Pasture legume adaptation to six environments of the seasonally dry tropics of north Queensland

Abstract

Production, regeneration and persistence of summer-growing pasture legumes were studied in plots (26 accessions) in 3 sub-coastal environments (>600 m elevation) and in rows (92 accessions) in 3 inland environments (<200 m elevation) in the seasonally dry tropics of north Queensland. In the plots, the annuals Aeschynomene americana and Centrosema pascuorum and the perennials Stylosanthes scabra, S. hamata and Chamaecrista rotundifolia were most productive, yielding up to 4.5 and 7.6 t/ha DM, respectively, on grey and red earths and a red duplex soil. Annuals regenerated poorly in low rainfall years, but populations and production of the Stylosanthes species and C. rotundifolia cv. Wynn remained adequate for commercial pastures in all years, and increased in a high rainfall year. Macroptilium gracile cv. Maldonado was planted at only one site and produced a peak yield of 6.2 t/ha DM and had most spread (>30 m) during the experiment.
In the row experiments, legume establishment and production were restricted by drought on the red earth and grey clay soils, and by waterlogging on a hard-setting solodic soil. After 4 years of drought and grazing, none of the 72 legumes sown on the fertile red earth had survived, although there was subsequent regeneration from seed. Desmanthus species and Clitoria ternatea were most productive and persistent, over 15 years, on the cracking clay soil, and Stylosanthes scabra cv. Seca and S. hamata cv. Verano were the only survivors on the solodic soil. Environmental limitations of the current pasture legume cultivars have been identified and legume genera are suggested for further evaluation and development under commercial grazing management and for special purpose pastures in these environments.