Abstract: The discs used in rotary fertilizer spreaders are flat or cone-shaped. Contrary to flat discs, the cone-shaped discs throw fertilizer with an upward component of velocity and increase the distribution distance. In previous studies, the effect of cone-shaped discs on fertilizer distribution uniformity has not been investigated. In this study, therefore, the effect of the cone angle and the revolution speed of disc on the distribution uniformity were investigated with different flow rates using triple superphosphate. The best distribution uniformity was obtained from the combination between the disc cone angle of 0° and the disc revolution speed of 810 min-1 with the orifice diameter of 30 mm. Distribution uniformity became worse as the cone angle of disc increased (0°-flat disc, 10° and 20°) and became better as the revolution speed of disc increased (405, 540 and 810 min-1) with all the diameters of orifices (30, 40 and 50 mm).