Vigna parkeri (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Vigna parkeri Baker

Protologue: Journ. Bot. 20: 69 (1882).

Family: Leguminosae

Chromosome number: 2n= 22

Synonyms

Dolichos maranguënsis Taub. (1892), Vigna maranguënsis (Taub.) Harms (1915), V. gracilis sensu auctt., non (Guill. & Perr.) Hook.f.

Vernacular names

• Creeping vigna (Papua New Guinea) (En)
• Philippines: balatong (Bontok), bulligan (Ifugao).

Origin and geographic distribution

Creeping vigna is native to tropical East and Central Africa, but has been recorded most frequently in Kenya, Uganda and Tanzania. It is being sown in the humid subtropics in Australia and Florida (United States) and has become naturalized in the highlands of Papua New Guinea.

Uses

While the main use of creeping vigna is as a pasture legume, it is also proving useful in Papua New Guinea as a protein supplement for pigs, and as a green manure and cover crop in shifting cultivation.

Properties

Creeping vigna provides quality forage. In one report, leaves comprised 65% of the top growth and had a N concentration of 4.1% and DM digestibility of 61%, while stems had a N concentration of 2% and DM digestibility of 55%. It is generally readily eaten by cattle but there is some doubt about its acceptance by goats.

Botany

A perennial twining or prostrate stoloniferous herb. Stolons remain appressed to the soil surface, while the primary axis, and laterals developing from stolon nodes, have a twining habit. Taproot slender, freely nodulating; nodal roots at first fibrous becoming small taproots as new crowns develop. Stems slender, sparsely to densely covered with mostly spreading hairs. Leaves trifoliolate; leaflets round, ovate to ovate-lanceolate, 1-9 cm × 1-5 cm, rounded to acuminate at the apex and rounded to subacute at the base, pubescent on both faces, margins entire and densely ciliate; petiole 1-8.5 cm long; stipules lanceolate, up to 8 mm long, bilobed at the base, persistent. Inflorescence axillary, with 2-5(-10) flowers per raceme; peduncle 2-13 cm long; flowers blue, yellow or white, occurring in alternate pairs inserted on either side of a glandular node; standard oblate, 5-8(-12) mm × 5-8(-10) mm, glabrous. Pod linear-oblong, compressed, mostly 1-2(-3) cm × 4.5-5.5 mm, 2-5-seeded. Seed oblong-ovoid, 3-4 mm × 2-3 mm × 2 mm, grey-to-brown/black mottled.

Three subspecies have beeen distinguished: ssp. parkeri (flowers blue or rose, leaflets ovate, only on Madagascar); ssp. acutifolia Verdc. (flowers mainly yellow, leaflets elliptical or ovate, in Kenya, Tanzania, Mozambique); and ssp. maranguënsis (Taub.) Verdc. (flowers mainly blue or purple, leaflets round, in East and Central Africa). The occurrence of many intermediate forms makes the subdivision unpractical.

One introduction of creeping vigna which became naturalized in parts of south-east Queensland has been released as cultivar "Shaw" and is now being planted in other parts of the humid subtropics and the tropical highlands. It appears that only one form (of ssp. maranguënsis ) was introduced from Africa into Papua New Guinea at Aiyura in the Eastern Highlands about 1958, from where it has spread to the Southern Highlands, Western Highlands and Enga Provinces.

The ecotype from Papua New Guinea and "Shaw" are distinguishable by the more acuminate, often paler leaflets and the stronger twining tendency in the former. Both have blue flowers and a pale crescent on the leaflets of some plants. In south-eastern Queensland, latitude 26°S, some types flower throughout the growing season, while others, including the Papua New Guinea ecotype and "Shaw" do not flower until about May. The Papua New Guinea ecotype flowers throughout the year in its naturalized habitat in the highlands between 5°and 7°15'S.

Ecology

In general, creeping vigna has similar environmental requirements as greenleaf desmodium ( Desmodium intortum (Miller) Urban). The Papua New Guinea ecotype and "Shaw", both of which have uncertain origins, are adapted to moist soils in the high altitude tropics and low altitude subtropics where annual rainfall exceeds 1100 mm per year. They appear to grow best at cooler temperatures, and when cut by frost, mostly recover from crowns. They are tolerant of poorly fertile, acid soils (down to pH(H₂O) 5.0), and although both are also tolerant of low available soil P, have responded to applied P. They cannot withstand prolonged dry periods, but in the event of stand loss through drought, they can regenerate from the often high levels of soil seed, measured at 50 seeds/m²under close grazing to over 1000 seeds/m²under lenient grazing. Both possess moderate shade tolerance. It can spread through dense grasses such as Pennisetum clandestinum Hochst. ex Chiov. by stolons, sometimes at over 1 m/year. It may be spread over considerable distances through ingested seed being voided in the dung.

Agronomy

High levels of hard seed have been recorded and, where immediate germination is required, seed may need to be scarified. This can be achieved using mild abrasion or hot water (preliminary results suggest 10 minutes at 70 °C). Seed is best sown at 2 kg/ha into a clean, well prepared seed-bed. It may be sown on the surface or at shallow depth. Subsequent rolling improves establishment. Native cowpea rhizobia give effective nodulation. Renovation of old stands can be achieved through limited cultivation, using soil seed reserves. Where seed is unavailable or more rapid establishment is required, creeping vigna may be established from rooted stolons.

Creeping vigna is adapted to both lenient and heavy grazing. However, to achieve maximum benefit as a forage and for N fixation, stands should be maintained between 20 and 50 cm. In low-fertility soils, nutrient deficiencies should be corrected, paying special attention to P and Mo.

In Papua New Guinea, no major disease or pest problems have been recorded. A fungus ( Sclerotium rolfsii ) and a root-knot nematode ( Meloidogyne javanica ) have caused some damage in "Shaw" swards in Queensland, but had no lasting effect. Two other fungi, Rhizoctonia solani and Colletotrichum truncatum have been isolated from leaf and stem lesions in seed crops of "Shaw", but can be largely controlled by avoiding accumulation of a bulk of mature top growth.

Creeping vigna is usually grazed since its prostrate, low twining growth habit does not readily lend itself to a cut-and-carry system. High quality hay can be made from creeping vigna, but weather conditions in its preferred habitats are rarely ideal for hay-making. Improved utilization by cattle of grasses such as Pennisetum clandestinum, Axonopus affinis A. Chase and even Imperata cylindrica (L.) Raeuschel has been observed where they are associated with this legume.

No yield data are available from South-East Asia, but in Queensland, autumn presentation DM yields of 1650 kg/ha of "Shaw" were obtained from a grass/legume pasture stocked at 1.5 beast/ha.

Genetic resources and breeding

A limited range of germplasm material is held at ATFGRC (CSIRO, Australia). The species is only adapted to humid highland areas in South-East Asia and has not attracted and does not warrant breeding work, at least not until wild types have been fully exploited.

Prospects

Creeping vigna is a useful species, especially in acid soil areas where sward-forming grasses are common and in which pastures are subjected to heavy grazing. At this stage, its potential has only been partly realized. Evaluation of existing collections in tropical highland and subtropical lowland areas in South-East Asia is required.

Literature

• Cook, B.G. & Jones, R.M., 1987. Persistent new legumes for intensive grazing. 1. Shaw creeping vigna. Queensland Agricultural Journal 113: 89-91.
• Gillett, J.B., Polhill, R.M. & Verdcourt, B. 1971. Papilionoideae (2). In: Milne-Redhead, E. & Polhill, R.M. (Editors): Flora of tropical East Africa. Leguminosae 4 - Papilionoideae 2. Crown Agents for Oversea Governments and Administrations, London. pp. 635-637.
• Jones, R.M. & Clements, R.J. 1987. Persistence and productivity of Centrosema virginianum and Vigna parkeri cv. Shaw under grazing on the coastal lowlands of South-East Queensland. Tropical Grasslands 21: 55-64.
• Oram, R.N., 1990. Register of Australian herbage plant cultivars. CSIRO, Australia. pp. 269-270.
• Pentney, C.J., Whiteman, P.C., & Sivasupiramaniam, S. 1984. Studies on the germination, phenology and Rhizobium requirements of Vigna parkeri. Tropical Grasslands 18: 66-74.
• Verdcourt, B. 1979. A manual of New Guinea legumes. Botany Bulletin Number 11. Office of Forests, Division of Botany, Lae, Papua New Guinea. pp. 522-523.

Authors

B.G. Cook & A.K. Benjamin