S.D. Codified Laws § 46A-3B-4
A director candidate may be nominated by a petition signed by at least twenty-five registered voters in the director area to be represented by the candidate. Nominating petitions shall be made available at the water development district office, the secretary of state's office, and the respective county auditors' offices on forms prescribed by the state election board and filed with the secretary of state not prior to eight a.m., January first, and not later than five p.m., the last Tuesday of March prior to the date of the primary election. If a petition is mailed to the secretary of state's office by registered mail by five p.m., the last Tuesday of March prior to the primary election, it is considered filed. For the initial election, director nominating petitions shall be made available by the Department of Agriculture and Natural Resources and shall be filed with the department not later than five p.m., the first Tuesday of August before the general election or in the case of a special election under § 46A-3B-1, not later than thirty days before the date set for the special election.
SDCL 46A-3B-4