FARGO, N.D. — Just about every farmer in Agweek country might have had the chance to pick field rock in their lifetimes.
Kenneth Lepper, a geologist at North Dakota State University in Fargo, notes that much of the Upper Great Plains and Midwest were glaciated in the so-called Quatemary period, 10,000 years to 2.6 million years ago. The most abundant sediment is called “till,” which is fine-grained but contains cobbles and boulders — field rock.
SEBEKA, Minn. — On a field in northeast Otter Tail County, Minn., littered with field stones ranging from pebbles to volleyballs, the RP 1000 moves onward and then upward.
A curious, self-propelled contraption moves ahead at about 3 mph, unearthing rocks in a 20-foot width. Irregular rocks disappear into a cylindrical sieve that takes them to a conveyor and then onto a heavy-duty, high-lift box.
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