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PART ONE: Bulk Density Sampling
Note: You will be sharing your bulk density, porosity, and field texture results with the rest
of the class. Please put your results on the board when you have completed the
calculations. These values are needed for some of the questions at the end of the lab.
I. Sampling.
Choose sampling sites from several locations (at least four per lab group) and hypothesize about the
differences in bulk density you expect to find and WHY. Record descriptions of the sampling locations
in the data table. Determine the texture of your samples, using the feel method. (Don't use your bulk
density samples for this! Collect a separate sample of each soil for this!) An accurate determination of
bulk density starts with proper sampling to ensure that the collected sample represents the soil's
natural condition. Follow the diagrams on these links to use the bulk density sampler.
Steps to Using the Bulk Density Sampler :
Step One :
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Step Two:
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Step Three: Step Four:
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II. Laboratory Analysis
1.Dry the soil sample to a constant weight (24 hours in a hot-air oven at 105 degrees C ).
2. Weigh the sample plus beaker. Record as "oven-dry soil + container" on data sheet.
3. Transfer soil into another container while you clean, thoroughly dry and weigh the beaker.
Record as "weight of drying container". (Each beaker has a slightly different weight, so be sure to
weigh each empty beaker). Return soil to beaker. SAVE THESE SAMPLES!
NOTE: You will need these beaker weights for the organic matter lab, so be sure to re-label your
beakers and return samples to the proper beakers after cleaning and weighing thebeakers.
4. Subtract weight of beaker from weight of beaker plus soil to get "weight of oven-dry soil".
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5. The volume of the sampling cylinder is 137.4 cubic centimeters. Calculate the bulk density
and porosity of the sample, based on the formulas presented in the Background section..
PART TWO: Particle Density
Particle density (as well as bulk density) of a sand can be easily approximated in the
laboratory by the following procedure.
1. Weigh 50 g of dry sand and use a funnel to quantitatively transfer
to a 100-mL graduated cylinder.
2. Carefully tap the cylinder 4 times to settle the sand. Read the
volume and record on your data sheet. Calculate the bulk
density.
3. Transfer the sand to a container and save.
4. Add approximately 60 mL of water to the 100 mL graduated
cylinder. Record the exact water volume. (Assume the density of
water is 1 g c/m3).
5. Transfer the 50 g of sand from step 3 back into the cylinder. Stir
to remove the trapped air.
6. Read and record the volume. Note the difference in the volume
and that in step 4, this is the volume of the sand particles.
7. Calculate the particle density by dividing the weight of the sand
(50 g) by the volume of the sand particles.
8. Calculate the pore space (% porosity).
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