Crotalaria trichotoma (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Crotalaria trichotoma Bojer

Protologue: Ann. sc. nat. Series 2. Vol. 4: 265 (1835).

Family: Leguminosae - Papilionoideae

Chromosome number: 2n= 16

Synonyms

• Crotalaria zanzibarica Benth. (1843),
• C. usaramoensis Baker f. (1914).

Vernacular names

• Curare pea (En). West Indian rattlebox (Am)
• Indonesia: geger sore (Sundanese).

Origin and geographic distribution

C. trichotoma originates from the coastal regions of Tanzania and northern Mozambique. It was introduced into Java in 1916 by the Botanic Garden in Bogor. It was soon taken into cultivation and spread through Java and Sumatra, where it occasionally escapes from cultivation, but does not seem to naturalize. It is now distributed throughout the humid tropics and sometimes naturalizes (e.g. in Taiwan and Vietnam).

Uses

Because of its quick growth and good production of green matter C. trichotoma is grown as a green manure and cover crop in tea, coffee, rubber and citrus plantations. It is especially grown in locations where C. micans Link is severely attacked by Ragmus bugs or where a lower-growing cover is preferred. In Indonesia it has been tested as an intercrop in maize and as a green manure crop in vegetables. In Argentina, Central America and Angola it is grown for fodder, often in mixed swards with grasses.

Properties

The leaves and stems are very nutritious and are readily eaten by cattle and horses. Although poisonous alkaloids have been found in many other Crotalaria spp., C. trichotoma appears to be free of them. Its bark contains fibre, but this is of poor quality, unsuitable for making bags, possibly adequate for cordage.

Botany

• Erect annual or short-lived perennial herb, up to 2.7 m tall, deep rooted, base often woody, upper part of stem well branched. Stem ribbed, appressed puberulous.
• Leaves trifoliolate, without stipules; petiole 2-5 cm long; leaflets lanceolate to elliptical-oblong, 4-14 cm × 1-4 cm, base acuminate, apex acute or rounded, glabrous or rarely puberulous above, appressed puberulous below.
• Inflorescence a terminal raceme, 30-40(-90) cm long; flowers many, closely arranged; pedicel 4-8 mm long; bracts linear-caudate, 2-4 mm long; bracteoles inserted at the base of the calyx or rarely on upper part of pedicel, linear, 1-1.5(-2.5) mm long.
• Calyx becoming truncate at base and deflexed against the pedicel, 4-6 mm long, glabrous or thinly appressed puberulous, the 5 lobes reduced to small, widely spaced teeth; standard obovate-elliptical or suborbicular, 10-13 mm wide, yellow, reddish-purple veined, glabrous outside; wings and keel about equal in size, wings with a dark mask at the base, keel 12-13 mm long, rounded about the middle, with a slightly incurved, sharp, untwisted beak; stamens 10, all joined, sheath open at least at the base, anthers dimorphic, 5 large ones alternating with 5 short ones; ovary stipitate.
• Pod shortly stipitate, subcylindrical, inflated, (30-)35-45 mm × 7-11 mm, black when ripe, appressed puberulous, 50-70-seeded.
• Seed obliquely heart-shaped, 2-3 mm long, smooth, orange-buff or terracotta.

C. trichotoma is self-incompatible and tests indicate that its flowers are pollinated by insects before they open, suggesting that it is cleistogamous and self-compatible. In the literature C. trichotoma is better known by its synonymous names. It resembles C. pallida Aiton, in which the wings are shorter than the keel and lack the basal dark colouration.

Ecology

The natural habitat of C. trichotoma is grassy sites in coastal forest clearings, bushland, Brachystegia woodland, grasslands, roadsides and cultivated fields, up to an altitude of 1800 m. In Java and Sri Lanka it is cultivated up to 1500 m altitude. On degraded and compacted soils it performs better than most other green manure crops. It is fairly tolerant of drought.

Agronomy

C. trichotoma is propagated by seed. Direct sowing at a rate of 2.5-3.5 kg/ha in strips about 0.3-1 m apart is most common. Sowing should not be done under very wet conditions. Two weedings are generally required before it covers the ground, which occurs after 3-4 months. Once established, C. trichotoma propagates abundantly by self-seeding. It produces a large amount of green matter but is rather short-lived and does not tolerate frequent heavy lopping. Cutting should be done at a height of 45-60 cm above the ground, always leaving a few leaves. Cutting at lower levels results in very poor regrowth. Green manure yields are generally slightly lower than from C. micans; a yield of 5 t/ha, obtained 5 weeks after a previous harvest is reported from Bogor. A soil cover may contain about 25 t/ha fresh organic matter 6 months after planting. Little organic matter accumulation takes place thereafter, unless the plants are cut.

C. trichotoma is sometimes severely attacked by the fungus Parodiella spegazzinii, which covers the upper surface of the leaves with a black soot-like layer. The affected leaves curl upwards and whole plantations can be destroyed. C. trichotoma is occasionally ravaged by Helopeltis antonii and - less severely - by Deiopeia pulchella. It is resistant to Ragmus importunatas bugs, but may act as a host plant for the legume pod borer (Maruca testulalis) and the lima bean pod borer (Etiella zinckenella).

Genetic resources and breeding

Germplasm collections of Crotalaria spp. are maintained by the United States Department of Agriculture, including material of C. trichotoma. It is unlikely that any substantial breeding programmes exist.

Prospects

C. trichotoma is a very suitable green manure crop in plantation crops on poor, compacted soils and where other, more productive crops cannot be grown because of disease and pest problems. More research is urgently needed, especially on its economics and its incorporation in cropping systems with annual crops.

Literature

• Gillett, J.B., Polhill, R.M. & Verdcourt, B., 1971. Leguminosae (Part 4), Subfamily Papilionoideae (Part 2). In: Milne-Redhead, E. & Polhill, R.M. (Editors): Flora of tropical East Africa. Crown Agents for Oversea Governments and Administrations, London, United Kingdom. pp. 911-913.
• Backer, C.A. & van Slooten, D.F., 1924. Geïllustreerd handboek der Javaanse 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. p. 132, 132a.
• Listeria, M.S., 1976. Pengaruh tumpang sari Crotalaria usaramoensis dengan jagung sebagai bahan pupuk organik pada tanaman kentang dan pengaruhnya terhadap produksi jagung berikutnya [Evaluation of intercropping of C. usaramoensis and maize as a source of green manure for subsequent crops of potato and maize]. Bulletin Penelitian Hortikultura 4: 47-52.
• Listeria, M.S. & Hekstra, A., 1976. Pengaruh kapur, pupuk NPK dan beberapa jenis pupuk organik pada tanaman-tanaman kentang, kacang jogo dan kubis [The effects of liming, NPK fertilizing and some other organic matter on potato, bean and cabbage]. Bulletin Penelitian Hortikultura 4: 3-13.
• Polhill, R.M., 1990. Légumineuses [Leguminosae]. In: Bosser, J., Cadet, T., Guého, J. & Marais, W. (Editors): Flore des Mascareignes. Vol. 80. The Sugar Industry Research Institute, Mauritius, L'Institut Français de Recherche Scientifique pour le Développement en Coopération (ORSTOM), Paris, France & The Royal Botanic Gardens, Kew, United Kingdom. pp. 200-202.
• Vidal, M.R.R., Vidal, W.N. & Mussury, R.M.A., 1990. Germinação e desenvolvimento da plãntula de Crotalaria zanzibarica Benth. [Germination and development of plantlets of C. zanzibarica]. Revista Ceres 37 (211): 185-198.

Authors

L.P.A. Oyen