A centrifugal spreader (21) for spreading soil improvement material, in particular farmyard manure, on a field, wherein the centrifugal spreader (21) includes at least one rotor (27) on an upright rotor shaft (26). The rotor (27) is disposed under a supply unit (22) for supplying the soil improvement material to the rotor (27), and the rotor (27) includes spreader arms (25) for flinging the soil improvement material out during rotation. The rotor (27) includes a surface area (36) extending around the rotor shaft (26), provided at a position under the spreader arms (25). Furthermore, there is provided at least one stationary shearing edge (34) in contact with this surface area (36) or spaced less than 5 mm apart from this surface area (36), adapted to cut strings or cords carried by the rotor (27) along this surface area (36) in order thereby to prevent any strings or cords carried with the soil improvement material to be wound around the rotor (27) or the rotor shaft (26).
