Tropical Grasslands (1989) Volume 23, 43–55

PRODUCTIVITY AND POPULATION DYNAMICS OF SILVERLEAF DESMODIUM (DESMODIUM UNCINATUM), GREENLEAF DESMODIUM (D. INTORTUM) AND TWO D. INTORTUM × D. SANDWICENSE HYBRIDS AT TWO STOCKING RATES IN COASTAL SOUTH-EAST QUEENSLAND

R.M. JONES

CSIRO Division of Tropical Crops and Pastures, Cunningham Laboratory, 306 Carmody Road, St. Lucia, Queensland 4067.

Abstract

An experiment was conducted in coastal south-east Queensland to compare the persistence and productivity of Desmodium intortum cv. Greenleaf, Desmodium uncinatum cv. Silverleaf and 2 D. intortum × D. sandwicense hybrids selected for early seeding and large seed size. The legumes were sown with Setaria sphacelata cv. Nandi and stocked at 1.1 and 1.9 beasts/ha. Initially Greenleaf was the most productive legume under good growing conditions. However Silverleaf was more persistent over a 7-year period.
After 3 years, only 10% of the original taproots of Greenleaf and the 2 hybrids were alive compared with 50% of Silverleaf roots. However after 7 years there were very few (< 2%) of Silverleaf taproots still alive. All desmodium lines relied on adventitious rooting from stolons for long term persistence. Persistence and presentation yields of desmodium were markedly depressed by dry conditions. This, to a considerable extent, is attributed to damage on the larger roots caused by weevil (Amnemus quadrituberculatus) larvae, with Silverleaf being the least effected line. There was negligible successful recruitment from desmodium seedlings. Presentation yields, soil seed reserves and stolon length were depressed at the higher stocking rate. The results are discussed in relation to site selection and grazing management of D. intortum and D. uncinatum pastures and to the potential for selecting lines with better persistence.

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