Canavalia ensiformis (PROSEA)
Canavalia ensiformis (L.) DC.
- Protologue: Prodr. 2: 404 (1825).
- Family: Leguminosae
- Chromosome number: 2n= 22
Dolichos ensiformis L. (1753), Canavalia gladiata (Jacq.) DC. var. ensiformis (L.) Benth. (1859-1862).
- Jack bean, horse bean (En). Fève Jacques (Fr)
- Indonesia: kacang parang (Malay), kara bedog, kacang mekah (Sundanese)
- Malaysia: kacang parang putih
- Philippines: habas (Tagalog), lagaylay (Visaya), badang-badang (Ilokano)
- Cambodia: tiehs
- Laos: thwâx fak ph'aaz
- Thailand: thua khaek
- Vietnam: (cây) dâu ra, dâu tây, dâu ngua.
Origin and geographic distribution
Jack bean originates from South and Central America. It is widely cultivated in the southern United States since prehistoric times, and has been discovered in archaeological sites in Mexico dated 3000 BC. Now it is commonly cultivated throughout the tropics.
Jack bean is a forage for ruminants and is grown extensively as a cover crop or green manure crop in rotation with a wide range of crops. As a forage it is usually sun-dried before feeding to cattle, but may also be made into silage. Heat-treated ripe seed, when ground, is used as a concentrate in cattle and poultry rations. Half-ripe seeds are mixed with sorghum for feeding cattle in Hawaii. Young seeds and pods may be used in human nutrition as a vegetable but only when cooked. Soaked and roasted ripe seeds are eaten as a delicacy in Indonesia, but outside Japan and tropical Asia, the species is now little grown as a food crop for humans. The seed is sometimes roasted and ground to make a coffee substitute. In Indonesia flowers and young leaves are steamed and used as a flavouring.
Urease extracted from the seed is used in analytical laboratories. In Indonesia and China, heat-treated seeds and pods are used as medicine, and it has been suggested that some of the chemical constituents of jack bean might be used for medicinal purposes or for control of pests.
The forage is not especially palatable, but cattle can acquire a taste for it; dry forage is more palatable than fresh. Nitrogen concentrations of the forage and seed are 2.2-2.6% and 3.8-5.7% respectively. Non-ruminants fed on the seed show reduced weight gains, due mainly to the toxic amino-acid canavanine, which is an antimetabolite of arginine. Lectins (concanavalin A and B) are present in the seed and can inhibit the absorption of nutrients. Heat treatment of the seed overcomes the toxic effects. Seed weight ranges from 0.85-1.65 g/seed.
Annual or short-lived perennial climber with a deep root system, bushy, twining or prostrate, up to 2-3 m long. Stems become somewhat woody with age; branching is at lower nodes and some secondary branching also occurs. Leaves alternate, 3-foliolate; petiole 11-17 cm long, rachis 3-4.5 cm; leaflets ovate-elliptic, 5-20 cm × 3-12 cm, acute or rounded and mucronate at top, sparsely covered with short hairs on both surfaces, venation raised and reticulate. Flowers mauve to purple, or sometimes white, borne on an axillary raceme with swollen nodes each bearing 1-3 flowers on pedicels 2-5 mm long; peduncle 10-35 cm, raceme up to 20 cm long; calyx campanulate, 5-lobed, sparsely pubescent; corolla with rounded standard, 2.7 cm long, rose to purplish. Pod oblongoid, laterally compressed, 15-35 cm × 3-3.5 cm, containing 8-20 seeds, each valve with a sutural rib and an additional rib just below it. Seed oblongoid, laterally compressed, ca. 21 mm × 15 mm × 10 mm, ivory or white, the hilum brown, 6-9 mm long.
Growth and development
Germination is epigeal; the juvenile leaves are fully expanded about a week after sowing. Hard-seededness has not been recorded. Early growth is slow, but after establishment the species is capable of rapid growth. Jack bean flowers 50-110 days after sowing, depending on the accession and on climate and soil conditions. The time from sowing to seed harvest is normally about 170 days. In temperate regions it flowers in summer or autumn; in the tropics it flowers throughout the year. In temperate areas beans remain unaffected when light frost kills the foliage.
Other botanical information
In the literature on Canavalia Adans., confusion exists on the identity of 3 closely related species: C. ensiformis (jack bean), C. gladiata (Jacq.) DC. (sword bean) and C. virosa (Roxb.) Wight & Arnott. C. ensiformis and C. gladiata are cultivated taxa, possibly derived from the wild (occasionally cutivated) C. virosa . These 3 taxa are considered as one species by some, and by others they are kept separate. A thorough taxonomic revision is needed to bring clarification. Most recent floras separate the 3 taxa as follows:
- C. ensiformis : standard ca. 2.5 cm long, rose to purple; pod up to 35 cm × 3.5 cm; seed ivory or white, hilum less than half as long as the seed.
- C. gladiata : standard ca. 3.5 cm long, white; pod up to 40 cm × 5 cm; seed red or red-brown, rarely white, hilum more than half as long as the seed.
- C. virosa : standard ca. 3 cm long, whitish veined mauve; pod up to 17 cm × 3 cm; seed brown or red-brown, marbled with black, hilum ca. half the length of the seed.
There are several cultivars and accessions of jack bean which differ in their growth habit. They are being tested and produced in Venezuela (Universidad de Venezuela, Facultad de Agronomía, Maracay). The bushy types are early-flowering, better adapted to low-rainfall areas and have low capacity for forage production. The viny or twining types are late-flowering but are better adapted to more humid areas and produce greater amounts of forage.
Jack bean is well adapted to the humid tropics, yet is hardy and can withstand periods of drought. Consequently, it grows in regions with annual rainfall ranging from 700-4000 mm. Although jack bean is a lowland plant, it is also grown at altitudes up to 1800 m. It grows best in full sunlight but has moderate shade tolerance. It is tolerant of a wide range of soil conditions including acid soils and highly-leached infertile tropical soils. It is less affected by waterlogging or salinity than other pulses.
Propagation and planting
Jack bean is propagated by seed in a range of densities from 30 cm × 30 cm to 100 cm × 150 cm at shallow depth. For green manure crops, it is sown at a rate of about 50 kg/ha in rows 0.6-1 m apart. With accurate placement, sowing rates of 10 kg/ha will suffice. Sowing at the start of the wet season is preferred in regions with about 1000 mm annual rainfall, but in more humid environments sowing should be delayed until the end of the wet season.
As a pulse, jack bean may be grown with other crops such as maize or cassava. Although the grain yield of jack bean is then likely to be reduced, sometimes by as much as 50%, the total productivity of the system is improved.
Inoculation is normally unnecessary as jack bean nodulates promiscuously and effectively with rhizobia present in most soils. Twining forms grown for grain are sometimes grown on trellises since the improvement in light utilization improves pod yield and the pods are kept off the ground.
Diseases and pests
Jack bean is little affected by diseases and pests. A fungal root disease and a stem-borer sometimes cause serious losses. Platiprosopus acutangulus , a leaf-eating chrysomelid beetle, may cause serious problems during the early growth of the crop. Stored seed is quite resistant to pests and diseases, but can become infested with Tricorinus tabaci .
Forage and seeds are mostly harvested by hand. Although flowering is fairly well synchronized, some green pods may still be present at harvest time, especially if water is still available.
Forage DM yields of up to 23 t/ha have been obtained in Hawaii and green fodder yields may exceed 50 t/ha. Grain yields average 800-1000 kg/ha (range: 400-1500 kg/ha, depending on rainfall distribution) but in experimental plots yields as high as 6000 kg/ha have been recorded in highly intensive agriculture.
Fresh forage is not palatable to ruminants and is eaten only in small amounts, although cattle gradually become more accustomed to it. Consequently, it is usually fed after drying as this increases intake. Ruminants can consume small quantities of untreated grain or meal without ill effects, but larger quantities can be toxic. Affected animals have a clear nasal discharge, become lame and cannot rise. Mucous membranes become muddy in appearance and clear urine is passed more frequently than usual. Heat-treatment overcomes this toxicity. Meal prepared from jack bean seed is more palatable to cattle if molasses is added to it. For non-ruminants, extensive boiling with one or two changes of water and peeling off the seed-coat is required before the mature seeds are edible. The beans may also be processed to produce a protein concentrate for use in formulated foods.
There are very limited genetic resources available of this species. Germplasm collections are available at the Faculty de Agronomía of the Universidad de Venezuela (Maracay, Venezuela) and the USDA (Georgia, United States).
Although largely self-pollinating, some 20% of flowers may be cross-pollinated by insects. Some selection for lines with low concentrations of canavanine has been carried out in Venezuela. Also, some cultivars have been selected with climbing or dwarf attributes.
As a forage crop, prospects for jack bean are limited since it is of only mediocre acceptability to ruminants, and has toxic properties if eaten when fresh. Furthermore, other annual leguminous forages are equally or more productive. As a leguminous crop with the residue providing useful forage, the comparative freedom of jack bean from disease and pest problems and its high yield in low input systems justifies the development of jack bean as a sole crop or in intercropping systems as a vegetable or a pulse crop.
- Allen, O.N. & Allen, E.K., 1981. The Leguminosae: a source book of characteristics, uses, and nodulation. Macmillan Publishers Ltd., London, United Kingdom, and The University of Wisconsin Press, Madison, Wisconsin, United States. p. 132.
- Bogdan A.V., 1977. Tropical pasture and fodder plants. Longman, London. p. 330.
- National Academy of Sciences, 1979. Tropical legumes: resources for the future. Washington, D.C. pp. 11, 54-59, 305.
- Perry, L.M., 1980. Medicinal plants of east and southeast Asia: attributed properties and uses. MIT Press, Cambridge, Massachusetts, United States. p. 209.
- Sauer, J., 1964. Revision of Canavalia. Brittonia 16: 142-144.
- Skerman, P.J., Cameron, D.G. & Riveros, F., 1988. Tropical forage legumes. FAO, Rome. pp. 229-230.
Y.K. Chee, J.B. Hacker, L. Ramirez & C.P. Chen