SEASONAL-VARIATION IN GROWTH-CHARACTERISTICS OF LOLIUM-PERENNE AND TRIFOLIUM-REPENS IN SWARDS UNDER DIFFERENT MANAGEMENTS

In a range of perennial ryegrass/white clover swards, variation in the surface heights of the grass and clover components, the rates of incr ease of these surface heights and the specific leaf areas (SLAs) of ry egrass and white clover were described for 1 year. The swards were of an early- or late-flowering (Aurora or Melle respectively) perennial r yegrass variety growing with either a small- or a medium-leaved (Kent or Milkanova) white clover and were either continuously stocked by she ep or continuously stocked apart from a rest period in April-May (Auro ra) or May-June (Melle). The surface heights of grass and clover were not affected by the variety of their companion species, and the surfac e heights of the two clover varieties were similar. The grass was alwa ys taller than the clover, although the magnitude of the difference be tween the species varied with time of year and the timing of the rest period. Before the summer solstice the rate of increase in height of g rass was greater than that of clover except at cool temperatures (5-de grees-C) and warm temperatures (16-degrees-C), and in the unrested Mel le sward. After the solstice the rates of increase in height, particul arly of clover, were lower than the rates seen at similar temperatures before the solstice. Overall, the SLAs of both clover varieties were greater than those of ryegrass when grwon with Aurora but not when gro wn with Melle, and the SLAs of both species increased during the year. BY October the SLAs of both grass varieties were less than those of t heir companion clovers. The results are discussed in relation to their implications for the species composition of the swards.