Dry-matter yield and herbage quality of a perennial ryegrass white clover sward in a rotational grazing and cutting system

The expected reduction in the use of fertilizer nitrogen (N) on grassland in the Netherlands has led to renewed interest in white clover. Therefore, the performance of a newly sown perennial ryegrass/white clover sward on clay soil was assessed during 4 consecutive years. The experiment consisted of all combinations of two defoliation systems, i.e, one or two silage cuts per year (S1, S2), spring N application rate, i.e. 0 or 50 kg ha(-1) year(-1) (N-0, N-50), and the management system, i.e. rotational grazing and cutting, or cutting only (RGC, CO). The overall mean white clover cover was 30%. All treatments affected white clover cover, which was 8% higher with S2 than with S1, 6% higher with No than with N-50 and 12% higher with CO than with RGC. The overall mean annual dry-matter (DM) yield (13.1 t ha(-1) year(-1)) was significantly affected only by the management system: in two relatively wetter years, the annual DM yield was 1.19 t ha(-1) higher with RGC: than with CO, whereas there was no difference in two relatively drier years. Nitrogen application increased the DM yield in the first cut by 7.0 kg kg(-1) N applied, but had no significant effect on the annual DM yield. Herbage quality was not affected by the experimental treatments. The average in vitro organic matter digestibility was 0.801, and the average crude protein content was 193 g kg(-1) DM. With the expected reduction in the use of fertilizer N, perennial ryegrass/white clover swards should be seriously considered as an alternative option to perennial ryegrass swards on these clay soils.