Page 1
SOIL TEX TURE UNIT
LMott
CODE 1067
QUAN TITY CON TENTS CODE
60 mL Soil Flocculating Reagent 5643PS-H
60 mL *Texture Dispersing Reagent *5644PS-H
1 Soil Texture Stand 1053
3 Test Tubes, Soil Texture, 50 mL, w/caps 0760
2 Pipets, 1 mL, plastic, w/caps 0372
1 A Study of Soil Science Handbook 1530
*WARNING: Reagents marked with a * are considered hazardous substances.
Material Safety Data Sheets (MSDS) are supplied for these reagents. For your
safety, read label and accompanying MSDS before using.
To order individual reagents or test kit components, use the specified code
number.
This test is designed to separate soil into its three basic mineral fractions:
sand, silt, and clay. The amount of time required for the soil particles of
various sizes to settle in the soil separation tubes forms the basis for this
test. From the amount of material collected in each tube it is possible to
determine the approximate percentage of each fraction as represented in
the original soil sample.
The procedure for preparation of the soil sample for testing is described in
the accompanying handbook, A Study Of Soil Science.
The separation tubes should be marked for identification in the following
manner: Mark the first sedimentation tube “A”, the second “B”, and the
third “C”.
PRO CE DURE
1. Place the three Soil Separation Tubes in the rack.
2. Add the soil sample to Soil Separation Tube “A” until it is even with
line 15.
NOTE: Gently tap the bottom of the tube on a firm surface to pack
the soil and eliminate air spaces.
Page 2
3. Use the pipet (0372) to add 1 mL of *Texture Dispersing Reagent
(5644PS) to the sample in Soil Separation Tube “A”. Dilute to line
45 with tap water.
4. Cap and gently shake for two minutes, making sure the soil sample
and water are thoroughly mixed.
The sample is now ready for separation. The separation is accomplished by
allowing a predetermined time for each fraction to settle out of the
solution. Be sure that you continue to gently shake the separation tube up
to the time of the first separation (Step 5).
5. Place Soil Separation Tube “A” in the rack. Allow to stand
undisturbed for exactly 30 seconds.
6. Carefully pour off all the solution into Soil Separation Tube “B”.
Return Tube “A” to the rack. Allow Tube “B” to stand undisturbed for
30 minutes.
7. Carefully pour off the solution from Soil Separation Tube “B” into
Soil Separation Tube “C”. Return Tube “B” to the rack.
8. Add 1 mL of Soil Flocculation Reagent (5643PS) to Soil Separation
Tube “C”. Cap and gently shake for one minute.
9. Place the Soil Separation Tube “C” in the rack and allow to stand
until all the clay in suspension settles. This may require up to 24
hours.
NOTE: Unless there is further use of the clay sample for air drying and study
as described later, it is not necessary to wait for the suspension to settle.
Due to the colloidal nature of clay in solution and its tendency to swell
and form a gel, the portion of clay remaining in Tube “C” is not used to
determine the clay fraction present in the soil. The clay fraction is
calculated by adding the sand and silt fractions and subtracting this total
from the initial volume of soil used for the separation.
EXAMPLE:
Tube “A” Sand 2 Initial Volume 15
+Tube “B” Silt +8 Total “A” & “B” -10
Total “A” & “B” 10 Clay 5
10. Read Soil Separation Tube “A” at top of soil level. To calculate
percentage sand in the soil, divide reading by 15. Multiply by 100.
Record as % sand.
11. Read Soil Separation Tube “B” at top of soil level. To calculate
percentage silt in the soil, divide reading by 15. Multiply by 100.
Record as % silt.
Page 3
12. Calculate volume of clay as shown above. To calculate percent clay in
the soil, divide value by 15. Multiply by 100. Record as % clay.
CAL CU LA TION
EX AM PLE:
Soil Separation Tube “A” reads 2.
Soil Separation Tube “B” reads 8.
Percent Sand = Reading A x 100 = 2 x 100 = 13%
Total Volume 15
Percent Silt = Reading B x 100 = 8 x 100 = 53%
Total Volume 15
Percent Clay = Calculated Volume x 100= 5 x 100 = 33%
Total Volume 15
Since the scientific basis of the test is the particle size and its mass, as
related to its settling time when dispersed in solution, the following table
is included for reference.
Soil Particle
Diameter In mm
Very Course Sand 2.0 – 1.0
Course Sand 1.0 – 0.5
Medium Sand 0.5 – 0.25
Fine Sand 0.25 – 0.10
Very Fine Sand 0.10 – 0.05
Silt 0.05 – 0.002
Clay Less than 0.002
IN TER PRE TA TION
Sandy soil is described as soil material that contains 85% or more sand.
The percentage of silt plus 1.5 times the percentage of clay shall not
exceed 15.
Silt soil is described as soil material that contains 80% or more silt and less
than 12% clay.
Clay soil is described as soil material that contains 40% or more clay, less
than 45% sand and less than 40% silt.
Page 4
To further describe the various graduations possible under each general
soil texture classification mentioned above, additional terms have been
applied. Some examples of these are loamy sand, sandy loam, silty clay
loam, sandy clay or a silty clay.
Once the three textural classes for a soil have been determined it may be
of further interest to place the material from each Soil Separation Tube in
individual piles on a piece of paper. Allow sufficient time for air drying.
Now it is possible to determine the feel of the various textural classes. This
experience will be helpful when the student is in the field.
The following statements give the more obvious characteristics of a
textural class based on its feel when rubbed between the fingers.
Sand is loose and single grained and will fall apart after being squeezed
when dry. When sand is wet it will form a cast that falls apart after being
squeezed.
Sandy loam contains mostly sand, but also some silt and clay. Individual
sand grains can be felt and seen.
Silt loam has a moderate amount of the very find grains of sand, is
fine-textured and contains only a small amount of clay. A dry sample feels
smooth and silky like flour or talcum powder.
Clay loam is a fine-textured soil that after working breaks up into clods or
lumps that are hard to break when dry. A wet cast forms a smooth smear
and is sticky when squeezed.
WA TER SED I MEN TA TION TEST
These tubes may also be used as sedimentation tubes for the study of turbid
waters.
1. Fill tubes to the 50 mL mark with sample water. Cap and place in the
plastic rack. Leave undisturbed until all the solid material has settled.
CALCULATION: Each 0.5 mL of solid material collected is
equivalent to 1% of the total volume.
LaMOTTE COM PANY
Helping Peo ple Solve An a lyt i cal Challenges
PO Box 329 • Chestertown • Mary land • 21620 • USA
800-344-3100 • 410-778-3100 (Out side U.S.A.) • Fax 410-778-6394
Visit us on the web at www.lamotte.com
SM
2/01
Loading...