"Rock picker"
Very cool. My maternal grandfather would have been awestruck to be able to use a piece of equipment like this in his cornfield (instead he had my aunts and uncles fan out through the field each spring to "pick potatoes.")
When I was growing up I never quite figured out why every year rocks would emerge at the surface of the fields. It wasn't until as a an adult when Michael Waters' Principles of Geoarchaeology that I finally understood how the dramatic freeze-thaw cycles of the Upper Midwest result in cryoturbation and "granular convection."
If you visit any old farm in Minnesota and Wisconsin and walk the fields, you will almost certainly see a pile of rocks off at the side - often under shade trees - where generations of a family have picked rocks and tossed them away from the tilled areas.
