An improved field marker is provided which can be used on an agricultural implement of the type which includes wing folding. The field marker has an arm with a disk mounted on an outer end of the arm and a mounting system at the inner end of the arm for supporting the arm on the implement. The arm includes two portions which fold in a knee type action while the inner portion is folded through 90.degree. so that both portions lie along the side of the implement. The mounting assembly includes a fixed portion attached to the implement and a pivotal portion which moves about a horizontal axis. A spring biases the arm towards a raised position. In the extended position of the arm the spring force is overcome and the disk rests on the ground. As the arm retracts to the folded position and the effective weight decreases the spring forces lift the arm.