Jason, that piece of land shown in the video sits next to a tillable field. The owner had tried to farm it a few times in the past, but he had given up on it. People told my brother-in-law that he was crazy to even try to pick the rocks from it.
That actually hasn't turned out to be a problem. The fields that he's picked so far are in central Minnesota, and they have remained clean after going through 3 or 4 winters. You can't get much colder winter than what they get over there!