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

Abstract

Abstract Growth components of Lotium 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/m2 under set stocking and 20 l00/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.