I have seen turkeys spook from blinds in the open and in the cover. If possible set up blind well in advance and put natural cover around it, branches, downed trees, or any type of brush. If this field has round bales in it consider using them to your advantage.
If you have to set up the morning of, get their early, put some natural brush around the blind and hope for a calm day, wind seems to cause the blind to move and birds spook if they havent seen it before.