OK...I apologize. I assume I erred due to semantics.

OP said "most Iowa farms.....".

To me, a farm is the overall body. A field is a portion of a farm. Farms are made up of fields. Could be colloquial though. Here when someone asks "how much do you farm" they are asking about overall acreage, not just the 40/80/160/320 acre field you happen to be standing in.

My apologies for misunderstanding.