An agricultural baler, comprising: a bale chamber for the compression of crop material into bales, the bale chamber having a floor, a ceiling, a first wall and a second wall, wherein a bale forming direction of the bale chamber extends from an inlet end to an outlet end of the bale chamber, and wherein the floor comprises an inlet opening; a plunger for forcing the crop material from the inlet end of the bale chamber towards the outlet end of the bale chamber; a feeder duct communicating with the bale chamber through the inlet opening for charges of crop material to be transferred from the feeder duct into the bale chamber, wherein the feeder duct has an upper end facing generally upwardly and communicating with the inlet opening in the bale chamber and a lower end facing generally in a forward direction, the feeder duct has a top wall and a bottom wall extending between the lower end and the upper end of the feeder duct, wherein the top wall and / or the bottom wall (635, 637) are movable in order to adjust the volume of the feeder duct; a rotor feeder unit comprising: a rotor feeder carrying a set of tines, said rotor feeder being rotatable about an axis of rotation; a rotor feeder unit bottom distant from the rotor feeder forming a lower boundary of a conveying channel through the rotor feeder unit; and scrapers placed in a conveying direction behind the rotor feeder, the scrapers extending in between the tines and having a leading face cooperating with the tines; and a position adjuster configured to: displace the leading face of the scrapers relative to the rotor feeder unit bottom, and displace the top wall and / or the bottom wall (635, 637) of the feeder duct, in order to adjust the volume of the feeder duct. a bale chamber for the compression of crop material into bales, the bale chamber having a floor, a ceiling, a first wall and a second wall, wherein a bale forming direction of the bale chamber extends from an inlet end to an outlet end of the bale chamber, and wherein the floor comprises an inlet opening; a plunger for forcing the crop material from the inlet end of the bale chamber towards the outlet end of the bale chamber; a feeder duct communicating with the bale chamber through the inlet opening for charges of crop material to be transferred from the feeder duct into the bale chamber, wherein the feeder duct has an upper end facing generally upwardly and communicating with the inlet opening in the bale chamber and a lower end facing generally in a forward direction, the feeder duct has a top wall and a bottom wall extending between the lower end and the upper end of the feeder duct, wherein the top wall and / or the bottom wall (635, 637) are movable in order to adjust the volume of the feeder duct; a rotor feeder unit comprising: a rotor feeder carrying a set of tines, said rotor feeder being rotatable about an axis of rotation; a rotor feeder unit bottom distant from the rotor feeder forming a lower boundary of a conveying channel through the rotor feeder unit; and scrapers placed in a conveying direction behind the rotor feeder, the scrapers extending in between the tines and having a leading face cooperating with the tines; and a rotor feeder carrying a set of tines, said rotor feeder being rotatable about an axis of rotation; a rotor feeder unit bottom distant from the rotor feeder forming a lower boundary of a conveying channel through the rotor feeder unit; and scrapers placed in a conveying direction behind the rotor feeder, the scrapers extending in between the tines and having a leading face cooperating with the tines; and a position adjuster configured to: displace the leading face of the scrapers relative to the rotor feeder unit bottom, and displace the top wall and / or the bottom wall (635, 637) of the feeder duct, in order to adjust the volume of the feeder duct. displace the leading face of the scrapers relative to the rotor feeder unit bottom, and displace the top wall and / or the bottom wall (635, 637) of the feeder duct, in order to adjust the volume of the feeder duct.