Soil bulk density is defined as the ratio of the mass of dry solids to the bulk volume of the soil occupied by those dry solids. Bulk density of the soil is an important site characterization parameter since it changes for a given soil. It varies with structural condition of the soil, particularly that related to packing. The Soil Bulk Density Data Set contains bulk density of the soil based on dry weight at two depths, 0-10 cm and 10-20 cm. Samples were collected at 31 different locations within the FIFE study area during the growing season of 1987. Samples were collected primarily in the northwest quadrant of the study area but at least one sitegrid is located in each of the quadrants of the study area.