In the case of a pledge or mortgage of corn as security for a loan under the federal price support program or other government agricultural loan programs, the fee shall be deducted from the proceeds of such loan at the time the loan is made. If, within the life of the loan plus thirty days after the collection of a fee for corn that is mortgaged as security for a loan under the federal price support program or other government agricultural loan programs, the grower decides to purchase the corn and use it as feed, the grower shall be entitled to a refund of the checkoff fee previously paid. The refund shall be payable by the board upon the grower’s written application to the board for a refund of the amount deducted. Each application for a refund by a grower shall have attached thereto proof of the tax deducted.