I remember Gary Cruff (the production adjustment specialist in the ND state office) calling in in the early 80's to be sure management knew what they were doing in changing cropland definitions around pothole areas. We had revised the handbook and in the process had changed the language and the regulations.
The answer to Gary was that the change was intended, though in my memory the assistant deputy administrator who made the call was from Texas which has no potholes and probably did not understand the issues. The potholes represent areas where blocks of ice from the retreating glacier sat, so the glacial debris settled around the ice, which when it melted then created a low area or pothole. Depending on seasonal precipitation, the pothole might fill with water, or might dry around the margins. There are also long-term wet and dry trends--over the course of several dry years the farmer might be able to crop the margins, if not the entire pothole. The question then became: were the marginal areas "cropland" or not; was the land regularly cropped with only occasional and intermittent flooding or was it not possible to crop it in "normal" years? Under the program, land that was cropland could be designated as set-aside/ACR, land that wasn't cropland couldn't, so the farmers wanted as much of the pothole margin to be considered cropland as possible so they could call it set-aside. The assistant deputy administrator took the approach that the program needed to reduce production when it compensated farmers for set-aside, and if the margins were not regularly cropped the farmers were getting a freebie. He was concerned about program integrity and, as a Republican, taxpayer money.
The issue is very sensitive to what management in the 1980's used to call "the duckies", the conservationists. The pothole areas are important for wildlife, particularly for waterfowl and migratory birds. The conservationists could care less back then about "program integrity"; they wanted the potholes protected--call them "cropland" and designate them as set-aside. So, as I recall it, both the conservationists and the farmers were on the same side of that issue at the time. That seems unlikely, so maybe my memory is totally wrong.
Anyway, Sen. Hoeven is giving NRCS flak about its enforcement of conservation compliance. The press release doesn't say so, but IMHO it's potholes again. (Hat tip: Farm Policy) BTW, Sen. Hoeven could use some help on his website--there seems to be some disconnect there. Maybe as much disconnect as my memory and potholes.