What is soil bulk density?
A. Bulk density is a measure of soil compaction. It is the oven-dried weight of an amount of soil divided by the volume it occupied in the ground. Bulk density is usually expressed in grams per cubic centimeter (g/cm3). In mineral soils (i.e. not organic-based potting media), bulk density is typically between 1 and 2g/cm3. Bulk density is usually measured by taking undisturbed core samples of known volume and drying them in an oven at 100-105 C. The net dried soil weight is then divided by the volume. You can also measure bulk density by digging a small hole and collecting the soil. Then place a plastic bag in the hole and fill it with water. Measure how much water it takes and this will give you the volume. Then dry the soil in an oven set at roughly 100 C (180 F) and again divide the weight by the volume. When soil texture is also known, bulk density provides an accurate assessment of soil compaction level.
