The square baler comprises a pick-up a pre-compression chamber, a baling chamber, a loading mechanism for transferring each slice of crop from the pre-compression chamber into the baling chamber and a plunger. The baler further can include at least one non-contact sensor that is provided in at least one of the walls of the pre-compression chamber and/or of the input zone of the baling chamber to produce an output signal indicative of the density of the crop.
