One unanswered question.
SPOILERS - so who DID put the ear in the field? If it was either Frank Booth or one of his goons, weren't any of them afraid that eventually it may end up getting discovered and lead the police to them?
shareNo doubt the question will remained unanswered because I don't think there's anything in the film to explicitly and definitively inform us.
My guess is that the ear cutting was performed in the same field in which the ear was found. Cutting it off at the apartment might have resulted in screaming (from various parties) that could alert neighbors to call the police.
I assume the field was remote -- enough -- to allow some affordable distance from any chance of that happening.