A straw chopper for an agricultural harvesting unit includes a housing, and a rotor carried by the housing. The rotor includes a center chopping section and a pair of fans respectively positioned at longitudinally outboard ends of the center chopping section. Each fan includes a hub rotatable in a direction of rotation, and a plurality of fan blades connected with the hub at a plurality of angularly spaced locations about the hub. Each fan blade has a generally U-shaped portion with a rear wall and a pair of side walls extending from the rear wall in the direction of rotation.