D.A. IVORY

Queensland Wheat Research Institute, 13 Holberton Street, Toowoomba, Qld 4350.

Abstract

The seasonal and annual productivities of Festuca arundinacea (tall fescue) cv. Demeter and cv. Alta Phalaris aquatica (syn. P. tuberosa) cv. Australian cv. Sirocco and cv. Sirosa, Lolium perenne (ryegrass) cv. Kangaroo Valley, Dactylis glomerata (cocksfoot) cv. Currie and Bromus unioloides (Priebe prarie grass) were studied at three sites on heavy clay soils on the eastern Darling Downs from 1976 to 1979. The grasses received 0 or 100 kg N ha^-1 or were grown with annual medics (Medicago truncatula cv. Jemalong and M. scutellata cv. Robinson) at Ramsay and Nobby or white clover (Trifolium repens cv. Ladino) at Geham. The performances of white colver or medics grown alone, and of lucerne (M. sativa cv. Hunter River) grown alone or with Demeter tall fescue, were also measured.
The most productive grasses were Demeter tall fescue, Sirosa and Australian phalaris and Currie cocksfoot. Nitrogen fertiliser increased the mean annual dry matter yield of these grasses from 2000 to 4600 kg ha^-1 at Geham (rainfall 756 mm yr^-1), from 2400 to 5600 kg ha^-1 at Ramsay (769 mm) and from 900 to 2300 kg ha^-1 at Nobby (580 mm). Mean annual dry matter yields of mixtures of grass and medics or white clover at these sites were 3800, 3150 and 1900 kg ha^-1 and the lucerne–Demeter mixtures yielded 4100, 4300 and 3900 kg ha^-1, respectively. Demeter persisted poorly with lucerne. There was no difference in grass yield when legumes were included at Geham or Ramsay but there was a 49% increase at Nobby. Differences in seasonality of growth occurred between grasses. Currie cocksfoot and the Phalaris cultivars were the most drought tolerant but all swards suffered invasion by annual and perennial summer-growing species. Mean annual protein yields were increased by 240% and 140% at Geham, 59% and 140% at Ramsay, and 260% and 200% at Nobby by the inclusion of a legume or application of N fertiliser respectively.