Air Filled Porosity 
The percentage of pore spaces within a soil that are filled with air. A soil which has a low percentage of air-filled porosity will typically be poorly drained with poor root development. It is also called Air Porosity.
Air Filled Porosity
The percentage of pore spaces within a soil that are filled with air. A soil which has a low percentage of air-filled porosity will typically be poorly drained with poor root development. It is also called Air Porosity.