Any exchange pursuant to this subchapter of land that is subject to a mortgage contract with the Secretary of Agriculture under sections 1006a and 1006b of title 7, and any disposition pursuant to this subchapter of property that is subject to such a mortgage contract, shall be effected only in such form and manner and upon such terms and conditions as are consistent with the authority of the Secretary of Agriculture over such mortgage contract and such property under the Bankhead-Jones Farm Tenant Act, as amended [ et seq.], as supplemented by sections 1006a and 1006b of title 7.7 U.S.C. 1000