The Secretary shall take as security for the obligations entered into in connection with loans, mortgages on farms with respect to which such loans are made or such other security as the Secretary may require, and for obligations in connection with loans to associations under section
1926 of this title, shall take liens on the facility or such other security as he may determine to be necessary. Such security instruments may constitute liens running to the United States notwithstanding the fact that the notes may be held by lenders other than the United States. A borrower may use the same collateral to secure two or more loans made, insured, or guaranteed under this subchapter, except that the outstanding amount of such loans may not exceed the total value of the collateral so used.