Sward Height in Grazing Management: Species Adaptation

Under continental, northern conditions, yield potential of species such as perennial ryegrass (Loli11111 pere,me L.) and white clover (Trifolium repe,is L.) is considered to be inferior to that of taller, coarser species such as orchardgrass, bromegrass, timothy and alfalfa. However, recent species evaluation bas stressed management regimes characteristic of conserved feed rather than pasture production, In a replicated trial, species performance and persistence in mixture were evaluated in response to sward height-based grazing management. Starling in 1990, 2 swards constructed predominantly of fine- or coarse-stemmed grasses were grazed rotationally by cattle, using a common 20-25 cm entry height and a 5 or a JO cm residual height. Grass biomass and tillering, dead biomass, and white clover content were 16, 19, 19 and 31% greater in fine than in coarse swards, but proportion of total biomass contributed by grass, by the dominant perennial ryegrass, by dead biomass, or by while clover did not vary with sward type. Grazing lo a 10 cm residue increased dead biomass by 30%, and decreased white clover yield and petiole density by 32 and 42%, respectively, without affecting grass biomass or tillering. Jn this first-year sward, interactions among the components of the fine swards produced a higher yield without altering the balance of grass:dead:clover material from that in the coarse swards. Convessely, residual height altered the balance between dead material and white clover, without affecting yield or tillering of the dominant grass component. Effect of residual grazing height was consistent across both sward types.