The responses ofPhalaris tuberosaL. to cutting to 1/2‐ and to 3‐in. at 3 levels of nitrogen (0, 23 and 92 lb/ac after each cut) were investigated in two irrigated, small‐plot trials. A technique involving the use of sheet‐iron borders embedded in the soil to contain root systems, irrigation water and fertilizer was developed. The 3‐in. cutting height gave greater dry‐matter yields than J in., the difference reaching significance only with applied N. Plant mortality was significantly greater for the 1/2‐in. cutting height at each N level. N significantly increased DM yield at both cutting heights, the greatest yield being at the higher application rate. Plant mortality at both cutting heights was significantly reduced by applied N. The results are discussed in relation to the most suitable grazing management for sustained growth of irrigatedP