An agricultural machine displaceable in a predetermined travel direction and having relative thereto a plurality of forwardly extending arms forming forwardly open throats for receiving respective rows of a crop during harvesting thereof has a position-detecting system comprising a feeler pivoted about an upright axis underneath each of the arms. Each feeler is an elastically flexible plate carried on a rigid arm connected to the respective pivot and each plate has a pair of lateral edges each exposed in front of a respective one of the throats flanking the respective plate. The feelers are all mechanically connected for joint pivoting by a common link that is connected to a signal generator in turn connected to the steering system of the agricultural machine.
