A conveyance, mortgage, deed of trust or other incumbrance upon a homestead exempted from execution shall not be valid or binding unless signed by the spouse of the owner if the owner is married and living with the spouse or by an attorney in fact for the spouse. But where the spouse of the owner of the homestead exempted from execution has been adjudicated incompetent, then the owner of the homestead may file a petition in the chancery court and allege in the petition the incompetence of the spouse and the adjudication of incompetency of the spouse and the facts of the case. The summons for the spouse who has been adjudicated incompetent shall be issued and be served in the same manner as process is served in other cases on persons who are incompetent. The court shall hear the case in vacation or in termtime as in other cases, and if the court finds the spouse to be incompetent and the owner entitled to relief, the court by decree shall authorize and empower the owner to execute a conveyance, mortgage, deed of trust or other incumbrance upon the homestead without the signature of the spouse. However, no mortgage or deed of trust executed in favor of the Farmers Home Administration at the time of the purchase of real estate to secure the payment of the money used to purchase the real estate shall be invalid because it is not signed by the spouse of the owner. All powers of attorney authorizing any conveyance, mortgage, deed of trust or other incumbrance upon a homestead shall designate an attorney in fact other than the spouse and shall comply with the provisions of Chapter 3 of Title 87.