Soil-displacing screw auger which contains an auger tube (1); a double displacement body (2) equipped with a hollow shaft (8) fixed to the auger tube (1) and containing an upper part (6) which constitutes a closed screw the radius of which increases towards its lower extremity and a lower part (7) which constitutes a closed screw the radius of which decreases towards its lower extremity, preferably with the same pitch as the upper part (6); a lower tube the diameter of which is smaller than twice the largest radius (R2) of the displacement body and which is situated between the lower part (7) of the displacement body (2) and the lower extremity of the auger; a screw blade (4) welded onto the outer casing of the lower tube, which rotates in the same sense as the lower part (7) of the displacement body (2) and an auger tip (5) connected to the lower extremity of the lower tube, with the special characteristic that the lower tube of the auger is an intermediate tube (3) with an outer diameter (D3) which is smaller than twice the largest radius (R2) of the displacement body (2) but larger than the outer diameter (D1) of the auger tube (1), whereas the auger tip (5) contains a displacement part (16) with a closed screw rotating in the same sense as the screw blade (4) on the intermediate tube (3) and a maximal radius equalling half the diameter (D3) of the intermediate tube (3).