A sensor arrangement for detecting a density of harvested crops deposited as silage in a silo includes a source of a pressurized gaseous medium and an opening connected by a line to the source and which is movable along a surface of the silage. The gaseous medium is guided out of the opening from the source into the silage. The arrangement further includes a sensor for detecting a property of the medium flowing through the line, and an evaluation device connected to the sensor for providing an output signal containing information based on the signal of the sensor regarding the density of the silage.