Growing Media Physical Properties: 21 Feb 2019 Version Download 613 File Size 0.00 KB File Count 1 Create Date February 21, 2019 Last Updated February 21, 2019 Download Description Air filled porosity (AFP), water holding capacity (WHC), bulk density, shrinkage, wettability and water retention efficiency (WRE) are all physical properties of growing media that influence plant growth and ultimately plant health.