Why are fields sometimes plowed only along the perimeter?

Question

I notice then when driving along highways that are next to fields. The perimeter of the field will be plowed around the perimeter, near the fence, but not necessarily right up to it (there might be several feet of unploughed field next to the fence).

Answer 1

Well they won't plow too near the fence for fear of damaging it. I assume that you're talking about fields "at rest" for a season. Because the field is not being tended, plowing the field around the perimeter helps keep weeds and burrowing animals from encroaching.

Answer 2

I always thought it was to break up compaction.