A conditioner unit (6) for conditioning crop material comprises a rotor (17) having a shaft (18) that carries a plurality of conditioning elements, a drive mechanism for driving rotation of the rotor (17) about an axis, and a deflector element having a working surface (26) that surrounds at least part of the circumference of the rotor (17) to define a conditioning passage through which crop material is transported by rotation of the rotor (17). An adjusting mechanism (30) is provided for adjusting the position of the deflector element relative to the rotor (17), the adjusting mechanism (30) including an actuator (50), a sensor for sensing an operational condition of the conditioning unit (6) and a control system (56) that receives a sensor signal from the sensor and controls actuation of the actuator (50) in response to said sensor signal to provide a desired level of conditioning during operation of the conditioner unit (6).
