The truck cannot be used for hire.
The truck must be used exclusively in connection with a farming operation, including a farmer hauling livestock or farm equipment for other farmers for compensation of any kind except money, or used for the transportation of the farmer and the farmer's family.
The vehicle cannot be used in connection with other gainful employment other than farming or ranching.
unlawful use of a Farm plate may result in a misdemeanor citation issued by a law enforcement agency. The agency may also confiscate the Farm plate.
Depending how the LLC for the farm is set up and state regs it is legal.