"A fazenda somos nós."
The sentence is correct and it means "we are the farm". This is not so rare in Portuguese, although not so frequent. This kind of expression is used when you want to highlight that people are important and something would not exist without them.
Try googling for "somos nozes" (not the same expression but a joke on it), and you'll get a lot of results.
Yes, this makes no sense. I kept thinking the structure of the sentence was off, but settled with the farm is ours. First of all-I would have thought that is would not be somos in this situation- it should have been e--but I figured it out and it was till wrong-The farm is us! who knew?