The shippers of watermelons in carload lots from any point within this State, before applying to any railroad, railway, common carrier or agent thereof for a bill of lading for any such shipment, shall first certify whether or not the watermelons contained in such shipment have been graded according to the standard of grades provided in § 39-17-310. Such certificate shall be made in writing on appropriate paper or cardboard, signed by the shipper in the presence of two disinterested witnesses, stating the variety, grade and number of melons contained in the car and the date the melons were picked and the date loaded or, if not graded, shall so state. The certificate shall be securely nailed to the inside of the car near the door and a duplicate of the certificate shall be furnished to the carrier’s agent.