The farm im hunting is open land. Are ground blind a good thing or not.

Better than sitting out in the open for sure!      Put it out and let the deer get used to it being there.  Might want to shoot out of it a few times to get a feel for keeping your bow clear of hitting the blind.

Yes a ground blind will be good if you can back it up to a fence or something on the fringes.You can also dig a pit if your allowed and get your self about half way in the ground  with a little cover on the top half, works good also.