No rocks on the bottom, it has been found to be a practice that contributes to poor plant health and harbors snails, slugs, bugs...BT is a better choice to help deter gnats and such. I just use old screening to place over the drain holes. You said a large container, how big? How deep? extra depth would help with keeping the roots from standing too long in moisture, but let me see, North Texas, zone 6 would indicate you are in the region of Dalhart, Perryton, Stratford...up where moisture isn't a problem. Hmmm, most bagged potting soil is a neutral ph, that close to the caprock caliche and limestone, you probably still have a fairly neutral ph, maybe 7.0. I would imagine you would take the ph after you mix the soils, but they won't be a stable ph for some time - especially since you used a form of baking soda that lowers ph. You will need to wash your concoction on out of what you treated it with and allow to dry somewhat.
