Centrosema acutifolium (PROSEA)
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Introduction |
Centrosema acutifolium Benth.
- Protologue: Comm. legum. gen.: 54 (1837).
- Family: Leguminosae
- Chromosome number: 2n= 20?
Origin and geographic distribution
The origin of C. acutifolium is in tropical America, restricted to 4-6°N in Colombia and Venezuela, and in central-west and south-east Brazil. A cultivar and several experimental lines have been spread for testing from South America to other tropical regions, including South-East Asia.
Uses
C. acutifolium is used as forage for ruminants in grazed pastures or in cut-and-carry systems.
Properties
C. acutifolium is similar to centro ( C. pubescens Benth.) in several regards, including nutritive value. Depending on plant age, N concentrations in leaves range from 3.5-5.0%, and in vitro DM digestibility from 45-75%. Phosphorus concentrations in leaves range from 0.14-0.27%, and Ca from 0.38-1.13%. There are 15-20 seeds/g.
Description
A perennial, trailing-twining herb; stems slender, pubescent, with tendency to root at nodes. Leaves trifoliolate, young leaflets distinctly purplish; stipules deltoid-acuminate, pubescent; petioles and petiolules pubescent, reddish at their base; leaflets ovate to ovate-lanceolate, apically acuminate, membranaceous, puberulous to subglabrous on both surfaces; central leaflet symmetrical, 5-8.5 cm × 3-3.5 cm; lateral leaflets asymmetrical, 4-7.5 cm × 2.5-4 cm. Inflorescence an axillary raceme with up to 24 flowers inserted by pairs along the rachis; peduncle conspicuously long, up to 24 cm, pubescent; flower papilionaceous, subtended by a pair of short, ovate-acuminate bracteoles; calyx campanulate, 5-toothed, pilose, carinal and lateral teeth short; petals light violet; standard orbicular emarginate, 28-35 mm × 32-40 mm, pubescent outside. Pod linear, straight to slightly bent, up to 20 cm long, beaked, scabrid, containing 10-15 seeds, dehiscent. Seed cylindrical, 5-7 mm × ca. 3 mm, greenish-yellow with dark, fine mottles.
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. Seed yields are, therefore, often low, but under adequate soil-moisture conditions, seed production potential is high.
Other botanical information
C. acutifolium has only recently been rediscovered. Germplasm now known to be C. acutifolium was, until recently, frequently referred to as Centrosema sp., Centrosema sp. nov., or Centrosema new sp. No 2. 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. nud. from central-west Brazil. The species description given above refers to var. orinocense; it is represented by cultivar "Vichada" recently released in Colombia.
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.
Ecology
C. acutifolium is best adapted to sub-humid, tropical environments with 1000-2500 mm rainfall per year and a distinct dry season. It tolerates 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. C. acutifolium tolerates soil acidity and toxic levels of Al and Mn very well; its nutrient requirements are low; its shade tolerance is moderate.
Propagation and planting
C. acutifolium seed is drilled in rows or broadcast, alone or simultaneously with a grass, or strip-sown into an existing grass-sward at a rate of 3-4 kg/ha. Mechanical or acid-scarification of seed is necessary in order to overcome hard-seededness. Although it can nodulate from native cowpea rhizobia, inoculation with a Bradyrhizobium strain of known effectiveness is recommended. Grasses suitable for association with C. acutifolium are bunch grasses such as guinea grass ( Panicum maximum Jacq.) on fertile soils, or gamba grass ( Andropogon gayanus Kunth) on infertile soils. However, successful associations have also been obtained with the stoloniferous Brachiaria dictyoneura (Fig. & De Not.) Stapf.
Husbandry
Fertilization with P and K enhances establishment of C. acutifolium on most tropical soils. Despite the legume's adaptation to soils of medium to low fertility, it responds well to maintenance fertilization with these nutrients. Besides maintenance fertilization, appropriate grazing management is needed to maintain an adequate legume proportion in a C. acutifolium /grass association. Grazing must allow sufficient seedling recruitment and/or rooting from stolons to maintain plant density.
Diseases and pests
C. acutifolium shows good tolerance, mainly in sub-humid environments, to the major Centrosema diseases. It is, however, more susceptible to Pseudomonas bacterial blight than other Centrosema species. Leaf-eating insects can be a problem during dry periods.
Harvesting
The legume is usually harvested by grazing but can be cut and fed to animals. Cutting intervals will depend on soil moisture and fertility; a 10-14 week cutting interval and a 10-15 cm cutting height are suggested.
Yield
Wet-season DM yields on acid soils of low fertility range mostly between 1-3 t/ha per 12 weeks; on soils of somewhat better fertility they can be as high as 5 t/ha. Dry-season DM yields seldom reach 1 t/ha per 12 weeks. Year-round animal production can be improved considerably if it is present in a pasture. For example, in association with Andropogon gayanus , 180 kg liveweight gain per steer per year has been measured as compared with 110 kg/steer per year from A. gayanus alone. The seed production potential is high; up to 700 kg/ha can be obtained.
Genetic resources
A limited number of accessions of both C. acutifolium forms is available at CIAT (Colombia). They appear to adequately represent its natural variability.
Breeding
Some exploratory cross-compatibility studies have been conducted with C. acutifolium and closely related species such as C. pubescens and C. macrocarpum Benth. However, there is currently no programme to improve C. acutifolium through breeding.
Prospects
The main value of C. acutifolium lies in the fact that it combines the high nutritive value and drought tolerance of the closely related C. pubescens with adaptation to acid, low-fertility soils and good disease tolerance. For cut-and-carry systems, however, it is inferior to C. macrocarpum because of lower DM production.
Literature
- Instituto Colombiano Agropecuario, 1987. Centrosema "Vichada". ICA, Bogotá, Colombia. Boletín Técnico No 152. 13 pp.
- Schultze-Kraft, R., Benavides, G. & Arias, A., 1987. Recolección de germoplasma y evaluación preliminar de Centrosema acutifolium [Recollection of germplasm and preliminary evaluation of Centrosema acutifolium]. Pasturas Tropicales - Boletín 9: 12-20.
- Schultze-Kraft, R. & Clements, R.J. (Editors), 1990. Centrosema: biology, agronomy, and utilization. CIAT, Cali, Colombia. 667 pp.
Authors
R. Schultze-Kraft
