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The effect of four commonly used dairy farm management systems (treatments), on nitrogen leaching to 1 m was studied over a 4-year period from October 2001 to April 2005. The treatments were (i) grazed plots receiving dirty water, (ii) 2-cut silage plots receiving slurry, (iii) grazed plots and (iv) 1-cut silage plots receiving slurry. All plots had fertiliser N applied; the soil was free-draining overlying fissured limestone. Mean 4-year N input (kg/ha) was 319 and mean annual stocking density was ∼2.38 LU/ha. The annual average and weekly NO₃-N and NH₄-N concentrations in drainage water were analysed for all years, using a repeated measures analysis. For the annual NO₃-N data, there was an interaction between treatment and year (P < 0.001). There were significant differences (P < 0.05) in NO₃-N concentrations between the treatments in all years except the third. For the NH₄-N data there was no …