Spring grazing management and tiller dynamics in a ryegrass/white clover pasture

Abstract

The objective of this trial was to study the effect of variation in the timing and duration of lax spring grazing on tiller dynamics in perennial ryegrass. Tiller population density, tiller appearance, and tiller death were measured in a sward of perennial ryegrass (cv. Grasslands Nui) and white clover (cv. Grasslands Tahora) grazed by sheep every 14 days to 4 cm (hard) and every 21 days to 7 cm (lax) residues. The experiment comprised 2 lax spring grazing treatments [lax grazing October 26December 8 (H-H-L-H) and September 16 December 8 (H-L-L-H)], plus a hard grazed control (H-H-H-H). Ryegrass tiller density was greater in H-L-L-H than H-H-L-H and H-H-H-H from mid summer until the end of the trial in autumn, mainly because of the difference in tillering activity late in December. Tiller appearance rate increased in all the treatments from September to the end of January, and was particularly high late in December in the second regrowth after grazing of the apices of the main group of reproductive tillers. The lax grazing management strategy increased tiller appearance rate during late December and January. Higher tiller losses in lax grazing treatments over the same period were not offset enough to affect this advantage. The response in tiller population density was greater following the extended period of lax spring grazing. Keywords: grazing management,Lolium perenne, reproductive growth, tiller population density, tiller demography, Trifolium repens