There are two ways to define this, one definition is based on water content, the other is based on water pressure. This definition includes the capillary fringe. The difinition is difficult for workers to apply during field evaluations. Water Pressure definition. The water has a pressure that is greater than atmospheric pressure.
Free water fills wells and auger holes.
The definition can be applied in the field. It does not include the capillary fringe. Then reduction occurs. Oxidation-reduciton reactions causes gray colors to form in wet soils. These reactions need organic matter, bacteria, and no air to be present in order to work.