martin - 7/7/2016 13:13
I think you missed Nekfarmer's point. It's not that terraces make topsoil. Rather, he feels they didn't have terraces to protect and keep the topsoil on site.
I'm not sure I agree with him, but then again, I don't live in Kansas.
Reading history, you read about the dust bowl days of the 1930's. I have to wonder how much topsoil was lost from Kansas in those days from wind erosion. Terraces would not have helped with that at all.