The ability of soil to absorb and allow water and air to pass through is called

• A. Porosity
• B. Density
• C. Capillarity
• D. Permeability

Answer: (D)

Permeability is the soil’s ability to transmit water and air through its pore spaces. This directly matches the idea of something moving through the soil, not just how much pore space exists. Soils with high permeability, like sand, have connected, larger pores that allow fluids and air to pass quickly. Soils with low permeability, like clay, have tiny, poorly connected pores that slow or block movement. Porosity, by contrast, is about how much empty space is available, not how easily fluids move through it. Capillarity deals with how water can rise in small pores due to capillary action, which is about movement in narrow channels rather than overall flow through the soil. Density describes how compact the soil is, which can influence permeability but isn’t itself the measure of flow through the soil.