Yeah,...........it's Bryce,............If  you have a plain  Ground plane (flat color, no texture) you can try rendering an object mask of it and use an image editor ( PS, PSP, etc.) to add blur to soften the shadows. The IBL function in B6.1 is great on certain object and landscapes however,.......the shadows are by and large going to be hard edged.

"Any club that would have me as a member is probably not worth joining" -Groucho Marx