Bulk density, one-third bar, is the oven-dry weight of the soil material less than 2 mm in size per unit volume of soil at water tension of -0.33 bar (-33 kPa), expressed in grams per cubic centimeter. Bulk density influences plant growth and engineering applications. It is used to convert measurements from a weight basis to a volume basis. Within a family- level particle-size class, bulk density is an indicator of how well plant roots are able to extend into the soil. Bulk density is used to calculate porosity. Bulk density at 33 kPa is used for soil classification in the required characteristics for andic soil properties and in the criteria for Andic, Aquandic, and Vitrandic subgroups.

Contact: Estella Smith, Geospatial Technology and Applications Center (GTAC), USFS. estella.smith@usda.gov