Porosity and Permeability

The spaces where the air and water reside are called voids or pores, and the amount of space a soil has for storing air or water is its porosity. If the pores are not connected well, a soil can store water but doesn´t transmit it well - that is, it can be porous but not permeable. A soil with pore spaces that are well-connected, on the other hand, is porous AND permeable. It can store water, but it can also transmit the water. A soil that is porous and permeable, like a sandy loam, is much better for growing plants than a very porous soil that isn´t permeable - like clay, which has up to 50% porosity but doesn´t transmit the water well.

Soil Defined

"Soil" means different things to different people. Soil scientists use it to mean unconsolidated granular material that has enough organic matter in it to support plant growth. Engineers use it to mean earth material that can be bulldozed away, without having to use dynamite.

Geologists use the term either way.