"most of the topsoil" is relative on this context. In Canada and Scandinavia there is nearly no topsoil left compared to regions which haven't gone through repeated glaciations. However what is there is sufficient to grow food. Yes, I am a geologist.

What about northern Siberia? Is there more topsoil there than at similar latitudes in Canada and Scandinavia?

ADDED. I have a tentative answer to my own question: glaciers probably cannot push topsoil over mountains, which is probably why there is farming in Alberta, Canada, at latitudes where there is no farming in Quebec. (The Rockies take a big zap westward there.) Since there are lots of mountains running east-to-west in western Siberia, there are probably regions rich in topsoil north of those mountains, but not in eastern Siberia, and not in the high latitudes of European Russia.

Unless in the regions north of those west-east mountains, the presence of the mountains caused the glaciers to flow from south to north. hmm.