A crop residue spreader for an agricultural harvesting machine, said spreader comprising: a pair of counter-rotating impellers (28, 30) disposed generally side by side below an inlet opening of the spreader; a discharge opening below the impellers (28, 30); a back plate behind the pair of impellers (28, 30); and a flow guide distributor apparatus comprising: - a flow guide element that has an apex portion and a pair of opposed laterally extending arm portions depending from the apex portion to free end portions (50, 52) and including surfaces defining crop residue flow surfaces (66, 68) that extend longitudinally between the fore and aft ends (54, 56) of the flow guide element, the flow guide element being disposed generally adjacent to the back plate of the spreader and generally intermediate to the impellers (28, 30), with the aft end generally proximate to the front side of the back plate, with the crop residue flow surfaces (66, 68) disposed beneath portions of impellers (28, 30), and with at least the free end portions (50, 52) disposed such that they extend sidewardly outwardly relative to said impeller portions; - an adjusting mechanism operable to adjustably vary the clearance between the outer swept diameters of the pair of impellers (28, 30) and the crop residue flow surfaces (66, 68) of the flow guide element to controllably distribute the crop residue in a desired pattern over a field; and - a coupling connector coupling the adjusting mechanism to the flow guide element, the adjusting mechanism being operable to effect directional movement of the complete guide element in at least one of vertical, horizontal, or rotational directions relative to the impellers (28, 30), characterised in that the adjusting mechanism comprises: a carrier assembly (100/260) coupled to the coupling connector and movable on wheels (106/266) along the back side of the back plate; and a drive assembly for effecting controlled movement of the carrier assembly (100/260) in response to input drive signals. a pair of counter-rotating impellers (28, 30) disposed generally side by side below an inlet opening of the spreader; a discharge opening below the impellers (28, 30); a back plate behind the pair of impellers (28, 30); and a flow guide distributor apparatus comprising: - a flow guide element that has an apex portion and a pair of opposed laterally extending arm portions depending from the apex portion to free end portions (50, 52) and including surfaces defining crop residue flow surfaces (66, 68) that extend longitudinally between the fore and aft ends (54, 56) of the flow guide element, the flow guide element being disposed generally adjacent to the back plate of the spreader and generally intermediate to the impellers (28, 30), with the aft end generally proximate to the front side of the back plate, with the crop residue flow surfaces (66, 68) disposed beneath portions of impellers (28, 30), and with at least the free end portions (50, 52) disposed such that they extend sidewardly outwardly relative to said impeller portions; - an adjusting mechanism operable to adjustably vary the clearance between the outer swept diameters of the pair of impellers (28, 30) and the crop residue flow surfaces (66, 68) of the flow guide element to controllably distribute the crop residue in a desired pattern over a field; and - a coupling connector coupling the adjusting mechanism to the flow guide element, - a flow guide element that has an apex portion and a pair of opposed laterally extending arm portions depending from the apex portion to free end portions (50, 52) and including surfaces defining crop residue flow surfaces (66, 68) that extend longitudinally between the fore and aft ends (54, 56) of the flow guide element, the flow guide element being disposed generally adjacent to the back plate of the spreader and generally intermediate to the impellers (28, 30), with the aft end generally proximate to the front side of the back plate, with the crop residue flow surfaces (66, 68) disposed beneath portions of impellers (28, 30), and with at least the free end portions (50, 52) disposed such that they extend sidewardly outwardly relative to said impeller portions; - an adjusting mechanism operable to adjustably vary the clearance between the outer swept diameters of the pair of impellers (28, 30) and the crop residue flow surfaces (66, 68) of the flow guide element to controllably distribute the crop residue in a desired pattern over a field; and - a coupling connector coupling the adjusting mechanism to the flow guide element, a carrier assembly (100/260) coupled to the coupling connector and movable on wheels (106/266) along the back side of the back plate; and a drive assembly for effecting controlled movement of the carrier assembly (100/260) in response to input drive signals.