Centrosema macrocarpum Benth.
|Author: L.t Mannetje|
| Common names
Origin and geographic distribution
C. macrocarpum occurs naturally between latitudes 20°S and 20°N and is particularly frequent north of the equator from northern Brazil to Venezuela, Colombia and all Central American countries north to Mexico. It has been introduced in many tropical countries.
Perennial, taprooted vine, trailing stems with variable tendency to root at nodes. Stem pilose with greyish hairs when young, glabrescent, lignified at base. Leaves trifoliolate; stipules triangular, petioles and petiolules pubescent; leaflets broadly to narrowly ovate, apically acute to acuminate, rounded or slightly wedge-shaped at the base; central leaflet larger and longer petiolated than laterals, mostly 8-13 cm x 3-8 cm, papyraceous to subcoriaceous, almost glabrous to pubescent on lower or both surfaces; frequently with a light-green marking along midrib. Inflorescence an axillary raceme with up to 30 flowers inserted in pairs along rachis; flower subtended by a pair of ovate-lanceolate-falcate bracteoles; calyx campanulate, 5-teethed with carinal tooth considerably longer than others; petals showy and cream-coloured with purple centre; standard orbicular-emarginate, 3-6 cm in diameter, pubescent outside; wings and keel much smaller than standard. Pod linear, compressed, up to 30 cm x 1 cm, straight to slightly bent and beaked, subglabrous, containing up to 25 seeds, dehiscent. Seeds transversely oblong to rectangular, on average 5 mm x 3 mm, yellowish-brownish unicoloured, mottled or marbled (Schultze-Kraft, 1992).
C. macrocarpum is used as forage, ground cover in plantation agriculture and as green manure. It can either be grazed or cut.
C. macrocarpum provides a palatable, high-quality forage. Depending on plant age and soil fertility, N concentration in leaves ranges from 3.5-5.0% and in vitro DM digestibility from 45-70%; P concentrations are about 0.20%. There are 15-25 seeds/g.
None has been reported.
C. macrocarpum is best adapted to the humid and sub-humid tropics with annual rainfall above 1000 mm. Once established, it is quite drought-tolerant and can remain green for up to 3-4 months into the dry season. It tolerates moderate shade (Schultze-Kraft and Clements, 1990).
It grows well on a range of soils, but preferably on medium-textured soils, provided they are well drained. It has good tolerance of low soil pH, low available P and Al and Mn toxicity (Schultze-Kraft and Clements,1990).
Propagation and planting
Seed is drilled in rows or broadcast, alone (for protein banks) or simultaneously with a grass, or strip-sown into an existing sward at 3-5 kg/ha. Mechanical or acid-scarification of seed is necessary to break hardseededness (Farķa Marmol et al., 1996). Bunch grasses such as gamba grass (Andropogon gayanus Kunth) or guinea grass (Panicum maximum Jacq.) are suitable for association with C. macrocarpum; successful associations have also been obtained with Brachiaria dictyoneura (Fig. & De Not.) Stapf. (Schultze-Kraft, 1992).
C. macrocarpum has specific rhizobial strain requirements (Sylvester-Bradley, 1984).
Growth and development
C. macrocarpum is extremely photoperiod-sensitive. Flowering is induced by shortening daylength. Flowering is stimulated by removal of accumulated biomass and provision of support. Tripping of flowers, usually by large insects such as bumblebees, is required for seed-setting (Schultze-Kraft, 1992).
Diseases and pests
C. macrocarpum is one of the most disease and pests tolerant Centrosema spp.. None of the economically important diseases of the genus (Rhizoctonia foliar blight, anthracnose, Cercospora leaf-spot, and bacterial blight) has been observed to affect C. macrocarpum seriously. Leaf-eating insects can be a problem during dry periods. (Schultze-Kraft, 1992). Soybean mosaic virus infection by aphids has been reported from Colombia (Morales et al., 1990).
Depending on soil-moisture conditions, DM yields on acid, moderately fertile to infertile soils may reach up to 5 t/ha per 12 weeks; annual DM yields averaging 15 t/ha have been reported from Colombia. Seed production can reach 800 kg/ha. However, C. macrocarpum is not very tolerant to grazing (Maldonado et al., 1995; Ibrahim and t Mannetje, 1998; Avila and Urriola, 1998). Its major potential is seen in legume-only cut-and-carry systems, for protein banks and as a non-annual ley legume.
Avila M. A. and Urriola D. (1998); Ibrahim M.A. and t Mannetje L. (1998); Maldonado H. et al. (1995); Marmol J.F. et al. (1996); Morales F.J. et al. (1990); Schultze-Kraft R. (1992); Schultze-Kraft R. and Clements, R.J. (1990); Sylvester-Bradley R. (1984)
[Comments from Prof. Dr Rainer Schultze-Kraft are acknowledged]