Harvesting combine having a forward end, a rear end and opposite outer sides extending longitudinally between the forward end and the rear end, the harvesting combine comprising: a power processing unit having a forward end and a rear end, wherein the power processing unit is positioned at the forward end of the harvesting combine and includes a concaves and grates assembly (58, 60) for threshing grain from material other than grain; a grain storage for storing threshed grain; a driving axle for drivingly supporting a set of wheels (28A, 28B) or a set of tracks so that the wheels or the tracks are maintained at a separation distance; main sieve assemblies (62, 64) arranged to receive grain and tailings from the concaves and grates assembly (58, 60), wherein the tailings are unthreshed material output from the concaves and grates assembly (58, 60) and primarily composed of material other than grain, the main sieve assemblies (62, 64) being adapted to separate grain from material other than grain of the tailings, wherein the main sieve assemblies (62, 64) extend over a primary separation and cleaning area longitudinally bounded between the concaves and grates assembly (58, 60) and the rear end of the harvesting combine and transversely bounded between the opposite outer sides of the harvesting combine, the primary separation and cleaning area having a transverse width smaller than the separation distance, such that the said primary separation and cleaning area is comprised between opposite boundaries spaced by the said transverse width, wherein the harvesting combine comprises additional sieve assemblies (70, 72) arranged to receive tailings from the concaves and grates assemblies (58, 60) and from the main sieve assemblies (62, 64) and adapted to perform additional separation of grain from the material other than grain, wherein the additional sieve assemblies (70, 72) are arranged between the concaves and grates assembly (58, 60) and the rear end of the harvesting combine at the outer sides of said combine so as to extend transversally beyond the boundaries of the primary separation and cleaning area, thereby defining an additional separation and cleaning area, characterised in that the additional separation and cleaning area extends longitudinally beyond the rear end of the primary separation and cleaning area a power processing unit having a forward end and a rear end, wherein the power processing unit is positioned at the forward end of the harvesting combine and includes a concaves and grates assembly (58, 60) for threshing grain from material other than grain; a grain storage for storing threshed grain; a driving axle for drivingly supporting a set of wheels (28A, 28B) or a set of tracks so that the wheels or the tracks are maintained at a separation distance; main sieve assemblies (62, 64) arranged to receive grain and tailings from the concaves and grates assembly (58, 60), wherein the tailings are unthreshed material output from the concaves and grates assembly (58, 60) and primarily composed of material other than grain, the main sieve assemblies (62, 64) being adapted to separate grain from material other than grain of the tailings, wherein the main sieve assemblies (62, 64) extend over a primary separation and cleaning area longitudinally bounded between the concaves and grates assembly (58, 60) and the rear end of the harvesting combine and transversely bounded between the opposite outer sides of the harvesting combine, the primary separation and cleaning area having a transverse width smaller than the separation distance, such that the said primary separation and cleaning area is comprised between opposite boundaries spaced by the said transverse width, wherein the harvesting combine comprises additional sieve assemblies (70, 72) arranged to receive tailings from the concaves and grates assemblies (58, 60) and from the main sieve assemblies (62, 64) and adapted to perform additional separation of grain from the material other than grain, wherein the additional sieve assemblies (70, 72) are arranged between the concaves and grates assembly (58, 60) and the rear end of the harvesting combine at the outer sides of said combine so as to extend transversally beyond the boundaries of the primary separation and cleaning area, thereby defining an additional separation and cleaning area, characterised in that the additional separation and cleaning area extends longitudinally beyond the rear end of the primary separation and cleaning area