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

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, al 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 150‐ 180kgN ha‐1 annually. SSH was mainly within the target 4–6 cm, after higher initial heights at turnout in 1988and 1990. Mean heights of the constant swards (April‐ August) averaged 5·53, 4·43 and 5·04cm 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 in 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 10000 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 perennial ryegrass cultivars differing in heading date and grass ploidy with spring calving dairy cows grazed at two different stocking rates

“…This may be related to the lower DM production of the IH tetraploid cultivar. Diploid cultivars had higher bulk density, which agrees with the findings of [13,15,38]. The structure of the sward canopy is known to influence grass DMI.…”

Effects of clover and milk in the diet of grazed lambs on meat quality

“…Details of the botanical and chemical composition of the T and TC pasture types are given in Swift et al (1993). Botanical composition of diploid swards was similar to the tetraploid swards with proportionately 0-967 perennial ryegrass, 0-003 white clover (unsown), 0-029 annual meadow grass and 0-001 dicotyledonous weeds.…”

“…Full details of the sward composition, chemical analyses and management of the T and TC pastures are given in an earlier paper (Swift, Vipond, McClelland, Cleland, Milne and Hunter, 1993). Three pasture types were studied, a sward of perennial ryegrass, variety Contender, which is typical of traditionally sown late-heading diploid varieties (D), a sward of Condesa, a recently introduced late-heading tetraploid variety, (T) and a sward of Condesa/clover containing on average proportionately 0-19 of the dry matter as clover (TC).…”

Effects of clover in the diet of grazed lambs on production and carcass composition

“…For details on the establishment of these pastures and their relative lamb production over the first three grazing seasons see Swift, Vipond, McClelland, FitzSimons, Milne and Hunter (1993) and Vipond, Swift, McClelland, FitzSimons, Milne and Hunter (1993). In the previous 3 years, 1988-90 clover content of GC swards averaged 0-2 of herbage dry matter.…”