Tropical Grasslands (2006) Volume 40, 24–32

A survey of the use of lucerne, butterfly pea and lablab in ley pastures in the mixed-farming systems of northern Australia

B.R. CULLEN AND J.O. HILL

CSIRO Sustainable Ecosystems, Brisbane, Queensland, Australia

Abstract

A farmer and paddock survey of ley pastures was conducted across the northern mixed-farming region to identify producers’ attitudes to, and expectations of, ley legume pastures, the persistence of perennial legume species and the build-up of soil carbon (C) under ley pastures. Six butterfly pea (Clitoria ternatea) growers in central Queensland, 8 lucerne (Medicago sativa) growers in southern Queensland/northern New South Wales and 6 lablab (Lablab purpureus) growers (across both regions) were surveyed. The species played different roles in farming systems. Lablab was used as a short-term pasture to build soil fertility in crop rotation. Lucerne was used as a phase pasture (3–5 years) in cropping systems, while butterfly pea was often established as a permanent or semi-permanent pasture. In general, the persistence attributes of the perennial legumes fitted well with how producers used them; butterfly pea pastures persisted for up to 10 years, while lucerne plant densities declined to low numbers within 5 years. Differences in soil C between ley pasture and continuously cropped areas nearby ranged from −29 to 101%. Pasture age was the most important factor in explaining the change in soil C, older pasture leading to greater build-up of soil C. The level of soil phosphorus and percentage of grass in the sward were positively correlated with increasing soil C in the pasture phase.

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