are you saying CRP land that is coming out?  or are you saying CRP in existing contracts?

My understanding is that once CRP land is established, it cannot receive manure.   I would imagine that once the contract is expired and the land is released, and going back into crop production, then you can apply manure.  However, while it is in CRP, you cannot apply manure. 

At least, that is what I understand *here*.