Here in MN unless its written in the contract it's illegal.  We had that happen a little different way to us where we were renting a piece and the guy sold it to close on Dec 15th.  After we were done the current landlord went in and baled every acre.  This is on some very steep ground that IMO shouldn't have been baled.  We tried renting the farm back from the guy who bought it but we were unsuccessful however he was not aware that the previous owner took the stalks off and wasn't very happy about it.  

In my mind the stalks belong to the land unless stated in the contract or another way to look at it is if the stalks were there when you rented it they should be there when the lease is over.  Just my opinion.