ABSTRACT
The complexity of the interactions of soil air with the soil environment and with plant roots is such that although there are many indicators of soil aeration status, each reflecting particular aspects of it, none of them adequately describes the whole of the phenomenon. Determining the air-filled porosity is the oldest and the simplest method of assessing soil aeration status. Air permeability appears as the constant included in the Darcy equation for the mass flow of gases in porous solids. In air permeability measurements, high pressure gradients must be avoided in order to eliminate turbulent gas flow and thus to preserve the validity of the Darcy equation. The methods of incubation besides differentiation in the size and shape of the soil containing vessels can be divided into three groups with respect to the methods of air exchange: no air flow; continuous air flow; and intermittent air flow.
