From and after thirty days from February 11, 1936 the restricted lands belonging to Indians of the Five Civilized Tribes in Oklahoma of one-half or more Indian blood, enrolled or unenrolled, may be leased for periods of not to exceed five years for farming and grazing purposes, under such rules and regulations as the Secretary of the Interior may prescribe and not otherwise. Such leases shall be made by the owner or owners of such lands, if adults, subject to approval by the superintendent or other official in charge of the Five Civilized Tribes Agency, and by such superintendent or other official in charge of said agency in cases of minors and of Indians who are non compos mentis.