Beth, When you use straight Pro Mix BX by its self and add the fertilizer or "nutrients" to the water this is essentially "soil-less" growing or hydroponics so to speak. This is because the Promix is essentially an inert (no nutrient value) medium similar to straight perlite. When you add amendments to the Promix like compost (worm castings, cow manure, mushroom, lobster, chicken, yard), meals (bone, blood, feather, kelp, alfalfa, crab etc.) gaunos (bat, sea bird), minerals (azomite, soft rock phosphates, sul po mag, oyster shells, lime greensand) you are now growing in a soil mix. If all the amendments are properly adjusted you can water with plain old tap water and not add anything to the H2O as far as macro nutrients (NPK) go. So to recap straight Promix Bx is soil-less and Promix Bx with all the proper amendments is soil growing (examples: Roots Organic, Fox Farm OF, Coast of Main, Vital Earth etc). This is a broad definition of both types of growing media and each has many different approaches and nutrient recipes. I would also not recommend adding lime to the BX, it is already in there. I will offer one more piece of advice and with it I will be opening up a huge debate but here we go. If you plan on using bottled nutrients don't be fooled by these product lines that offer 4-10 different bottles of crap for your grow cycle. There are many great economically superior products that are over looked because they aren't flashy and over marketed. But as everyone will agree (LOL) organic TLO soil growing is superior in every aspect of fruit production. My $.02 worth.
