...well, I'd suggest a soilless medium such as Promix, or Sunshine mix...and possibly the General Hydroponics 3 part (micro, grow, bloom). ...a soilless medium has the perfect texture for water retention and aeration (vermiculite, perlite, petemoss) and it will look just like potting soils sold in bags and such, but it is not soil...soil isn't soil without humus, or the organic component formed by the decomposition of leaves and other plant material by soil microorganisms. ...in your case, you wouldn't want any life in your soil, since your going to add synthetic fertilizers (or salts), you don't want soil at all...the salts would only dehydrate the microbes, and they die...what your attempting is a passive hydroponic technique with a soilless medium. ...your going to have the salts to build up quickly in a system like this so your going to need to feed very, very little and flush often. The salts are acidic on a pH scale and the medium buffers the salts really, really well... which in turn makes your medium too acidic for the plants to absorb the fertilizers. ...I do not condone salts in soil, it's counter productive...IMO, it's either full blown organics, or full blown hydroponics, I would never mixed the two...just my $.02
The Passive System: This is almost identical to growing a plant in a container of soil. The difference is that instead of soil, you would use a soilless mix. Soilless mixes can be a variety of substances including rockwool, peat moss, coconut coir, perlite, vermiculite, tree bark, etc.