Answer: False. Deep tillage can shatter compaction layers created by wheel traffic or tillage, “but it doesn’t bring the soil back to normal,” Reeder says. And in the Midwest, “it has not been proven to increase yield consistently or for long periods of time,” DeJong-Hughes says.

“If we have a lot of compaction near the surface, subsoiling can temporarily alleviate it,” Duiker says. But it also increases the risk of future compaction, he says, setting up a damaging cycle of tillage and re-compaction that destroys the soil structure.

Subsoiling may be justified if you are changing from your old conventional tillage program to controlled traffic, Reeder says. In Ohio research from 1992 to 2002, subsoiling after compaction with a 20-ton/axle load raised corn yields about 3% and soybean yields about 10% compared to chisel plowing – provided there was no additional compaction.

If you do till deeply, DeJong-Hughes says, first determine where the compaction zone is and run the ripper about an inch under the bottom of the compacted layer. Work the soil only when dry – but not too dry. In fall 2011, she notes, soil was so hard and dry in southern Minnesota that tillage brought up huge soil clods. “Soil should fracture and crumble down to the depth of the shanks. Use the most non-invasive, straight shanks.”