Centrosema pubescens (PROSEA)
Centrosema pubescens Benth.
- Protologue: Comm. legum. gen.: 55 (1837).
- Family: Leguminosae - Papilionoideae
- Chromosome number: 2n= 22
Centrosema molle Martius ex Benth. (1837).
- Centro, butterfly pea (En). Flor de conchitas (Am)
- Indonesia: sentro
- Philippines: dilang-butiki (Tagalog), lesu-kesu (Subanun)
- Thailand: thua-lai, thua-sentro
- Vietnam: day trung châu lông.
Origin and geographic distribution
Originating in South and Central America, centro is now one of the most widely distributed of all legumes in the humid tropics. Centro was introduced to South-East Asia from tropical America in the 19th Century or earlier. It occurs naturalized in lowland Java.
In 1922 centro was discovered in a heavily shaded rubber plantation in Central Java, and was quickly adopted as a green manure and ground cover in plantation crops in Java, Sumatra, Peninsular Malaysia and Sri Lanka. Since the 1950s, centro has been widely used as a plantation cover and pasture legume in South-East Asia, the Pacific Islands, the wet tropics of Australia and indeed much of the humid tropics worldwide.
Centro is an efficient fixer of atmospheric nitrogen, with N concentrations generally ranging from 2.4-2.7(-3.2)%. The amount of nutrients temporarily immobilized in a centro cover can be high. Under intensively managed, well fertilized oil palm on a marine clay soil in Selangor, Malaysia, a centro cover produced 13.3 t/ha dry matter 20 months after planting, of which 5.4 t/ha was living biomass and 7.9 t/ha was litter. The nutrient content of the living biomass was per 100 g dry matter: N 2.51 g, P 0.17 g, K 1.92 g, Mg 0.23 g. Per 100 g dry matter the litter contained: N 3.18 g, P 0.12 g, K 0.36 g, Mg 0.38 g. Under comparable conditions on a sandstone-derived soil in Serdang, Malaysia, the production 12 months after planting was 4.5 t/ha living biomass and 6.7 t/ha litter, containing per 100 g dry matter of living biomass: N 3.06 g, P 0.51 g, K 2.07 g, Mg 0.14 g and of litter: N 2.34 g, P 0.44 g, K 0.35 g, Mg 0.11 g. Centro is one of the most palatable tropical legumes.
The weight of 1000 seeds is about 25 g.
A vigorous, climbing, perennial herb; trailing runners have a tendency to root at the nodes if soil moisture is high, giving it a stoloniferous appearance; roots penetrating deeply; development of taproot and lateral roots is almost equal, although soil type exerts some influence. Stems leafy, arising from the main runners at 0.5-1.5 m intervals, climbing rather than trailing, slightly hairy, possibly becoming woody when older than 18 months. Leaves trifoliolate; leaflets elliptical, ovate-oblong or ovate-lanceolate, 1-7 cm × 0.5-4.5 cm, rounded at the base, rounded to sharp-acuminate at the apex, dark green, slightly hairy, especially on the lower surface; petiole up to 5.5 cm long, stipules 2-4 mm long, persistent. Flower cleistogamous, large, pale mauve with purple lines in the centre, borne in axillary racemes, 3-5 per raceme, subtended by 2 striate bracteoles; calyx tube campanulate, teeth unequal, 2 upper ones ovate-triangular 1.5-3 mm long; standard rounded, up to 3 cm in diameter, hairy on the outside, bright or pale lilac on either side of a median greenish-yellow band with numerous dark violet stripes or blotches. Pod linear, 4-17 cm × 6-7 mm, flattened, margins prominent, straight or slightly twisted, acuminate, dark brown when ripe, containing up to 20 seeds. Seed shortly oblongoid to squarish with rounded corners, 4-5 mm × 3-4 mm × 2 mm, brownish-black, with mottled darker blotches.
Growth and development
Centro is notoriously slow to establish and requires good conditions and regular weeding during the establishment period, but when grown in a pure sward it forms a dense, compact cover 35-45 cm deep, 4-8 months after sowing. In mixtures it becomes fully established and vigorous by at least the 2nd year. In ungrazed mixtures with Guinea grass ( Panicum maximum Jacq.) it forms an impenetrable vine canopy some 2 m high. In the commonly planted mixture with calopo ( Calopogonium mucunoides Desv.) and tropical kudzu ( Pueraria phaseoloides (Roxb.) Benth.) centro persists longest under the closing canopy of plantation crops and is comparable in persistence to Calopogonium caeruleum (Benth.) Sauv. In Australia common centro flowers in April and October, with main seed harvesting periods in June-July and November-December. Cultivar "Belalto" flowers in June and has a main seed harvesting period in early August. Nodulation occurs with a range of rhizobia but optimal growth has been achieved with very few strains. Inoculation with an effective strain of Bradyrhizobium is therefore recommended. Estimates of atmospheric nitrogen fixation range from 120-270 kg/ha per year.
Other botanical information
Commercially grown forms of C. pubescens represent only a small fraction of its diversity, and any statement on the commercial forms does not necessarily pertain to the species as a whole.
Two lines of centro are in commercial use: common centro and cultivar "Belalto". "Belalto" is now identified as C. schiedeanum (comb. ined., syn.: Clitoria schiedeana Schlecht.) rather than as C. pubescens as was listed originally. It was selected by the Queensland Department of Primary Industries as an improvement over common centro because of its superior cool season growth, greater tolerance of pests and diseases, and its stronger stoloniferous growth. Its origin is Costa Rica.
Centro is cultivated in the humid tropics up to an altitude of 600(-900) m. It prefers an annual rainfall of 1500 mm or more, but is also tolerant of lower rainfall, having persisted in pastures in Africa receiving an average annual rainfall of 800 mm. Centro tolerates some waterlogging when grazing is lenient and it will survive a dry season of 3-4 months, but is not adapted to prolonged drought. It is intolerant of low temperatures; growth is noticeably reduced when temperatures fall below 20 °C and poor below 15 °C. Frost of -3 °C causes substantial leaf death, but plants may regrow from sheltered growing points near the ground. Centro is one of the shade-tolerant legumes and can persist under 80% shade. It will grow on a range of soils from sandy loams to clays. Acceptable growth may be obtained on relatively acid soils, provided extractable aluminium is less than 0.2 meq per 100 g soil. The pH range tolerated is about 4.5-8.0, but nodulation is poor towards the extremes of the range, the optimum pH being 5.5-6.0. Although centro is fairly tolerant of high Mn levels in the soil, low-pH-related Mn toxicity has been observed in acid soils, though this can be corrected by liming.
Centro combines well with other species in ground covers or mixed pastures under plantation crops. In the humid tropics the preferred legumes for fertile and infertile soils have traditionally been centro and stylo ( Stylosanthes guianensis (Aublet) Swartz) respectively. However, when soil mineral deficiencies are corrected and seed is inoculated with an effective Bradyrhizobium , centro has been more productive than stylo on all land classes.
Propagation and planting
Centro is propagated by seed. Hand-harvested seed has a high proportion of hard seed (up to 60%) and mechanical scarification is required. Seed rate is about 5 kg/ha. Since centro is somewhat slow to establish, careful seed-bed preparation and planting procedures are recommended. However, centro has been successfully sod-seeded directly into a run-down grass pasture, following heavy grazing and low slashing of the residual grass.
When planted as a component of a soil cover in oil palm or rubber plantations, centro will persist for 3-6 years until the tree canopy closes. It contributes considerably to the nitrogen nutrition of trees. In an experiment in Malaysia comparing centro with grasses as cover crop under oil palm, the N levels of oil palm leaves were about 10% higher with centro than with grasses. Observations in northern Queensland showed that levels of soil N in regularly grazed, unfertilized mixed pastures of centro and Guinea grass hardly declined over a period of 16 years. Properly fertilized and carefully grazed grass/centro associations have been persistent, productive and competitive against weeds and timber regrowth. In mixtures with grasses, notably Guinea grass, centro tolerates rotational or continuous grazing, but in pure stands it is intolerant of grazing. Under acidic soil conditions, centro is more responsive to Mo, Ca, K and P than tropical kudzu which, in turn, is more responsive than stylo. Centro is more sensitive than stylo to soil P deficiency but is less sensitive to Cu and possibly S deficiencies.
Bioassays conducted in Taiwan revealed that banana growth is affected by phytotoxins from interplanted centro. The phenolic compound p-hydroxybenzoic acid in centro caused a growth inhibition similar to that produced by rhizosphere or plant extracts.
Diseases and pests
Centro is relatively free of major diseases and pests, although some virus and bacterial diseases have been noted from time to time and seasonal infestations of Cercospora leaf spot and red spider mite ( Tetranychus sp.) have been reported. In the humid tropics it is noticeable that the infestation of foliar blight ( Rhizoctonia solani ) may cause some dieback and that the attack of ladybird beetles (e.g. Epilachna indica ) may affect plant growth and even cause complete defoliation. The damage can be severe when centro is grown in a pure sward, especially during the wet season. However, none of these have warranted commercial control measures.
Centro has persisted for decades as plantation cover or in well-managed grazed associations with grasses, but it has not been very stable in cut-and-carry systems. When used as fodder centro is usually grazed, or it can be cut for stall feeding. It can be selectively overgrazed unless care is taken. Centro is usually consumed fresh but it can be ensiled or dried for hay or pellets.
Biomass production of cover crops is rarely measured. Pure stands of centro have produced annual dry matter yields of up to 12 t/ha. In mixed pastures this is more likely to be about 3-4 t/ha per year. Standing dry matter yield of centro in grazed mixed pastures is unlikely to exceed 1 t/ha. Well managed grass/centro pastures have consistently supported stocking rates of 4 steers (of 250 kg liveweight) in the Malaysian wet tropics, producing about 500 kg/ha of liveweight gain per year. Seed production can reach more than 200 kg/ha.
Seed of centro has been sold for many decades in South-East Asia and other humid tropical areas. Large germplasm collections are held by the Australian Tropical Forage Genetic Resource Centre (ATFGRC, Australia), the Centro Nacional de Recursos Genéticos/Empresa Brasileira de Pesquisa Agropecuária (CENARGEN/EMBRAPA, Brazil) and the Centro Internacional de Agricultura Tropical (CIAT, Colombia).
Plant breeding programmes have been undertaken and improved cultivars have been released by the Queensland Department of Primary Industries (QDPI) and the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Australia and CIAT in Colombia. However, the most promising lines are beginning to emerge from plant collections in South and Central America.
Centro will continue to be an important component of cover crop mixtures for plantation crops, although its role as shade-tolerant component has been partly taken over by Calopogonium caeruleum . Centro is also a recommended legume in the "Three Strata Forage System" in Bali, Indonesia. Except for the humid tropics of Australia and a few areas of Malaysia and the Philippines, the potential of centro as a component of grazed pastures has been largely unrealized.
- Clements, R.J., Williams, R.J., Grof, B. & Hacker, J.B., 1983. Centrosema. In: Burt, R.L., Rotar, P.P., Walker, J.L. & Silvey, M.W. (Editors): The role of Centrosema, Desmodium, and Stylosanthes in improving tropical pastures. Westview Press, Boulder, Colorado, United States. pp. 69-96.
- Han, K.J. & Chew, P.S., 1982. Growth and nutrient content of leguminous covers in oil palm plantations in Malaysia. In: Pusharajah, E. & Chew, P.S. (Editors): The oil palm in agriculture in the eighties. Vol. 2. The Incorporated Society of Planters, Kuala Lumpur, Malaysia. pp. 235-251.
- Nitis, I.M., Lana, K., Suarna, M., Sukanten, W., Putra, S. & Arga, W., 1989. Three strata system for cattle feeds and feeding in dryland farming area in Bali. Final report to the International Development Research Centre, Ottawa, Canada. 252 pp.
- Schultze-Kraft, R. & Clements, R.J. (Editors), 1990. Centrosema: biology, agronomy and utilisation. Centro Internacional de Agricultura Tropical, Cali, Colombia. 667 pp.
- Skerman, P.J., Cameron, D.G. & Riveros, F., 1988. Tropical forage legumes. Food and Agriculture Organization, Rome, Italy. pp. 243-255.
- Teitzel, J.K. & Burt, R.L., 1976. Centrosema pubescens in Australia. Tropical Grasslands 10: 5-14.
J.K. Teitzel & Chen Chin Peng