Below are pictures of fields that have always been tilled in the past. There is erosion even before the tillage has been started this spring. We don't see anything like this on the No-Tilled fields.
We assume there are several reasons why this occurs. The tilled ground has deep compaction from being worked while wet during the wet 1990s. Todays larger and heavier equipment is causing compaction much deeper than it used to. There has been severe erosion this same time period and there is a lot less topsoil on the sidehills so the water runs off the clay much easier. On some sidehills the subsoil has been exposed in many spots. The rest of the sidehill is so badly eroded and because of extensive tillage there is very little organic matter left.