Iowa State University years ago did some checks of soil temperature in a cleared strip in bean stubble using planter row cleaners.  I don't remember all of the details but there was a dramatic difference in soil temps a few hours after planting using row cleaners vs no row cleaners planting corn into bean stubble. 

As I recall they also did some yield comparisons vs the width of the cleared strip.  Up to a point the corn yield seemed to really benefit from a wider cleared, bare, warmer soil strip.

Jim at Dawn