Key Terms
Total porosity refers to the total volume of pore space in a substrate and is expressed as a percentage of the total substrate volume. Recommended total porosity values range from 50 to 85%.
Air space refers to the fraction of air-filled large pores from which water drains following irrigation. Air space values are also expressed as a percentage of the total substrate volume, and recommended values range from 10 to 30%.
Container capacity is the maximum volume of water that a substrate can retain following irrigation and drainage and is a measure of the water reservoir of the container. Container capacity is expressed as the percent of water retained relative to the substrate volume.
- Recommended container capacity values range from 45 to 65%. The water in a substrate can also be classified as “available” or “unavailable.” Available water is the fraction of the water that can be absorbed by roots. Unavailable water (hygroscopic water) is the fraction of water that is held tightly to particles and is unavailable to roots.
- Recommended physical characteristic values for nursery container substrates
after irrigation and drainage are listed here in percent volume. Total Porosity: 50 to 85%;
Air Space: 10 to 30%; Container Capacity: 45 to 65%; Available Water content:
25 to 35%; Unavailable Water content: 25 to 35%; and Bulk Density 0.19-0.70
g/cc.
View related article:
"Container Substrate Physical Properties";
The Woody Ornamentalist. Vol. 20, No. 1 (1995)
