Persistence of tropical pasture legumes in the moderate rainfall sub-tropics of eastern Australia

Abstract

Identifying pasture legume varieties that remain persistent and productive over the long-term has been a challenge in the moderate rainfall sub-tropics of eastern Australia. Although several legume cultivars considered adapted for clay soils were released in Australia in the mid-1990s in sub-tropical and tropical regions, graziers have reported that most failed to persist in established pastures. This study assessed the long-term persistence of pasture legume species with cultivars released in Australia. Forty-four old pasture evaluation sites were inspected, with an average age of 17.5 years after sowing. Thirteen legume species that had been sown at six or more sites were evaluated. Most species showed limited persistence, indicating that long-term adaptation across evironments is uncommon. Only two species were widely persistent: (1) Caatinga stylo (Stylosanthes seabrana), which persisted at 78% of sites; and (2) Desmanthus virgatus, which persisted at 68% of site. These species demonstrated broad adaption to long-term pastures. Intermediate persistence (20–50% of sites) was recorded for Desmanthus leptophyllus, butterfly pea (Clitoria ternatea), leucaena (Leucaena leucocephala), shrubby stylo (Stylosanthes scabra), fine-stem stylo (Stylosanthes guianensis var. intermedia) and lotononis (Listia bainesii), suggesting adaptation to a a narrower range of soil and climates. Other species, including burgundy bean (Macroptilium bracteatum), atro (Macroptilium atropurpureum), lucerne (Medicago sativa), Caribbean stylo (Stylosanthes hamata) and round-leaf cassia (Chamaecrista rotundifolia), persisted at few or no sites. The results show that most pasture legumes are not widely persistent in the region. Caatinga stylo and D. virgatus appear best suited to long-term pastures, while several other species may be useful in specific environments. This study highlights the importance of long-term evaluations for developing reliable recommendations for graziers.