Some factors affecting the persistency of short-rotation ryegrass

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Abstract
A study was made of the extent of stem elongation and seed-head emergence occurring in short-rotation ryegrass pastures during the reproductive period of growth. Pastures under both lax and continuous grazing treatments were compared. Data for short-rotation ryegrass were compared with those obtained for perennial ryegrass. For both ryegrass varieties tiller numbers per unit area were significantly higher in the continuously-grazed pastures, while for both grazing treatments tiller numbers were significantly higher in the perennial ryegrass stands. The percentages of tillers with elongated stems and emerged seed-heads were highest in the short-rotation ryegrass pastures, particularly under lax grazing. These higher percentages occurred later than in the perennial ryegrass pastures, although the period over which elongation and emergence occurred was more prolonged. These results are discussed in relation to: (1) the persistency of short-rotation ryegrass in pastures, particularly where hard grazings are practised during the drier summer months; and (2) changes in the genotypic structure of the variety under different systems of pasture management.