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 i n the Netherlands has led to renewed interest in white clover. Therefore, t he performance of a newly sown perennial ryegrass/white clover sward on cla y soil was assessed during 4 consecutive years. The experiment consisted of all combinations of two defoliation systems, i.e, one or two silage cuts p er 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 cutti ng, 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 th an with S1, 6% higher with No than with N-50 and 12% higher with CO than wi th 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 relati vely wetter years, the annual DM yield was 1.19 t ha(-1) higher with RGC: t han 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. Herbag e quality was not affected by the experimental treatments. The average in v itro 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 fert ilizer N, perennial ryegrass/white clover swards should be seriously consid ered as an alternative option to perennial ryegrass swards on these clay so ils.