PERSISTENCE AND PRODUCTIVITY OF TROPICAL PASTURE LEGUMES ON 3 CRACKING CLAY SOILS (VERTISOLS) IN NORTH-EASTERN QUEENSLAND

There are few commercial legumes available for sowing on the cracking clay soils of north-eastern Queensland, where legumes are needed to improve quality of perennial native grass pastures and to arrest nitrogen decline in cropping land. To evaluate introduced legumes from heavy-textured soils, a replicated row experiment was established in 3 environments to assess the adaptation of 56 accessions from 37 species (22 genera). The sites were on 3 dark cracking clay soils supporting the following grasslands: Dichanthium-Bothriochloa-Astrebla; Dichanthium aristatum; and Cenchrus ciliaris on cleared Acacia harpophylla (brigalow) country. The main selection criteria during the 4-year evaluation were persistence, regeneration, production, and spread, with green leaf retention, nutrient concentrations, and pest susceptibility also being considered. The perennial legumes Clitoria ternatea (CPI 47187 and CPI 49963), Desmanthus virgatus (CPI 78373), Leucaena leucocephala (CPI 61227 and cv. Cunningham), Stylosanthes scabra (CPI 55868), and Indigofera schimperi (CPI 69495), and annuals Centrosema pascuorum (CPI 55697), Desmodium dichotomum (CPI 47186), and Vigna trilobata (CPI 47510), showed promise as pasture or short-term ley species for these clay soils (Vertisols) in subcoastal, north-eastern Queensland. Other species were identified that require evaluation of a wider range of genetic material. The role of perennial and annual sown legumes in pasture and cropping systems on these cracking clay soils is discussed.