R.M. JONES

CSIRO Division of Tropical Crops and Pastures, 306 Carmody Road, St. Lucia, Qld, 4067, Australia.

Abstract

Two experiments in coastal south-east Queensland examined the effect of spelling on Siratro (Macroptilium atropurpureum) in Siratro/setaria (Setaria sphacelata) pastures where yield and density of Siratro were declining. Both experiments involved the use of small exclosures in established, continuously-grazed and set-stocked pastures. In an overgrazed pasture where Siratro and setaria were still the dominant species, both the legume and grass regained full productivity with 1 year's spelling. As overgrazing continued and the pasture degraded further, a longer rest period was required to restore productivity. In the final set of exclosures, the pasture did not fully recover even after 4 years of spelling.
The second study compared the effects of spelling (a) over the full growing season, (b) the second half of the growing season and (c) the first half of the growing season on a continuously grazed pasture that still had adequate but declining Siratro density. Spelling for the whole growing season increased seed set of Siratro by factors of 14, 5 and 79 in 3 successive years, while spelling for the second half of the growing season increased it by factors of 8, 4 and 25. Spelling also increased the presentation yield of Siratro. The implications of such increases are considered and it is suggested that spelling may be a practical method of maintaining Siratro in pastures.