A chopper for receiving the straw and/or chaff from a combine harvester includes a housing with a chopping rotor to transport the materials though a discharge opening onto a tailboard construction with downwardly facing guide surface and fins for spreading of the crop materials. A rotary spreader has a plurality of fan members with blades rotatable for discharge to a respective side of the rotary spreader. An arrangement is operable so that in a first mode the crop material is spread wholly by the tailboard and in a second mode the crop material is spread at least mainly by the rotary spreader. In the second mode the tailboard remains position above the rotary spreader which is therefore located underneath a guide surface with fins of the guide surface facing downwardly adjacent the blades. The movement to the second ode is provided by the rotary spreader being moved forwardly and downwardly.
