Home

Mechanical Analysis

Bulk Density (Bd) Activity

Materials needed: Scale, beakers, mortar and pestle , 2 mm sieve or screen,  2 graduated cylinders, calculator

1. Following the field sampling, bagging, and transferring into a container, air-dry overnight at room temperature or 15-35 ^oC in an oven. Let it dry for at least 24 hours. Spread the sample in a plastic or paper tray to promote drying. Check to see if the soil is dry. 

2.  Prepare 200 ml of the soil sample. You need to break up any clumps in the soil by using the mortar and pestle. Remove any organic matter. Do not remove the larger sediment.

3. Place the 200 ml of soil in a pre-weighed or tared beaker.

4. Find the mass of the 200ml of dry soil.

5. Calculate Bd using the following formula:   

      Bd_u = mass of  soil sample (g) / volume of  soil  sample (ml)

6. Filter soil sample for coarse particles > 2  mm , using a 2 mm sieve or screen.

7. Weigh the resulting coarse fraction.

8. Correct volume measurement through the water displacement of the coarse fraction in a separate, 100 ml graduated cylinder. Pour the coarse fraction into the 100 ml graduated cylinder. Measure out 50 ml of water and add this amount to the graduated cylinder containing the coarse fraction. Calculate the volume of the coarse fraction by finding the difference.

9 Calculate Bd as follows:

  Bd_c = mass of the soil sample - mass of the coarse fraction (g) / volume of the soil sample- volume of coarse fraction (ml)

10. Rinse all glassware and place on drying surface.

References: Salvatore Engel Di-Mauro, July 2001, Selected laboratory procedures for investigating general soil characteristics and acidification processes, Manuscript