Before any lands under the jurisdiction and control of the Commissioners of the Land Office, covered by preference right leases and the improvements located on the land are owned by the lessees, shall be offered for sale and sold, the Commissioners of the Land Office shall cause the same to be appraised by three disinterested appraisers, who are nonresidents of the county in which the land is situated, to be selected by the Secretary. The appraisers, before entering upon their duties, shall take and subscribe the oath required of state officers. The appraisers shall make a true appraisement of the lands at the actual cash value thereof, exclusive of all improvements, and shall separately appraise all improvements owned by the lessee which can be removed without manifest injury to the land.