Animal Production from Legume-based Ley Pastures in Southeastern Queensland

摘要

As soils used for cropping in central and southeastern Queensland decline in organic matter and available nitrogen, the benefits of using legume-based ley pastures as an alternative to using fertiliser nitrogen are being more widely recognised. However, as well as providing increases in soil fertility for subsequent cropping cycles, ley pastures also need to provide adequate returns to farmers from livestock production. This study at Brian Pastures Research Station in southeast Queensland compared forage and animal production from eight tropical pastures, which included legumes identified in recent evaluation programs and being developed for use by farmers. The pastures used were lablab (Lablab purpureus cv. Highworth), which is an annual legume that was resown each year; Macrotyloma daltonii CPI 60303 and Vigna trilobata CPI 13671, which are annual legumes that regenerate from seed each year; butterfly pea (Clitoria ternatea cv. Milgarra) and burgundy bean (Macroptitium bracteatum CPI 27404), which are perennial legumes; a grass pasture of green panic (Panicum maximum var. trichoglume cv. Petrie), creeping bluegrass (Bothriochloa insculpta cv. Bisset) and Queensland bluegrass (Dichanthium sericeum); and the same mixture of grasses with butterfly pea and with caatinga stylo (Stylosanthes seabrana cw. Primar and Unica). End-of-season yields ranged from 1 to 5 t/ha, with lablab and the grass-legume pastures producing the highest yields. M. daltonii and V. trilobata regenerated each year, but regular spraying for weed control was necessary. Burgundy bean persisted for three years and butterfly pea was even more persistent. Both butterfly pea and Caatinga stylo persisted and combined well with the grasses. Lablab produced the most liveweight gain/ha, with growth rates from 0.60 to 0.86 kg/head/day. Growth rates on other legumes varied from 0.39 to 0.79 kg/head/day, and there were some differences in the duration of grazing. Liveweight gain/ha was similar for butterfly pea and burgundy bean and was higher than for V. trilobata, followed by M. daltonii. On the grass and grass-legume pastures, growth rates ranged from 0.39 to 0.71 kg/head/day, with legume-based pasture producing gains of 30 to 70 kg/ha more than the grass-only pasture over five years.