A device and method is disclosed for detection of cultivation boundaries or guide variables which are evaluated for an automatic steering system on agricultural machines. Electromagnetic waves emitted by a transmitter in the working direction of the machine are used. Several boundary-specific variables are determined from the reflection of the electromagnetic wave and from them is derived a control difference for a steering regulator.The device is mounted on the individual implements in the vicinity of the cultivation boundary and arranged in such a way that the cultivation boundary is detected before cultivation. Using a device, in the embodiment of a scanner, which works with electromagnetic waves, and evaluating several cultivation boundary-specific guide variables contained in the reflection, results in the successful contactless detection all cultivation boundaries or guide variables existing in agriculture. Further, evaluation methods for detecting different cultivation boundaries or guide variables are automatically selected with the aid of an appropriate selection method.