Being in the North Carolina Piedmont, My land is red clay, just about the best planting medium for plants that you fertilize, then submerge in a pond*. When I dug my ponds, I made a big pile of soil at the back of my lot that I have used for 25 years to pot lilies, etc. Of course, over the years, as I reduced my lily operation and began filling in unused ponds and converting them for growing more tomatoes, I had to purchase topsoil to fill them in so I would have better tomato soil than the red clay was. I still have a pile of clay that should last me as long as I expect to be messing with potting lilies.
*As I have said many times over the years, encasing your fertilizer in a "ball" or clump of clay in the bottom of a pot in which you plant a lily or lotus and then submerge in to a pond allows the plant to access the fertilizer without it being released into the water column, which generally would result in an algea bloom. The fertilizer is sealed inside the clay, which forms a bond at the molecular level with the nutrients, that are still available to the plant.