I think you are going beyond the mileage allowed by MAP-21, so some of the farmer exceptions might be out the window.
http://www.gpo.gov/fdsys/pkg/FR-2012-10-01/pdf/2012-24106.pdf
It all depends on your farming operation. If you make the slightest gain financially or in other ways with the farm, your operation on the road could be considered to be in commerce, hence requiring some of the same equipment and paperwork that the big trucks run. In that case a combined GVWR rating over 10,000 pounds will put you in the Federal Regulations. Trust me it is all up to the person that stops you on the road. If they think you make money farming and are hauling hay to feed the cattle that you sale and make money with, then they will more than likely say you are in interstate commerce. The following link will get you into the Federal REGS.
http://www.fmcsa.dot.gov/regulations/title49/section/390.3
Here is the Feds definition of a commercial motor vehicle of which the rules apply to if in commerce.
Commercial motor vehicle means any self-propelled or towed motor vehicle used on a highway in interstate commerce to transport passengers or property when the vehicle—
(1) Has a gross vehicle weight rating or gross combination weight rating, or gross vehicle weight or gross combination weight, of 4,536 kg (10,001 pounds) or more, whichever is greater; or
(2) Is designed or used to transport more than 8 passengers (including the driver) for compensation; or
(3) Is designed or used to transport more than 15 passengers, including the driver, and is not used to transport passengers for compensation; or
(4) Is used in transporting material found by the Secretary of Transportation to be hazardous under 49 U.S.C. 5103 and transported in a quantity requiring placarding under regulations prescribed by the Secretary under 49 CFR, subtitle B, chapter I, subchapter C.
Also here is their definition of interstate commerce:
Interstate commerce means trade, traffic, or transportation in the United States—
(1) Between a place in a State and a place outside of such State (including a place outside of the United States);
(2) Between two places in a State through another State or a place outside of the United States; or
(3) Between two places in a State as part of trade, traffic, or transportation originating or terminating outside the State or the United States.
More of the way they see it:
Interstate Commerce is trade, traffic, or transportation involving the crossing of a State boundary. Either the vehicle, its passengers, or cargo must cross a State boundary, or there must be the intent to cross a State boundary to be considered an interstate carrier. Intrastate commerce is trade, traffic, or transportation within a single State.Interstate commerce is determined by the essential character of the movement, manifested by the shipper's fixed and persistent intent at the time of shipment, and is ascertained from all of the facts and circumstances surrounding the transportation. When the intent of the transportation being performed is interstate in nature, even when the route is within the boundaries of a single state, the driver and the CMV are subject to Federal Motor Carrier Safety Regulations. - See more at:
http://www.fmcsa.dot.gov/medical/dr...river-exemption-programs#sthash.ZAZGuxSF.dpuf
What are the GVWR Ratings on the truck and the trailer. Usually a combined rating or gross weight over 26,000 LBS will require a CDL unless you meet the farm exemption which probably has the mileage limitation of 100 or 150 miles. Over that then probably you are in the CDL game.
I know you are curious about their rules on CDL'S. HERE:
Pursuant to Federal standards, States issue CDLs and CLPs to drivers according to the following license classifications:
Class A: Any combination of vehicles which has a gross combination weight rating or gross combination weight of 11,794 kilograms or more (26,001 pounds or more) whichever is greater, inclusive of a towed unit(s) with a gross vehicle weight rating or gross vehicle weight of more than 4,536 kilograms (10,000 pounds) whichever is greater.
Class B: Any single vehicle which has a gross vehicle weight rating or gross vehicle weight of 11,794 or more kilograms (26,001 pounds or more), or any such vehicle towing a vehicle with a gross vehicle weight rating or gross vehicle weight that does not exceed 4,536 kilograms (10,000 pounds).
Class C: Any single vehicle, or combination of vehicles, that does not meet the definition of Class A or Class B, but is either designed to transport 16 or more passengers, including the driver, or is transporting material that has been designated as hazardous under 49 U.S.C. 5103 and is required to be placarded under subpart F of 49 CFR Part 172 or is transporting any quantity of a material listed as a select agent or toxin in 42 CFR Part 73.
- See more at:
http://www.fmcsa.dot.gov/registration/commercial-drivers-license/drivers#sthash.eQ4BD9az.dpuf
If your truck and trailer weigh over 26,000 pounds then usually fuel permits are required and in some cases apportioned tags unless you run a farm plate on the truck and other states honor that. Also how much tag (registered) weight does the truck have. In most cases you want to make sure the tag covers the truck, trailer and load.
Hope that stuff does not scare you, but one can get in big time trouble if things are not right and he meets up with the wrong person on the road.