I have heard the DOT cracking down on farm trucks and trailers.  Reading the first link, I would say that after reading the definitions and subdivisions, you should be fine with a regular drivers license.

  Reading the second link, I think where they are going to get you is #2 regulation.  It ask if the underlying activity is being deducted as a business expense for tax purposes.  You will probably have to answer yes, if you have the truck in the business name and/or deducting fuel as a business expense.  Then, you have to ask if the GVW of truck and trailer is greater than 10,000 lbs.  My 96 3/4 Dodge has a GVW of 8800 lbs.  It is not going to take much of a trailer to have a GVW of 1200 + lbs. since most car trailers have a GVW of 7000 lbs.  I think they are going to make a determination, based on what you are hauling with the trailer.

  I think I see the angle that you are going with, is the definition of truck and pickup truck.  I think there needs to be some additional subdivisions added to clarify this grey area.  My opinion, for what it is worth.  If you are using your truck and trailer for your farm business use and are not hauling for hire, you should not be licensed as a commercial vehicle.  You would need to carry the proper tonnage, of the combined weight of the truck and trailer, on the pickup truck.