ORS § 547.500
The board of supervisors of every drainage district which may elect to claim the benefits of ORS 547.495 to 547.515 shall file with the county clerk of the county in which the land is located, any time before the removal of the crop upon which a lien is desired, a statement verified by the oath of the secretary of the board or some person having knowledge of the facts, setting forth the amount of that portion of the annual charges or assessments for maintenance and operation levied against the land, or imposed upon the owners or occupants of the land, on which the crop is grown and for which a lien is desired, with a description of the land sufficient for identification, the name of the owner of the crop, or reputed owner if known, and the name of the owner of the land on which the crop is grown.
ORS 547.500