Disclaimer: This post was originally posted by Hero Member, Donald1800. This user is located in Fontana, CA Zone 8. This was originally posted on April 29, 2008.
The primary secret of the EBs success is the wicking of water from the bottom to the top, as opposed to the typical garden method of watering from the top to the bottom. As such, the primary functional criteria and requirement of the potting mix is the wicking capability. Therefore, the two main ingredients on the contents list should list as the first Sphagnum Peat and/or Coir - usually 70-80%, with the balance some combination of Vermiculite, Perlite and even Carbon (with the emphasis on the Vermiculite). Mix components which do not contribute to this wicking action are anything Partially Composted..., Forest Biproducts, Sawdust, Bark, Screened Topsoil, etc. Currently most Soils and Mixes available today have listed these very ingredients as the first few, which in my opinion are not suitable for THIS application.
Note: The first ingredient your mix lists is " Forest Humus", which I have serious doubt is an accurate description. Forests typically do NOT have Humus in sufficient quantity to harvest as a main ingredient in a commercial mix. It is usually listed more accurately as Partially Composted Forest Biproducts which, besides NOT acting as a wick, is actually a nitrogen thief in its attempt to finish its composting.
That is why I have taken the unusual step, in both time and effort, to make my own mix for my 34+ boxes. I just could not get what is needed within a reasonable shipping distance, and the EB mix cost with shipping is unrealistic.
I hope this helps clarify what was missed in all of the other Mix vs. Soil posts.
Donald1800