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The effect of different levels of applied nitrogen (N) (ranging from 120?720 kg N ha−1 a−1) on the root development of perennial ryegrass (Lolium perenne L.) was examined at the end of the establishment year. Increasing levels of applied N increased perennial ryegrass root organic matter (OM) content in the top 50 mm of the soil, while a corresponding decrease in root OM content was observed in the 100?200 mm soil depth category. Increasing levels of applied N did not have a significant effect on root OM content in the 50?100 mm or the overall 0?200 mm soil depth category. Lower levels of applied N (120?360 kg N ha−1 a−1) may be more conducive to promoting deeper root development than higher levels of applied N (480?720 kg N ha−1 a−1), but this would require investigation beyond one year. Perennial ryegrass is extremely shallow?rooted, with approximately 75 % of the root mass occurring in the top 50 mm of the soil. This stresses the need to pay careful attention to irrigation scheduling.