We just finished building a frame for our raised garden bed and now I'm trying to figure out what to do for soil. The plan was originally to take the dirt that we're digging up from another project and use that as fill dirt in the bed and then just add a good layer of topsoil. The bed is HUGE, spanning the width of our yard so I was hoping that we wouldn't have to purchase too much to make happy soil. Will doing something like that work or do I need to buy all kinds of additives to play with the nitrogen, alkalinity, etc? It's pretty typical Florida soil in that it's largely sand. Any advice would be *greatly* appreciated.