Hi Tania,
I guess my challenge is a bit more difficult than "normal" container growing, as my 'Tainers need to wick up moisture from a water reservoir to work properly. So adding manure, for example, would likely break the capillary wicking properties that the SWC 'Tainer needs.
So while I am limited to a soiless potting mix due to the physics of the wicking action, I still would like to come up with an additive blend of additional elements to more closely replicate the taste of good ole in-ground tomatoes. Dice has some interesting ideas that I may experiment with. The 'Tainer environment is a pretty uniform "clinical" platform to conduct "A/B" comparisons, as Kat suggested.
Ray