Oregon Revised Statutes Revenue and Taxation § 307.398

(a) “Center pivot” means a piece of self-propelled machinery that rotates around a riser for the purpose of sprinkling a circular tract of land. “Center pivot” includes all of the component parts of the center pivot irrigation system that are ordinarily located above the ground on the land to be irrigated and that can be disconnected from the riser and moved to another point. A center pivot constitutes personal property.

(b) “Center pivot irrigation system” means an irrigation system that uses pumping stations and pipelines to convey water from its source to a riser to which a center pivot may be connected and used for sprinkling.

(c) “Riser” means a pipe located in the field to be irrigated that rises vertically through the surface of the ground.