Thanks for the save game, i loaded it up.
You definitly dont have any tile yields anywhere. It isn't that there isn't fertile land, there is plently of it. There is a bug keeping it from giving yields.
I suspect that you had some modified xml that is causing this (your tile yields aren't the same as my tile yields). XML is stored in the save file so I can definitely see the issue. We are working on a new installer than will overwrite all your local xml data and resolve this, if that is the issue.