Bulk density is a property of particulate materials, especially used in reference to soil. It is the mass of many particles of the material divided by the volume they occupy. The volume weight includes particle volume as well as the porosity. [1]
Bulk density is not an intrinsic property of a material; it can change depending on how the material is handled. For example, grain poured in cylinder will have a particular bulk density; if the cylinder is disturbed, the grain particles will move and settle closer together, resulting in a higher bulk density. For this reason, the bulk density of powders is usually reported both as "freely settled" and "tapped" density (where the tapped density refers to the bulk density of the powder after a specified compaction process, usually involving vibration of the container.)
Soil
The bulk density of soil depends greatly on the mineral make up of soil and the degree of compaction. The density of quartz is around 2.65g/cm³ but the bulk density of a mineral soil is normally about half that density.
Most soils have a bulk density between 1.0 and 1.6g/cm³ but organic soil and some friable clay may have a bulk density well below 1g/cm³
Core samples are taken by driving a metal corer into the soil at the desired depth and horizon. The samples are then oven dried and weighed.
Bulk density = mass of oven dry soil*volume-1
The bulk density of soil is inversely related to the porosity of the same soil. The more pore space in a soil the lower the value for bulk density.
See also
Notes
- ^ Page 50 in Buckman, Harry O. & Brady, Nyle C. (1960), The Nature and Property of Soils - A College Text of Edaphology (6th ed.), New York: MacMillan Publishers, New York, NY
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