WinterDeere
Elite Member
Clay for all but the top few inches, then organic product mixed into top 6'ish inches. Clay gives stable fill, the organic product gives something for grass or groundcover to take root, and provides some drainage.
For that organic product on top I've used something sold locally as Earthmate, essentially composted sewage sludge and old mulch, which has worked well for me. I order it mixed 60%/40% into regular "topsoil", which around here is code for "clay sifted for rocks". Not as acidic as mushroom soil, and doesn't rob as much nitrogen from your plantings as composted mulch alone.
For that organic product on top I've used something sold locally as Earthmate, essentially composted sewage sludge and old mulch, which has worked well for me. I order it mixed 60%/40% into regular "topsoil", which around here is code for "clay sifted for rocks". Not as acidic as mushroom soil, and doesn't rob as much nitrogen from your plantings as composted mulch alone.