Aeschynomene falcata (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Aeschynomene falcata (Poiret) DC.

Protologue: Prodr. 2: 322 (1825).

Family: Leguminosae

Chromosome number: 2n= unknown

Synonyms

Hedysarum falcatum Poiret (1804), H. diffusum Vellozo (1825, 1835), Aeschynomene apoloana Rusby (1910).

Vernacular names

• Jointvetch (used for all members of the genus) (En)
• Indonesia: turi rawa (Javanese)
• Philippines: torog-torog (Bikol).

Origin and geographic distribution

A. falcata is native to the higher altitude tropical or subtropical parts of Argentina, Bolivia, Brazil, Colombia, and Paraguay. It has been introduced into many South-East Asian countries and Australia.

Uses

A. falcata is used in grazed pastures and is not appropriate to cut-and-carry systems. It has been tested as a low-growing cover crop.

Properties

Nitrogen concentrations range from 1-2%, and in vitro DM digestibilities from 42-65%. Phosphorus concentrations are typically 0.1-0.2%. A. falcata is readily eaten by livestock although older stems may be rejected in favour of young grass. In the Australian cultivar "Bargoo" there are 375 seeds/g.

Botany

A prostrate, herbaceous perennial with a short tough taproot. Stems up to 1 m long and 1-3 mm diameter, puberulent, decumbent, showing little tendency to produce roots at the nodes; small nodules to about 2 mm diameter occur on both the taproot and secondary roots; older stem bases woody to 3 mm thick. Leaf 5-7(-9) foliolate; leaflet obovate-elliptical, 6-12 mm × 2.5-4 mm, pubescent. Inflorescence with usually only 1 or 2 flowers developing, longer than the subtending leaf; flower 7-10 mm long, yellow, with orbiculate standard. Pod 4-8-articulate, puberulent, slightly curved, stipe 6-14 mm long; articles 3-4 mm × 2.5-3.5 mm, the body of the articles tending to break away from the margins. Seed yellowish-brown to black, 2-2.5 mm × 1.4-1.7 mm.

"Bargoo" plants develop slowly and may take several years to reach maximum size. They flower throughout the growing season provided moisture is adequate. Pod segments open when seed is ripe. Spread of seed is assisted by passage through the grazing animal. Persistence is ensured by build-up of soil seed levels from 1000 to 8000/m², depending on management history and environment.

Ecology

A. falcata occurs naturally on rocky hillsides, in savannas, and in cultivated fields, at elevations to about 1800 m. "Bargoo" originates from 25°30'S in central Paraguay where it was growing on a rocky sandstone ridge in forest country. In eastern Australia, "Bargoo" is adapted to a variety of poor to moderately fertile soils derived from sandstone, shale and granite between 20-30°S. Most areas where "Bargoo" has proven successful have an annual rainfall between 700-1200 mm. It can tolerate temporary waterlogging and periods of drought, but grows best on moist, well-drained soils. It does not tolerate sustained wet conditions. On suitable soils it is a very persistent legume.

Agronomy

"Bargoo" is readily established from seed. Because it is often extremely hard, seed may need scarification if a high level of immediate germination is desired. Seed should be inoculated with an appropriate Bradyrhizobium strain, although effective nodulation may be achieved from native strains in some soils. Best establishment is obtained from shallow or surface sowing on a clean, well prepared seed-bed. Although tolerant of low fertility, it can respond to applications of P.

The only disease of any consequence is caused by Colletotrichum sp. which attacks the stem near the growing tip, ultimately resulting in tip death. This is a problem in humid environments, particularly in seed crops. "Bargoo" is not affected by amnemus weevil ( Amnemus quadrituberculatus ) and is resistant to rootknot nematodes ( Meloidogyne spp.)

It is extremely tolerant of, and can still produce seed under heavy grazing. "Bargoo" is too low-growing for ease of hand harvest, and is therefore grazed. Yields are generally low and may not exceed 1-2 t/ha of DM per year. "Bargoo" is not suitable for hay as leaves shed readily.

Genetic resources and breeding

A small collection, including "Bargoo", is held at ATFGRC (CSIRO, Australia). No breeding programmes are anticipated. It was tested with moderate short-term success on Sumba Island (10°S, 770 mm rainfall with a 4 month wet season) in eastern Indonesia.

Prospects

Since the only commercial cultivar ("Bargoo") originates from near the southern extremity of its natural distribution, which has only been evaluated to a limited extent globally, it is difficult to speculate on the prospects of the species. "Bargoo" should have a role in those parts of the sub-humid tropics and subtropics with heavily grazed pastures on light, infertile and well drained soils.

Literature

• Bishop, H.G., Pengelly, B.C. & Ludke, D.H., 1988. Classification and description of a collection of the legume genus Aeschynomene. Tropical Grasslands 22: 160-175.
• Hennessy, D.W. & Wilson, G.P.M., 1974. Nutritive value of Bargoo jointvetch (Aeschynomene falcata) and companion grasses when fed to sheep. Journal of the Australian Institute of Agricultural Science 38: 82-84.
• Oram, R.N., 1990. Register of Australian herbage plant cultivars. CSIRO, Australia. pp. 276-277.
• Rudd, V.E., 1955. The American species of Aeschynomene. Contributions from the United States National Herbarium 32: 88-90.
• Skerman, P.J., Cameron, D.G. & Riveros, F., 1988. Tropical forage legumes. FAO, Rome. pp. 211-212.
• Wilson, G.P.M., 1980. Bargoo jointvetch: tough legume for tough country. Agricultural Gazette of New South Wales 91: 51-53.
• Wilson, G.P.M., Jones, R.M. & Cook, B.G., 1982. Persistence of jointvetch (Aeschynomene falcata) in experimental sowings in the Australian subtropics. Tropical Grasslands 16: 155-156.

Authors

B.G. Cook