Pasture species complementarity leading to increased dry matter (DM) production has been observed in multispecies (MS) swards which include legumes and forage herbs along with grasses. This effect has been measured in mechanically defoliated plots with little data available from grazing scenarios. There is a scarcity of data available regarding individual forage herb species contribution to increased sward DM production where only plant functional group has been monitored previously. The objective of this three year study was to assess the DM production, N fertiliser response and change of botanical composition in grazed plots across nine MS sward mixtures compared to a PRG monoculture. Multispecies swards included various combinations of species from the three plant functional groups; N fertiliser treatments of 0, 100, 150 and 200 kg N/ha/year were applied. While year influenced the effect of sward mixture on annual DM production, swards that included white clover (Trifolium repens. L.) produced an average of 1688 kg DM/ha/year more than those which did not (P < 0.05); including forage herbs did not increase either annual or seasonal sward DM production. In the final year of the study sward chicory (Chicorium intybus. L.) content was 5% in mixtures including three plant functional groups while ribwort plantain (Plantago lanceolate. L.; PL) content was 37% in the same sward types. Although PL did not increase grazed sward DM production in the current study it did persist well under grazing and may provide other beneficial ecosystem services in dairy grazing systems.

Abstract Background Recently, there has been increasing interest in the use of multispecies (MS) swards in dairy grazing systems. Methods A plot grazing study was established to investigate the potential contribution of different sward species (perennial ryegrass, legumes and herbs) sown in grazing pastures. Ten sward mixtures were sown, ranging in complexity from a perennial ryegrass (PRG) monoculture to binary mixtures including either forage legumes or herbs to a five‐species mixture; four different nitrogen (N) application rates of 0, 100, 150 and 200 kg N ha−1 were applied to each sward. Results Species abundance for all sward species components was associated with the interaction of time point and sward mixture; species abundance for all sward components, except PRG, was associated with the interaction of N application and sward mixture. The interactions of time point and sward mixture, and time point and N application rate, were associated with all analysed sward chemical components, except for sward digestibility. Conclusions Increased N application rates reduced the level of clover in all sward mixtures. Increased levels of white clover led to increased sward crude protein levels; the inclusion of ribwort plantain led to some seasonal variation in the nutritive value of swards.