We heavy harrow every acre in spring. Maybe it's because its been so wet and cold. Sometimes we don't get all acres harrowed in fall due to lack of man power. Also if I want to spray a canola stubble for thistles I won't harrow it in fall. We're usually doing it two ways in spring. Harrow early if nothing growing, hopefully get something to grow then spray. Or spray then harrow next day, seed same or next day after that. A lot of factors I guess. Some stuff we harrowed this year seemed to break too much straw apart and caused problem with banders, but there's ways around that I guess. We don't own any other kind of harrow.