He runs the sweeps 4 to 6 inches deep, the same depth as the fall passes with the chisel points. I travel about six miles per hour when I m chiseling. Higher speed makes the sweeps harder to keep in the ground and harder to drive straight. Plus it s harder on equipment. He comes back to the fallow fields with the tool when weeds rebound in June, then again in late August or early September.
Some seasons take as many as four passes.
Smith knocks down the weeds while keeping all the residue he can on the surface. He raises the sweeps about an inch each time to bring the subsoil moisture zone closer to the surface in anticipation of fall wheat planting. The implement is a ground-driven model with a round rod that spins just beneath the soil surface. Smith feels the square rod used in the 1930s did a better job of weeding. Maintenance of drive sprockets and chains is important, he says, as is keeping speed below 4 mph to prolong tool life and avoid downtime.