Tenn. Code Ann. § 47-13-119

This chapter shall not prevent any person from making a mortgage, deed of trust, or security agreement under the Uniform Commercial Code to secure the payment for property bought or money lent, or for necessary advancements of supplies, stock, or farming implements to be made, to enable the owner of crops to make and save the same; provided, that the mortgage, deed of trust, or security agreement is executed at the time of buying the property, or borrowing the money, or making the contract for the advancements to be made, if the mortgage, deed of trust, or security agreement fixes the amount of advancement to be made under the contract.