every time a planter gage wheel rolls over a clod or stalk your seed depth is going to change.  you cant see it on top but the seed depth changes by 1/2 the height of the clod, cob or rootball. 

this sometimes causes us to have a deeper seed depth setting than really necessary and usually more row unit down pressure than really necessary, possibly causing more sidewall compaction than necessary, etc...

finger-type row cleaners, located back as close to the gage wheels as possible, with wheels set offset, with depth properly set to move clods and rootballs, not soil, will give the planter gage wheels a more consistent surface to gage seed depth from. 

more disc-like row cleaners were called "furrow openers" a few years ago and they will provide a level surface but often leaving just what their name implies - a furrow. the more closed the outer 2" or so of a row cleaner wheel the more apt it is to move soil rather than act like a rake for clearing just clods and rootballs.

the end result of having a finger type row cleaner on a planter row unit in conditions where the soil surface is not perfectly smooth is more uniform seed depth and therefore more uniform emergence and also more consistent spacing to reduced row unit bounce without excessive downforce. seed slot closure is often better with a more consistent and accurate seed depth - no need to add a fudge factor to avoid seed laying on top of the ground.

the return on the investment in row cleaners can  be very quick.

jim at dawn