Abstract: A sprinkler nozzle for a rotary sprinkler comprises two water flow passages extending therethrough, namely an upper passage and a parallel lower passage. The upper passage includes a straight, substantially cylindrical bore having stream straightening vanes, the upper passage watering radially outer portions of the watered pattern. The lower passage comprises a diffuser that reduces the energy of the water flowing into the lower passage by providing an expanded volume, namely a volume having a greater cross-sectional area than the cross-sectional area of the inlet. The water exits the diffuser through an outlet which includes a rear edge that forms an impact surface against which a portion of the boundary layer flow is directed. This impact surface is arch shaped and deflects the intercepted portion of the boundary layer flow from the top to the bottom of the lower passage. The boundary layer flow is then dumped onto a lower ramp of the outlet of the lower passage which lower ramp is downwardly inclined.