This will depend on what is under the topsoil.
2-3 inches
This question has no real answer as it depends where you stay and the availability of top soil. How much is a cubic yard of topsoil in Iceland? How much is a cubic yard of topsoil in the Sahara Desert? How much is a cubic yard of topsoil in Washington DC? etc. etc. Check a local newspaper or nursery/ garden centre
Overgrazing does not destroy topsoil so much as it decimates all the vegetation. When sheep graze they tend to snip off the grass lower to the base than cattle. This is sometimes a contributor to overgrazing, which then leaves the land bare, and then the wind and the rain blow away the topsoil. Then the result is that crops don't grow as well, it's a much more complex problem.
(43,560) x (depth of the topsoil in feet) cubic feet
very little
5555 cm
10 cup of letters
1.45lbs per bushel
twice a day then the corn will grow happily .. ~yep , that's right .. ~!
839
40 yds
70 feet.