 2 millimeters in
diameter. Bulk density data are used to compute shrink-swell potential, available water capacity, total
pore space, and other soil properties. The moist bulk density of a soil indicates the pore space available for
water and roots. A bulk density of more than 1.6 can restrict water storage and root penetration. Moist
bulk density is influenced by texture, kind of clay, content of organic matter, and Boil structure.
PERMEABILITY refers to the ability of a soil to transmit water or air. The estimates indicate the
rate of downward movement of water when the soil is saturated. They are based on soil characteristics
observed in the field, particularly structure, porosity, and texture. Permeability is considered in
the design of soil drainage systems, septic tank absorption fields, and construction where the rate of
water movement under saturated conditions affects behavior.
AVAILABLE WATER CAPACITY refers to the quantity of water that the soil is capable of storing for use by
plants. The capacity for water storage is given in inches of water per inch of soil for each major soil layer.
The capacity varies, depending on soil properties that affect the retention of water and the depth cf the root
zone. The most important properties are the content of organic matter, soil texture, bulk density, and soil
structure. Available water capacity is an important factor in the choice of plants or crops to be grown and in
the design and management of irrigation systems. Available water capacity is not an estimate of the quantity of
water actually available to plants at any given time.
SHRINK-SWELL POTENTIAL is the potential for volume change in a soil with a loss or gain of moisture. Volume
change occurs mainly because of the interaction of clay minerals with water and varies with the amount and type
of clay minerals in the soil. The size of the load on the soil and the magnitude of the change in soil moisture
content influence the amount of swelling of soils in place. Laboratory measurements of swelling of undisturbed
clods were made for many soils. For others, swelling was estimated on the basis of the kind and amount of
clay minerals in the soil and on measurements of similar soils. If the shrink-swell potential is rated moderate
to very high, shrinking and swelling can cause damage to buildings, roads, and other structures. Special design
is often needed. Shrink-swell potential classes are based on the change in length of an unconfined clod as
moisture content is increased from air-dry to field capacity. The change is based on the soil fraction less
than 2 millimeters in diameter. The classes are "Low," a change of less than 3 percent; "Moderate," 3 to 6
- cent; and "High," more than 6 percent. "Very high," greater than 9 percent, is sometimes used.
9r)9 162 7
JENTOF AGRICULTURE PAGE 3 OF 4
SOURCES CONSERVATION SERVICE 12/18/98
/ PHYSICAL PROPERTIES OF SOILS
/
Endnote -- PHYSICAL PROPERTIES OF SOILS--Continued
ORGANIC MATTER is the plant and animal residue in the soil at various stages of decomposition. In report J,
wei ht, of the soil material that is
the estimated content of organic matter is expressed as a percentage, by 9
less than 2 millimeters in diameter. The content of organic matter in a soil can be maintained or increased by
returning crop residue to the soil. Organic matter affects the available water capacity, infiltration rate, and
tilth. It is a source of nitrogen and other nutrients for crops.
EROSION FACTOR K indicates the susceptibility of the whole soil (including rocks and rock fragments) to
sheet and rill erosion by water. Factor K is one of six factors used in the Universal Soil Loss Equation (USLE)
to predict the average annual rate of soil loss by sheet and rill erosion in tons per acre per year. The
estimates are based primarily on percentage of silt, sand, and organic matter (up to 4 percent) and on soil
structure and permeability. Values of K range from 0.05 to 0.69. The higher the value, the more susceptible
the soil is to sheet and rill erosion by water.
EROSION FACTOR Kf is like EROSION FACTOR K but it is for the fine-earth fraction of the soil. Rocks and
rock fragments are not considered.
EROSION FACTOR T is an estimate of the maximum average annual rate of soil erosion by wind or water that can
occur without affecting crop productivity over a sustained period. The rate is in tons per acre per year.
W_ ERODIBILITY GROUPS are made up of soils that have similar properties affecting their resistance to wind
erosion in cultivated areas. The groups indicate the susceptibility of soil to wind erosion. Soils are grouped
according to the following distinctions:
1. Coarse sands, sands, fine sands, and very fine sands.
These soils are generally not suitable for crops. They are
extremely erodible, and vegetation is difficult to
establish.
2. Loamy coarse sands, loamy sands, loamy fine sands, loamy
very fine sands, and sapric soil material. These soils are
very highly erodible. Crops can be grown if intensive
measures to control wind erosion are used.
3. Coarse sandy loams, sandy loans, fine sandy loans, and
very fine sandy loans. These soils are highly erodible.
Crops can be grown if intensive measures to control wind
erosion are used.
4L. Calcareous loams, silt loams, clay loans, and silty clay
loans. These soils are erodible. Crops can be grown if
intensive measures to control wind erosion are used.
4. Clays, silty clays, noncalcareous clay loans, and silty
clay loans that are more than 35 percent clay. These soils
are moderately erodible. Crops can be grown if measures to
control wind erosion are used.
ARTMENT OF AGRICULTURE PAGE 4 OF 4
RESOURCES CONSERVATION SERVICE 12/18/98
PHYSICAL PROPERTIES OF SOILS
Endnote -- PHYSICAL PROPERTIES OF SOILS--Continued
5. Noncalcareous loans and silt loans that are less than 20
percent clay and sandy clay loans, sandy clays, and hemic
soil material. These soils are slightly erodible. Crops
can be grown if measures to control wind erosion are used.
6. Noncalcareous learns and silt loans that are more than 20
percent clay and noncalcareous clay learns that are less than
35 percent clay. These soils are very slightly erodible.
Crops can be grown if ordinary measures to control wind
erosion are used.
7. Silts, noncalcareous silty clay loans that are less than
35 percent clay, and fibric soil material. These soils are
very slightly erodible. Crops can be grown if ordinary
measures to control wind erosion are used.
8. Soils that are not subject to wind erosion because of
coarse fragments on the surface or because of surface
wetness.
WIND ERODIBILITY INDEX is used in the wind erosion equation (WEQ) . The index number indicates the
amount of soil lost in tons per acre per year. The range of wind erodibility index numbers is 0 to 300.
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