Abstract: A field marker for attachment to a farm implement to form a groove in the ground for guiding a farmer as the implement is towed or driven across a field includes an inner wing section pivotally connected to a lateral end of the implement and an outer arm section pivotally connected to the distal end of the wing section. The wing section may be pivoted hydraulically from a working position extending outwardly from the implement to a stowage position parallel to the implement. The arm section may be pivoted hydraulically generally vertically relative to the wing section through an angle of about 190.degree. between its stowage position and its working position. The arm section is provided with a spring-loaded breakaway mechanism that permits an outer arm portion of the arm section to pivot rearwardly of an inner arm portion of the arm section should the arm section encounter an immovable obstruction. The breakaway mechanism can be easily and quickly reset after activation without having to replace any parts.