Swathing or combining in soft soil conditions will leave ruts. Some fields will also have ruts from spraying fungicide at flowering. We know that tillage will spread clubroot as well as weed seeds and verticillium, but ruts can create headaches for combining, fall spraying and seeding next spring. Working wet fields can also cause compaction.
Duals on a combine can reduce rut depth. Harrowing can be enough to smooth most ruts. If using tillage to take care of deep ruts, do fields at risk of clubroot last and be strategic with tillage in these fields. Stick to ruts only and leave the rest of the field, if possible.