For the combined operation of Cayron ploughs with Inversion packers such as, for example, the AMAZONE C-PACK, a hydraulically-released press arm is available. The press arm, with its spacious reach and distance to the plough, is adjustable on the move. The packer can be transported very close to the plough, avoiding any side forces. Due to its combination with the turnover cylinder, the hydraulic unlocking does not require an additional spool valve on the tractor. Retrofitting to the plough is also readily possible due to the fixing flange on the plough beam in front of the first body.