What kind of soil did you use?
Mel’s mix in 1 4x4 and the other one a combo of peat moss, compost and vermiculite.
Lots of research is ongoing into what makes it so darn good. Some main points seem to be adding real charcoal and small pieces of terra cotta to the soil along with kitchen wastes, etc...
I'm already composting, I'll be adding the charcoal and terra cotta as I go along.
Apparently it give more nooks and cranies for micro-organisms.
/johnny