Leaf and tiller growth ofLolium perenneandAgrostisspp. and leaf appearance rates ofTrifolium repensin set-stocked and rotationally grazed hill pastures

Abstract

Growth components of Lolium perenne and Agrostis spp. tillers and Trifolium repens stolon apices were compared for one year under set stocking and rotational grazing with sheep on hill pastures which had had low and high levels of fertiliser input. Leaf appearance rates of L. perenne and Agrostis spp. were unaffected by grazing management or fertiliser level. Leaf appearance in T. repens was also largely unaffected by treatments except in summer when rotational grazing allowed some relief from defoliation stresses and leaf appearance rates were greater than under set stocking during 3 grazing rotations. T. repens leaf appearance rates were slower in winter and increased later in spring than the grasses. For most of the year, tiller bud development in L. perenne was well below the maximum possible because of mutual shading in dense swards (mean total tiller density 29700 tillers/m 2 under set stocking and 20 too/m2 under rotational grazing). L. perenne lamina lengths, tiller lengths, and leaf extension rates were approximately twice those of Agrostis spp. Leaf extension rates were faster under rotational grazing for L. perenne and Agrostis spp. but tiller densities of both species were greater under set stocking. Total leaf growth per unit area is, therefore, likely to be similar under both managements. Slightly greater L. perenne growth and less Agrostis spp. growth per unit area under rotational grazing than under set stocking is indicated by a comparison of individual tiller growth and tiller density data. The results are discussed in relation to published findings from the same systems.

Effect of spring grazing management on perennial ryegrass and ryegrass‐white clover pastures

“…Figures 1 and 2 indicate that tillering was most rapid between November and February, with the highest tiller appearance rate at the end of December, soon after interruption of reproductive growth, particularly in release treatments (Tables 6 and 7). A similar period of intense tillering by perennial ryegrass during late spring and early summer has been observed previously in swards under grazing (Chapman et al 1983;Korte et al 1984;L'Huillier 1987;Matthew et al 1989b;Da Silva et al 1993, 1994 or cutting (Korte 1986). Table 9 Canonical structure and summary statistics for first discriminant factor for multiple discriminant analysis of herbage production (post-control period) and associated tiller demography measurements.…”

Morphogenetic adaptation to defoliation and soil fertility in perennial ryegrass (Lolium perenne)

“…The weekly defoliation in Experiment 1 at 5 mm height was more severe and led to a higher plant mortality than the 1-leaf treatment at 30 mm height in Experiment 2. Morphogenesis of Population R was similar to that described in situ by Chapman et al (1983), suggesting that growing conditions on Ballantrae soil under severe defoliation of Experiment 1 were a good simulation of those at Ballantrae. However, Curll & Wilkins (1982) showed that sheep at a high rate of set-stocking removed only 50-60% of leaf lamina at each defoliation, and never all leaves of a plant at one time.…”

“…Moreover, in hill country, ryegrass persistence involves not only withstanding defoliation and edaphic conditions, but also competitive ability, especially towards browntop. Tillers of browntop are about half the size of those of ryegrass (Chapman et al 1983) and so are proportionately less defoliated, giving browntop a competitive advantage through defoliation avoidance. Selection for defoliation avoidance in ryegrass may increase its competitive ability in hill country but at the same time decrease its yield potential.…”

“…The Resident ryegrass from Ballantrae had numerous small tillers with slow leaf elongation rate but rapid leaf appearance rate, leading to short leaves in all environments. The fine prostrate habit characteristic of New Zealand hillcountry ryegrass (Suckling& Forde 1978;Chapman et al 1983;Easton 1988;Wedderburn et al 1989) is not solely the expression of plasticity but also has a genetic basis. This population thus conforms to the observation that under continuous grazing and frequent defoliation, natural selection leads to plants with a fine prostrate habit enabling avoidance strategy (Warwick & Briggs 1978;Hazard & Ghesquiere 1995).…”

A Novel Approach to Grass–Legume Management

“…The rate of appearance of white clover leaves were slower in winter and increased later in spring than companion grass in the hill country of New Zealand (Chapman et al, 1983). Butcher et al (1996) suggested that leaf and stolon senescence have an important impact on the persistence of the legume in pasture.…”