Tiller size/population density in grazed swards of Cynodon spp. / Compensação tamanho/densidade populacional de perfilhos em pastagens de Cynodon spp.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2000

RESUMO

The experiment was conducted at the Department of Animal Production, ESALQ/USP, Piracicaba (SP), from 15/12/98 until 04/07/99. Treatments were combinations of three Cynodon spp. cultivars (Tifton-85, Florakirk and Coastcross) and four sward surface heights (SSH) (5, 10, 15 and 20 cm) maintained by sheep under continuous stocking and variable stocking rate. A complete randomised block design was used, with treatments arranged in split-plot and replicated four times. Grass cultivars were assigned to plots and SSH to sub-plots. Pastures responses evaluated were: total biomass above ground level, tiller population density, tiller weight, leaf mass and leaf area per tiller. From these measurements calculations of sward leaf area index (LAI), tiller volume, tiller leaf:stem ratio and tiller leaf area:volume ratio (R) were derived. A tiller size/population density mechanism operated in Cynodon spp. However, a slope steeper than the theoretical expectation of 3/2 was observed. Individual tillers presented an isometric pattern of growth and seemed to demonstrate a clonal integration among tillers in order to enhance competitive ability and optimise LAI. Swards maintained at 5 cm during autumn presented reduced tiller population densities, indicating a pattern of grazing tolerance dependent of time of the year. Tifton-85 and Coastcross pastures showed a capacity to increase total biomass that could go beyond 20 cm, while Florakirk stabilised around that SSH. Reproductive development of plants interfered with the processes related to intra-specific competition and tiller population dynamics.

ASSUNTO(S)

cinodonte densidade populacional pastagem cynodon forage grass tiller population density pasture tillering altura de planta sward height gramínea forrageira perfilhação cultivar rariedade

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