Precision farming requires yield maps of all harvested crops. In order to monitor the yield of forage crops a round baler has been equipped with a weighing system. It was based on a load cell in the drawbar coupling and strain gauges in the axle. Tests were first carried out in static mode; the weights of bales could be determined with errors of less than 1%. Afterwards the suitability of the system for weighing on-the-move was examined. With signal smoothing methods spurious oscillation in the signals could be eliminated. Further investigations are necessary for reducing the remaining errors of up to 10%.