Crotalaria micans (PROSEA)
Crotalaria micans Link
- Protologue: Enum. pl. hort. berol. 2: 228 (1822).
- Family: Leguminosae - Papilionoideae
- Chromosome number: 2n= 16
Crotalaria anagyroides Kunth (1824).
- Caracas rattlebox (Am)
- Thailand: hinghai
- Vietnam: sục sạc cao, sục sạc soc.
Origin and geographic distribution
C. micans originated from Central and South America. It has been introduced into many tropical and subtropical countries, including those in Malesia, where it also naturalized locally.
In Central and South America, Indo-China, Indonesia, Malaysia, and Sri Lanka, C. micans is grown as a green manure and cover crop, for instance in plantations of coffee, tea, tobacco and rice. Young shoots and leaves are used as fodder for cattle. It is widely grown as an ornamental.
Unlike many other Crotalaria spp., C. micans is reported to be highly palatable and non-toxic to cattle. Young vegetative material contains per 100 g dry matter: crude protein 23 g, crude fibre 28 g, ash 7.2 g, ether extract 2.2 g, non-fibre extract 39.6 g, Ca 0.57 g, P 0.28 g. Tests in Colombia indicated per 100 g dry matter: N 3.6 g, K 2.0 g, Ca 2.1 g, Mg 0.3 g.
The weight of 1000 seeds is 18 g.
- Shrub up to 4 m tall; young branches angular, appressed pubescent.
- Leaves trifoliolate; petiole 3-5 cm long, longitudinally grooved above; stipules linear, 0.5-7 mm long, caducous; leaflets oblong-lanceolate to narrowly elliptic, 4-10 cm × 1-4.5 cm, apex acute to acuminate or obtuse, base cuneate, lower surface and midrib above puberulous, upper surface glabrous, lateral leaflets slightly smaller than the terminal one.
- Inflorescence a rather dense, 15-30-flowered raceme, 15-30 cm long, terminal, often leaf opposed; bracts linear, about 1 cm long, very early caducous; pedicel 5-9 mm long; bracteoles similar to bracts but smaller, very early caducous, inserted just above the middle part of the pedicel.
- Flowers bisexual, 5-merous; calyx 8-13 mm long, appressed puberulous, tube campanulate, 5-6 mm long, bilabiate and 5-lobed, lobes longer than the tube, upper lobes triangular-acuminate, often coherent at the tips with the lateral lobes and woolly on the inside of the margins; corolla 14-18 mm long, yellow, purplish-veined; standard ovate-circular to slightly reniform, 13-14 mm × 18-21 mm, glabrous; wings oblong, 12-15 mm long, claws 3-4 mm long; keel 13-15 mm long, abruptly rounded a little below the middle, with a slightly incurved, untwisted beak; stamens 10, monadelphous, anthers dimorphic, 5 anthers basifixed, with filaments 3-6.5 mm long, 5 anthers dorsifixed, with filaments 4-9.5 mm long; style 8-11 mm long, curved, persistent, pubescent.
- Fruit an inflated, short-stipitate pod, subcylindrical, 3-4 cm × 1 cm, appressed puberulous, brown, dehiscent, with 16-20 seeds.
- Seed unequal-sided heart-shaped, about 4.5 mm × 3.5 mm, fine papillate, yellowish-brown.
Early growth of C. micans is fast, giving it a competitive advantage over most weeds. It can cover the soil in 3 weeks after germination and may reach 2.5 m after 3 months and 3.5 m after 6 months. In Bogor, Indonesia, the first seeds mature 7 months after sowing. C. micans forms root nodules with Bradyrhizobium spp. and fixes nitrogen.
C. micans is characterized by terminal inflorescences on which the large flowers are grouped tightly with prominent, long curled bracts and bracteoles.
C. micans is tolerant of a wide range of climatic and soil conditions. It grows best in lowland areas, but is generally grown up to 1600 m altitude. In Java, it is found up to 1800 m altitude, and in Colombia even as high as 2600 m. Full sunlight is required for good seed production. Seed production is poor at high elevations.
C. micans is propagated by seed. When broadcast, a seed rate of 20-35 kg/ha is used; 6-12 kg/ha is adequate for sowing rows 0.9-1.5 m apart. In Java it is sown at the onset of the drier season in May-June. In established tea plantations it is sown immediately after pruning. Once established it will reseed itself.
In Java fungal diseases are reported caused by the fungi Corticium salmonicolor and Sclerotium rolfsii . The dadap fungus (Septobasidium bogoriense), which also affects Erythrina spp. grown as shade trees, grows on the base of the stem, making it susceptible to other diseases. C. micans is a host of Lasiodiplodia theobromae affecting both cocoa and tea. The crotalaria bug (Ragmus importunatas) living on the underside of leaves and on the tips of branches causes leaves to turn yellow. The damage can be so serious that the cover crop has to be removed. It also attacks several Asian Crotalaria spp., but not C. pallida Aiton or C. trichotoma Bojer.
C. micans can be cut repeatedly, provided it is not cut too low and a few leaves per stem are left. It is easily incorporated into the soil as the lower stem does not start to lignify until 4 months after planting. Decomposition is rapid: in tests in Colombia, 40% of a crop was decomposed after 1 month and 60% after 2 months. However, in tea plantations in Java it is recommended to incorporate it into the soil 6 weeks before tea is planted.
From Java, yields of 40 t/ha fresh material 4 months after planting are reported, containing about 150 kg nitrogen, while in the southern United States, 6 months after planting 4.5 t/ha dry matter containing 100 kg nitrogen has been reached.
Genetic resources and breeding
A germplasm collection of Crotalaria L. is being maintained by the United States Department of Agriculture, including material of C. micans. It is unlikely that any substantial breeding programme exists.
C. micans is a useful multipurpose crop that can be grown for erosion control and for either green manure or fodder.
- Backer, C.A. & van Slooten, D.F., 1924. Geïllustreerd handboek der Javaansche theeonkruiden en hunne beteekenis voor de cultuur [Illustrated handbook of weeds of Javanese tea plantations and their significance for tea-growing]. Ruygrok, Batavia, Dutch East Indies. 128, 128a.
- Godefroy, J., 1988. Observations de l'enracinement du stylosanthes, de la crotalaire et de flemingia dans un sol volcanique du Cameroun [Observations on the rooting of Stylosanthes, Crotalaria and Flemingia in a volcanic soil in Cameroon]. Fruits 43: 79-86.
- Niyomdham, C., 1978. A revision of the genus Crotalaria Linn. (Papilionaceae) in Thailand. Thai Forest Bulletin (Botany) 11: 105-181.
- Polhill, R.M., 1982. Crotalaria in Africa and Madagascar. Balkema, Rotterdam, the Netherlands. p. 371.
- Suarez-Vasquez, S. & Carillo-Pachon, I.F., 1976. Descomposición biológica de leguminosas y otros materiales de la zona cafetera Colombiano [Biological decomposition of legumes and other plant materials from the Colombian coffee area]. Cenicafé 27: 67-77.
- Windler, D.R. & McLaughlin, L., 1980. Crotalaria. In: Dwyer, J.D. et al. (Editors): Flora of Panama, Part 5, fasc. 5.2, Family 83: Leguminosae. Annals of the Missouri Botanical Garden 67: 606-607.