A combine harvester has at its rear end separate chaff (10) and crop residue (12) discharge openings. A chopper (16) is provided for cutting the crop residue into small pieces, and a chaff discharge device (14) serves to disperse the chaff exiting from the chaff discharge opening (10). The chaff discharge device (14) is movable between a first position (14a) in which chaff can fall to the ground without passing through the chaff discharge device to lie in a string behind the combine harvester and a second position (14) in which the chaff passes through the chaff discharge device and is dispersed laterally away from the combine harvester. The chaff discharge device (14) is further movable to a third position (14b) in which chaff leaving the chaff discharge device is directed to enter the chopper (16) through an opening that is different from the opening through which the crop residue is admitted into the chopper (16). In this way, a blast from the chaff discharge device (14) carrying the chaff acts to keep the chopper (16) clean and assists it in dispersing the crop residue.
