Abstract: A vehicle-borne spray boom apparatus has multiple articulated sections that are foldable and individually supported with respect to the ground to maintain a consistent and optimal distance between the boom sections and the ground on hilly and uneven terrain. A center section of the boom is mounted on a forward facing frame element of the vehicle, and boom arms extending from either end of the center section each comprise at least first and second sections, each supported by a ground-engaging wheel. Each first section is coupled at one end to the center section to permit vertical inclination with respect to the center section, and each second section is coupled at one end to a respective first section to permit vertical inclination with respect to such first section.