That is the benefit of using the "poo ball" type of fertilizer. A little fertilizer gets released every time you water.Which is basically impossible as we all know, to give the trees in bonsai soil the same level of nutrients would mean daily fertilzing, which I'm definitely to poor for that crap
I personally like to put conifers into inorganic substrate as its easier to trasiton into a bonsai pot later on, and it's harder to replace long intrenodes with short ones lol but most of my deciduous in training LOVE them some organics and beef up much quicker.
Aaron