How to make shadows appear on a created background from a part?

Hey guys, I have created a floor and sky by making seperate parts and putting the desired material on them.  The issue is (as you can see in the uploaded pick) i cant get the shadows of the star pickets and flags to appear on my created ground.  I tried playing around with the lighting and looking through the grounds material propperties but i couldnt see anything to enable the shadow. 

ps running solidworks 2013

Thanks! 

SolidworksPhotoview 360