S.D. Codified Laws § 47-21-46.3
A mortgage or trust deed to secure a debt executed by a rural electric cooperative, covering the whole or part of its easements or other less than fee simple interests in real estate used in the transmission or distribution of electric service, and also covering the fixtures of the rural electric cooperative which are annexed to it, may be filed in the Office of the Secretary of State along with, or as part of, the financing statement covering the fixtures. The filing of the mortgage or deed of trust has the same effect, and is notice of the rights and interest of the mortgagee or trustee in the easements and other less than fee simple interest in real estate to the same extent as if the mortgage or deed of trust were duly recorded in the office of the register of deeds of each county in which the real estate is situated. The effectiveness of the filing terminates at the same time as provided in § 47-21-46.2 for the termination of the effectiveness of a fixture filing. For the purpose of this section, a mortgage or deed of trust filed under this section contains a sufficient description to give notice of the rights and interest of the mortgagee or trustee in the easements and other less than fee simple interest in the real estate used for the transmission and distribution of electric service of the rural electric cooperative if the mortgage or deed of trust states that the security includes easements, rights-of-way of, or transmission or distribution systems of, or lines of, the rural electric cooperative, or all property owned by the rural electric cooperative. A mortgage or deed of trust filed before July 1, 2009, pursuant to § 47-21-46, which complies with the provisions of this section, is considered filed and effective under this section as of July 1, 2009. Section 47-21-46 applies to real estate owned in fee simple by a rural electric cooperative. Any mortgage or deed of trust filed before July 1, 2009, with the Office of the Secretary of State pursuant to chapter 57A-9, that complies with the provisions of this section, is considered filed and effective under this section as of July 1, 2009.
SDCL 47-21-46.3