I only use tilled up old compost from last year with about a double handfull of worm castings at the bottom of the hole. I spread some more castings on top when the leaves start forming.

My most recent mix is Ace Hardware organic potting mix and Ace Hardware organic very small wood chips - mixed half and half. I mix in about 1/8 steer manure and as much as I feel I can afford of worm castings (my motivation for starting a composter). I also top dress all existing pots with worm castings and mulch on top of that with the Ace compost. We are very hot and dry here in the summer, so conserving as much moisture as possible is crucial. I get bagged compost and manure mainly because I injured my shoulder a couple of years ago and it's easier to drag the stuff where I need it than to shovel it into the wheelbarrow and haul...

BettyN