Centrosema acutifolium Benth.
|Author: L.t Mannetje|
|Origin and geographic
Perennial, trailing-twining herb; slender stems, pubescent, with tendency to root at
nodes. Leaves trifoliolate, young leaflets distinctly purplish; stipules
There are two morphologically and physiologically distinct forms of C. acutifolium
related to their geographical origin: (1) var. orinocense nom. nud. from a small
distribution niche in Colombia and Venezuela, and (2) var. matogrossense nom.
C. acutifolium is closely related to C. pubescens Benth. and the species are morphologically very similar. The main characteristics that distinguish C. acutifolium are: (1) the purplish colour of young leaflets, (2) the short bracteoles and calyx teeth, (3) the scabrid pod indumentum, and (4) the cylindrical seeds (Schultze-Kraft, 1992).
C. acutifolium is used as forage in grazed pastures or in cut-and-carry systems. Optimal cutting intervals depend on soil moisture and fertility; a 10-14 week cutting interval and a 10-15 cm cutting height are suggested. It is an effective understorey for timber trees and in coconut plantations with about 60 % light transmission. A cultivar 'Vichada' has been released in Colombia (Ramírez, 1987).
Depending on plant age, N concentrations in leaves range from 3.5-5.0%,
C. acutifolium is best adapted to sub-humid, tropical environments with 1000-2500 mm rainfall per year and a distinct dry season of up to 5 dry months. Var. orinocense requires well-drained, light-textured soils, whereas var. matogrossense grows particularly well on heavier soils, including those with seasonal drainage problems. Its shade tolerance is moderate (Schultze-Kraft & Clements,1990).
C. acutifolium tolerates soils of low pH and toxic levels of Al and Mn very well; its nutrient requirements are low.
Propagation and planting
C. acutifolium seed is drilled in rows or broadcast, simultaneously with a grass, or strip-sown into existing grass-swards at 3-4 kg/ha. Mechanical or acid-scarification of seed is recommended to overcome hard-seededness. C. acutifolium can be grown in association with bunch grasses such as guinea grass (Panicum maximum Jacq.) on fertile soils, or gamba grass (Andropogon gayanus Kunth) on infertile soils. Successful associations have also been obtained with the stoloniferous Brachiaria dictyoneura (Fig. & De Not.) Stapf. (Schultze-Kraft, 1992).
Although it can nodulate effectively from native cowpea rhizobia (Tang et al., 1994) inoculation with a rhizobial strain of known effectiveness is recommended.
Growth and development
C. acutifolium flowers late in the season, and this can reduce seed production
in years with an early onset of the dry season. As a result, seed yields are often low,
Diseases and pests
C. acutifolium shows good tolerance to the major centrosema diseases in
sub-humid environments. It is, however, more susceptible to Pseudomonas bacterial
Wet-season DM yields on acid soils of low fertility can be as high as 3 t/ha per 12 weeks; on soils of somewhat better fertility they can reach 5 t/ha. Dry-season DM yields seldom exceed 1 t/ha per 12 weeks. C. acutifolium was more productive and persistent than the other Centrosema spp., regardless of companion grass, and this was associated with higher liveweight gains, particularly during the dry season (Lascano et al. 1989). In association with gamba grass, 180 kg liveweight gain per steer per year has been measured as compared with 110 kg/steer per year from gamba grass alone. Milk yield in association with gamba grass was increased 15% (1.2 kg) compared to grass alone (Lascano and Avila, 1991). For cut-and-carry systems, however, it is inferior to C. macrocarpum because of lower DM production. The seed production potential is high; yields up to 700 kg/ha can be obtained.
Diulgheroff S. et al. (1990); Lascano C. E. and Avila P. (1991); Lascano C. et al. (1989); Ramirez P. A. (1987); Schultze-Kraft R. (1992); Schultze-Kraft R. and Clements R.J. (Eds) (1990); Tang M. et al, (1994)
[Comments from Prof. Dr Rainer Schultze-Kraft are acknowledged]