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.