Every time Otwell, Ind., strip-tiller Chris Perkins breaks the 300-bushel barrier, a framed vintage DeKalb seed bag goes up on his office walls, showing the year, hybrid type and yield number. He’s running out of wall space.

Just down the road from the machine shed of Pennville, Ind., strip-tiller Shane Houck, a tan boulder stands halfway between the edge of the cornfield and the county blacktop. Cut into the top of the rock is the inscription, “Houck Homestead Farm 1838.”