A comparison of diploid and tetraploid perennial ryegrass and tetraploid ryegrass/white clover swards under continuous sheep stocking at controlled sward heights: 1. Sward characteristics

Swift, G.; Vipond, J.E.; Mcclelland, T.H.; Cleland, A.T.; Milne, J.A.; Hunter, E.A.

Grass and Forage Science 48(3): 279-289

1993


ISSN/ISBN: 0142-5242
DOI: 10.1111/j.1365-2494.1993.tb01861.x
Accession: 008031023

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Abstract
Two 1.0 ha plots of a late-heading diploid perennial ryegrass (var. Contender) and a late-heading tetraploid ryegrass (var. Condesa), and two 1.4 ha plots of the tetraploid with Aberystwyth S184 small-leaved white clover, were direct sown in May 1987. Over the three years 1988-90 they were continuously stocked by Mule ewes with Suffolk-cross twin lambs, from early April to the end of August, at a target sward surface height (SSH) of 4-6 cm on one set of plots (constant swards) and, on the other set, at 4-6 cm rising after June to a target 6-8 cm (rising swards). The heights were achieved by variable stocking. Fertilizer N was applied only to the grass plots at the rate of 150180 kg N ha-I annually. SSH was mainly within the target 4-6 cm, after higher initial heights at turnout in 1988 and 1990. Mean heights of the constant swards (April-August) averaged 5.53, 4.43 and 5.04 cm in the three years. The rising swards (July-August) increased in height over the constant swards by an average of 0.88, 0.48 and 0.55 cm, in successive years. Clover content of the herbage mass dry matter in the grass/clover swards increased over each grazing season to average 13.0, 26.5 and 21.2% in the three years, with a high mean stolon density of 130 m m-2 in August 1990. Ryegrass tiller densities in year 3 were 23% higher in the diploid than in the tetraploid swards, which had 43% more than the 10 000 tillers m-2 of the tetraploid ryegrass/clover swards. It is concluded that the combination of a densely stoloniferous small-leaved clover with the open growth habit of a tetraploid ryegrass can achieve swards of high clover content under continuous sheep stocking.

A comparison of diploid and tetraploid perennial ryegrass and tetraploid ryegrass/white clover swards under continuous sheep stocking at controlled sward heights: 1. Sward characteristics