Modesto Junior College
Agriculture and Environmental
Sciences
Name _________________
Date _________
SOILS - NR 200
LAB #5
BULK DENSITY DETERMINATION
Procedure:
1. Weigh a clean, dry 100ml. graduated cylinder, record its weight and fill it to the 100ml. mark (equals
100cc.) with one of your assigned (oven dried) soils that has been ground to a fine consistency with
the mortar and pestle remove any rocks and debris. Allow the cylinder to drop freely 5 times through
a distance of ONE INCH onto a book or other soft, flat surface. CYLINDERS ARE FRAGILE:
DROP WITH CARE!
2. Add soil to fill the cylinder again to the 100ml. mark and allow it to drop onto a soft flat surface 3
times through a distance of ONE INCH. Again add soil to refill to the 100mL mark but do NOT
drop.
3. Weigh the cylinder now packed with soil to the 100ml. mark. Record the weight and make the
necessary calculations.
4. Everyone must complete their soil and someone else’s sample. Record your findings.
1
Soil Type or Number
Example
Weight of
Cylinder
Plus Soil in
Grams
Weight of
Empty
Cylinder
158
÷
2
=
3
Weight of
Soil in
Grams (1)
Volume of
Soil in cc.
(ml.) (2)
Bulk
Density in
gms/cc (3)
122
100
1.22
36
Your Soil
100
100
A
Note 1 cc = 1ml
-
B
=
C
Bulk Density (3) = (1)Weight of soil in grams
(2)Volume of soil in cc. (equals ml.)
5. Place a small glass rod upright in the center of a 250ml. beaker and pour the soil from the
cylinder around the rod. Level the surface and start the porosity experiment.
1
POROSITY DETERMINATION
Procedure:
*** Read the bold items at the bottom of this page first. ***
1. Fill a 100ml. graduated cylinder to the 100ml. mark with tap water. Pour the water SLOWLY
onto the soil in the beaker with a glass rod. Stop adding water when it stands at the same level as
the soil surface. Do NOT stir the soil or shake the beaker.
2. Determine the amount of water used to exactly fill the pore space in the 100cc. (ml.) volume of
soil by subtracting the reading on the side of the graduated cylinder from the original volume.
3. Record your results and make the necessary calculations.
Soil Type or
Number
Volume of
Water added
to Pore Space
in cc.
Volume of
Soil in cc.
(ml.)
Percent Pore
Space I
Percent Pore Space II* by
calculation: % =
LOOK AT STEPS BELOW
100 - ( Bulk Density x 100)
Particle Density
Example
53
100
53%
53.96%
Your Soil
Percent Pore Space I = Volume of pore space (water used) x 100
Volume of Soil
Percent Pore Space II = Bulk Density x 100 = Y
Y ÷ Particle Density = X
100 – X = Percent Pore Space II
* In order to calculate % pore space II, it is first necessary to determine both
bulk and particle densities and to apply these figures to the appropriate
equation.
2
PARTICLE DENSITY DETERMINATION
Definition: The particle density is the weight of a known volume of soil solids. The pore
space is not considered. This measurement gives an indication of the density of the parent
material.
Procedure:
1. Place 50ml. of tap water in a 100ml. graduated cylinder. Carefully weigh a 50-gram sample of dry
soil and pour it into the water.
2. Cover the mouth of the graduated cylinder with the palm of the hand and gently rock it back and forth
to mix the soil and water thoroughly.
3. Water level prior to washing down the sides = ________ after washing =
Second Soil Sample = _________
Dif._________
______
_________
4. Rinse the sides of the cylinder with 10 ml of water. Let the mixture stand for 5 minutes. Record
numbers above. Now determine the total water used.
Total water used
= _______ _______ Level after 5 minutes
(50 + water used to rinse)
Your Soil 2nd. Soil
5. Fill in the blanks below and follow the equation for particle density.
_______
Your Soil
1÷2=3
1
Soil Type or
Number
Example
Your Soil
Weight of
Soil in Grams
50
÷
Volume of
Water and
Soil in cc.
(ml.)
2
Total Volume
of water used
in cc. (ml.)
79
Portion of
volume
occupied by
soil in cc.
60
=
3
Particle
Density in
grams/cc.
19
50
50
A
-
B
Particle Density =
=
C
Weight of soil used_(50) ___
cc.(ml) occupied by soil particles
3
2.63
_______
2nd. soil
Now go back to the porosity determination II and complete those calculations.
Name
Physical Properties of Soil
Soil # Bulk Density
Porosity
I
II
4
Particle
Density
Name:
Date:
Bulk Density and Porosity Questions:
1. From your results:
a. How does bulk density vary with the amount of clay in the soil?
b. How does the percent total pore space vary with the percentage of clay in the soil?
2. Do the bulk densities that you found correspond to what you would expect from the
textures of the soils? If not what could be the cause of the discrepancies?
3. Do the values you found for the percent pore space correspond to what you would expect
from those textures? If not what could have caused those discrepancies?
4. Would you expect the soil with the greatest amount of pore space to have the most rapid air and water
movement? Explain (consider the size of the pore space)
5. Discuss how total pore space and individual pore size distribution characteristics are
affected by the soil texture.
6. Explain the difference between permeability and pore space and what influences each?
7. Using the information from the entire class did we find some consistencies with the
numbers ie in terms of texture……..please explain your findings.
5