A spreader (100) has a hopper or bin (1) for storing a spreadable material (2), a plurality of spinners (5, 6) adapted to receive the material from the hopper or bin and to spread the material (2) on the ground, and a Global Positioning System (GPS) receiver (8) for sensing the position of the spreader (100) and providing an output signal indicative of a position of the spreader to a controller (7). The controller (7) calculates a required pattern and density of material (2) to be spread by the spinners (5, 6) based on a comparison of the actual position of the spreader (A) to a preferred position of the spreader (I), and controls the spinners (5, 6) in order to obtain the required pattern and density of spread material (2). A method of controlling the pattern and density of material spread by a spreader is also disclosed.
