As I said before, check with your local DMV to be sure. I did check out the Oregon DMV website and found this about farm vehicles with air brakes.........
"Farm Endorsement
Persons may obtain a farm endorsement on a Regular Driver License (non-commercial Class C), Provisional (non-commercial Class C) Driver License, or any Commercial Driver License (CDL).
This endorsed license authorizes the operation of commercial motor vehicles when:
Controlled or operated by a farmer;
Used to transport agricultural products, farm machinery, or farm supplies to and from a farm;
Not used in the operation of a common or contract motor carrier; and
Operated within 150 miles of the farmer’s farm.
A farm endorsement does include vehicles equipped with air brakes and/or hauling hazardous materials.
A farm endorsement does not allow the transportation of farm workers or other passengers. If the driver transports passengers, a CDL with a passenger endorsement is needed."
This sounds like it covers you but again. check with your DMV!!