If your last name would be "Stapelfeldt", it would be more probable, because there are only about 800 people in Germany with that name. But don`t ask me, what it means ("stapeln" = "to stack, to pile up"; "Feld" = "field"), maybe farmers again?
There is a small village near Hamburg (not so far from my home) called Stapelfeld. That is where we came from, being an old farmers dynasty. It is not clear if the name has perhaps some connection to the old work of turfcutting (turffields are cut in layers, piled over one another).