ORS § 308A.306
An owner of land desiring current open space use assessment under ORS 308A.300 to 308A.330 shall make application to the county assessor upon forms prepared by the Department of Revenue and supplied by the county assessor. The owner shall describe the land for which classification is requested, the current open space use or uses of the land, and shall designate the paragraph of ORS 308A.300(1) under which each such use falls. The application shall include such other information as is reasonably necessary to properly classify an area of land under ORS 308A.300 to 308A.330 with a verification of the truth thereof. Applications shall be made to the county assessor during the calendar year preceding the first assessment year for which such classification is requested. If the ownership of all property included in the application remains unchanged, a new application is not required after the first year for which application was made and approved.
ORS 308A.306