Crotalaria juncea


Scientific name

Crotalaria juncea L.

Synonyms

Crotalaria benghalensis Lam.
Crotalaria fenestrata Sims
Crotalaria ferestrata Sims
Crotalaria porrecta Wall.
Crotalaria sericea Willd.
Crotalaria tenuifolia Roxb.
Crotalaria viminea Wall.

Family/tribe

Family: Fabaceae (alt. Leguminosae), subfamily: Faboideae, tribe: Crotalarieae. Also placed in: Papilionaceae

Common names

Cambodia: kk'tung
China: shu ma, tai yang ma (Taiwan)
English: brown hemp, Indian-hemp, Madras-hemp, sann-hemp, sunn crotalaria, sunn-hemp
French: cascavelle, chanvre du Bengale, chanvre indien, crotolaire jonciforme, grand sonnette, grand tcha-tcha (Creole), sonnette, tcha-tcha (Creole)
German: bengalischer hanf, bombay hanf, sanhanf
India: saab, san, sunn, sannai, sanpat, sonai, tag, vakku, janumu, ghore sun, shon, shonpat
Indonesia: orok-orok lembut
Kenya: mito
Laos: thang, thwax chu
Nepal: san
Philippines: putok-putukan, karay-kagay
Portuguese: cnhamo-da-ndia, crotalaria
Russia: krotalyariya sitnikovaya
Spanish: camo san
Sri Lanka: hana
Tamil: sanal, sannappu
Thailand: po-thuang
Vietnamese: cy mu?ng

Morphological description

Erect, herbaceous, laxly branched annual shrub, (1 -) 2 - 3 (- 4) m tall, with a deep strong tap root, and well-developed lateral roots bearing numerous multi-branched and lobed nodules, up to 2.5 cm in length.  Stem cylindrical, ribbed, pubescent to about 2 cm diameter, branching from about 60 cm, minimised with dense plantings.  Leaves simple, sparsely appressed-pubescent above, more densely so below, stipules acicular, 2 - 3 mm long, caducous; petiole about 5 mm long with pulvinus, blades bright green in colour, linear elliptic to oblong, entire, acute, sometimes sub-obtuse, 4 - 12 (- 15) cm long, 0.5 - 3 cm broad; spirally arranged on the stemInflorescence a lax indeterminate, terminal raceme (10 -) 15 - 25 (- 30 cm) long comprising 10 - 20 flowers, with very small linear bracts.  Pedicels 3 - 5 mm long; corolla bright or deep yellow; standard erect, sub-orbicular to short oblong, 2 - 2.5 cm diameter, sometimes streaked reddish or purple on dorsal surface; wings slightly shorter than keel; keel abruptly curved, the beak narrow and twisted at apex, c. 10 mm long; stamens 10, almost free to base (5 with short filaments and long narrow anthers, and 5 with long filaments and small rounded anthers); calyx 5-lobed, sepals pointed, tomentose, 11 - 20 mm long, 3 lower sepals united at base separating in fruit.  Pods tomentose, inflated, cylindrical, 2.5 - 4 (- 6) cm long, 1 -2 cm diameter, grooved along the upper surface, with a short pointed beak, light brown when ripe, 6 - 12-seeded.  Seed heart-shaped, with narrow end strongly incurved, flattened, (3 -) 4 - 6 mm long, greyish olive, dark grey, dark brown to black, loosened in the pod at maturity; 17,000 to 35,000 per kg (depending on production conditions and genotype).

Distribution

Exact native range obscure, although considered native to:
South Asia: Bangladesh; Bhutan; India (Andhra Pradesh, Arunachal Pradesh, Assam, Bihar, Delhi, Goa, Gujarat, Haryana, Himachal Pradesh, Jammu and Kashmir, Karnataka, Kerala, Madhya Pradesh, Maharashtra, Manipur, Meghalaya, Mizoram, Nagaland, Orissa, Pondicherry, Punjab, Rajasthan, Sikkim, Tamil Nadu, Tripura, Uttar Pradesh, West Bengal, Yanan.)

Other:
Cultivated throughout the dry and wet tropics particularly in India, Bangladesh, and Brazil; also to a lesser extent in the subtropics and even cool temperate steppe.

Uses/applications

While finding some application as a forage, it is primarily grown for production of bast fibres used in the manufacture of twine and cord, high quality paper and pulp; also used as a green manure or cover crop and as a break crop to reduce weed and nematode populations.

Ecology

Soil requirements

Grows on most well-drained soils.  For fibre, it is best on fairly light textured soil (sandy loam or loam) of at least moderate fertility, but for other purposes, it will also grow well on clay soils and tolerates low fertility, providing soils are well-drained.  While it is adapted to pH from 5 to 8.4, it is best in the near neutral range (pH 6 - 7), that favours phosphate availability.  Although C. juncea is mostly listed as having a low tolerance to salt, tolerance of moderate salinity is also claimed.

Moisture

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C. juncea is drought tolerant, being adapted to hot, semi-arid and arid areas, with average annual rainfall as low as 200 mm.  Irrigation is necessary for maximum growth and nitrogen fixation (minimum of 25 mm of water/wk).  It is also more productive with relatively high humidity.

Temperature

C. juncea is grown in India from 17 - 30 N, in areas with 24-hour average annual temperature (AAT24) of 15 - 27.5 C, in Brazil, from the equatorial conditions of the Amazon belt to 22.5 S in the State of So Paulo (AAT24 18 - 27 C), and in Nepal to about 1300 m ASL (e.g. Kathmandu 27 42' N, 1,300 m ASL, AAT24 18.6 C).  Elsewhere, it is grown in areas with AAT24 as low as 8.4 C, providing there is a frost-free growing period of 2 - 3 months.  Although it can tolerate light frosts, with -2 C the minimum tolerated without injury, growth and nitrogen fixation are reduced under cool conditions.

Light

Any reduction in light results in a growth reduction.

Reproductive development

C. juncea is primarily a short day species in its flowering response, although day neutral types, SUEX 015 and T-6, have been identified. Vegetative growth is favoured by long days in the day neutral types, whereas SUEX 015 flowers in 30 - 35 days irrespective of sowing time.  Date of sowing therefore has direct bearing on the vegetative growth and development.  The crop sown immediately after the break of the monsoon gives significantly higher yields than those obtained from crops sown later.  The lowest flowers of the inflorescence generally open first and remain open for 2 days.  Details of anthesis and pollination can be found at Sun hemp in India.  Extensive cross-pollination occurs and self-pollination only takes place after the stigmatic surface is stimulated by the bee or mechanically.

Defoliation

Plants remain succulent for 6 to 8 weeks after sowing, at which time flowering begins and stems begin to lignify.  When grown for forage, C. juncea can be harvested 4 times, starting 6 - 8 weeks after sowing, and then every 4 weeks.  This is also the best time to incorporate it as a green manure.  More mature plants are set back by harvesting and may die or take some time for even partial recovery.

Fire

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No information

Agronomy

Establishment

Seed can be broadcast (35 - 50 kg/ha) or drilled in 20 - 30 cm rows (25 - 40 kg/ha), preferably placing seed at 1 - 2 cm depth into a clean, well-prepared seedbed.  Higher seeding rates should be used if the crop is to be incorporated within 30 - 45 days, or if severe weed competition is likely.  It appears to be fairly promiscuous in its rhizobial requirements, but inoculation of seed with cowpea strain Bradyrhizobium, will help to ensure effective nodulation.  Germination is epigeal and seed germinates in about 3 days.  Under favourable conditions, stands can attain a height of over 1 m in 60 days or 2 m in 90 days. (see "Seed production")

Fertiliser

Although it is more tolerant of low fertility than some other green manures such as Vigna unguiculata , it responds to applications of phosphorus in particular on poorer soils.  For maximum yields, a soil test should be taken and fertiliser and soil amendments added as required.

Compatibility (with other species)

C. juncea is most commonly grown in monoculture as a green manure/cover-crop.  However, it may be grown in companion sowings with a number of taller grain/forage crops, and trellised vines.

Companion species

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Grasses: Pennisetum glaucum, Sorghum bicolor, Zea mays.

Legumes: Normally not sown with other legumes.

Pests and diseases

Sunn hemp is attacked by many diseases and pests, and with its being so widely cultivated, these pests and diseases are often specific to particular regions.  Anthracnose or stem -break, caused by Colletotrichum curvatum, and wilt caused by Fusarium udum var. crotalariae are the main fungal diseases.  The former causes wilt and weakening of the stem, while the latter mostly affects young plants causing wilt and necrosis, and yellowing of the leaves in older plants leading to eventual death.  Other fungal diseases include rust (Uromyces decoratus), Sclerotinia rot, powdery mildew (Oiduim sp.), wilt (Ceratocystis fimbriata), and twig blight (Choanephora cucurbitarum).  Sunnhemp mosaic virus transmitted by silverleaf whitefly (Benisia tabaci: Hemiptera: Aleyrodidae), causes yellowing and crinkling of the leaves and weak stems that lodge easily, resulting in low fibre yields.
Main insect pests are the sunn hemp moth (Utetheisa pulchella: Lepidoptera: Arctiidae), larvae of which damage leaves and pods, and the stem borer (Enarmonia pseudonectis: Lepidoptera: Tortricidae).  Other damaging insects include the top-shoot borers (Laspeyresia pseudonectis and L. tricenta,: Lepidoptera: Eucosmidae), which bore into the apical tip of the plant, causing excessive branching and stopping growth, lima bean pod borer (Etiella zinckenella: Lepidoptera: Pyralidae) and the bella moth (Utetheisa bella) both of which attack pods, leaf-feeding caterpillars (Argina cribraria and A. syringa: Lepidoptera: Arctiidae), stem - or shoot-borers Cymotricha tetraschema (Lepidoptera: Gelechiidae) and Selinas monotropa, leaf eating beetle (Exora sp.: Coleoptera: Chrysomelidae), aphids (Aphis spp.: Hemiptera: Aphidae), the bean butterfly (Lampides boeticus: Lepidoptera: Lycaenidae), a sap sucker (Ragmus importumitas: Hemiptera: Miridae), flea beetle (Longitarsus belgaumensis: Coleoptera: Chrysomelidae); green vegetable bug (Nezara viridula: Hemiptera: Pentatomidae) and African sorghum head bug (Eurystylus oldi: Hemiptera: Miridae)
C. juncea is susceptible to parasitisation by the dicotyledonous species, Striga asiatica, S. hermonthica, and S. lutea.
Damage from insects and disease tends to be more severe if crops are planted in the same area for more than three consecutive years.  Resistance and field tolerance to some of the above pests and diseases has been identified, providing a basis for varietal selection.  Resistance of many varieties to root knot nematode (Meloidogyne spp.) makes this a useful break crop for more susceptible crops.

Ability to spread

No information.

Weed potential

USDA warns "This plant may become weedy or invasive in some regions or habitats and may displace desirable vegetation if not properly managed."  However, it does not feature prominently in weed lists and received a Weed Risk Assessment score of -3 by Pacific Island Ecosystems at Risk (PIER), which indicates "Low risk".

Feeding value

Nutritive value

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Nitrogen content is greatest at the onset of floral initiation to mid bloom, and declines as N reserves are allocated to seed development.  Crude protein values range from 12.5 to 15% in green material, with corresponding NDF values of 35.3 and 41%.  In other, possibly more mature samples, CP values of 10.0 - 13.7% coincided with NDF values of 62.5 - 55.5%.  Calcium levels range from 0.7 - 2.1%, and phosphorus from 0.2 - 0.5%.

Palatability/acceptability

When fresh, it is not readily eaten by ruminants, but is well accepted once dry.

Toxicity

As with many other members of the genus, C. juncea contains pyrrolizidine alkaloids, which are converted into potent toxins in the liver.  Highest alkaloid levels are found in the seeds.  Toxicity varies from toxic to non-toxic among genotypes.  Laboratory tests and feeding trials with the Hawaiian variety, 'Tropics Sun', suggest that both seeds and forage of are nontoxic.  Stress conditions may also affect the degree of toxicity.  To reduce chances of poisoning, it is best to limit C. juncea forage intake to no more than 45% in rations for sheep, 10% for cattle, and not fed at all to horses and pigs.

Production potential

Dry matter

Yield potential varies with soil fertility and growing conditions generally.   In monsoonal climates, the crops sown immediately after the break of the monsoon give significantly higher yields than those obtained from crops sown later.  Crops develop quickly, with reported yields as high as 2 t/ha of high quality DM in 6 - 8 weeks.  Total green matter yields range from 5 - 18 (- 27) t/ha.  Annual dry matter yields of 12.5 - 14 t/ha depending on level of fertiliser application, are also reported.  Yields can be reduced by about 25% by weed competition.

Animal production

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No information.

Genetics/breeding

2n = 16.  It is primarily an out-crossing species, but successful efforts in breeding for self-compatibility, making cultivar maintenance more reliable, have been reported.  Even though there is frequent reference to foliage being fed to livestock, there appears to have been no programme specifically designed to select forage cultivars of the species.

Seed production

Since it is a highly cross-pollinated species, it is important to have seed crops sufficiently isolated from other stands of C. juncea to avoid genetic contamination of cultivars.  Crops are best grown in areas where winter temperatures do not fall below 10 C.  Planting time is determined to enable the plants to dry naturally, so that flowering, seed set, and harvest occur during the dry season.  Row spacing of 90 to 105 cm, with about 10 seeds/m within the row, facilitates plant development, weeding, irrigation and harvesting.  The crop should be irrigated, if necessary, until about 75% of plants are flowering (about the end of the third month), and monitored for insect and disease build-up, spraying as needed.  Pods are harvested when they rattle.  For machine harvest, the concave clearance is initially set at 3 - 5 mm, and the cylinder speed at 1150 to 1200 RPM, and adjusted as needed according to crop conditions.  Seed yields vary considerably, depending on variety, time of planting, weed competition and incidence of pests and diseases.  Seed yields under optimum conditions range from 1.8 - 2.5 t/ha, but more commonly from 0.5 - 1 t/ha.  Seed should be dried to below 10% moisture and stored at low temperature and humidity.

Herbicide effects

Little information available.  Related species susceptible to 2,4-D.  Minimal phytotoxicity reported for several pre-emergence herbicides including clomazone at 1.38 kg a.i./ha.

Strengths

  • adapted to poor soils
  • very effective nitrogen fixation
  • drought tolerant
  • nematode resistant

Limitations

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  • intolerant of poor drainage
  • insect and disease susceptibility
  • frost-tender
  • toxicity of some varieties
  • forage quality declines rapidly on flowering

Other comments

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Selected references

Chee, Y.K. and Chen, C.P. (1992). Crotalaria juncea (L.)  In 't Mannetje, L. and Jones, R.M. (eds), Plant Resources of South-East Asia No 4 Forages.  pp 98 - 100 (Pudoc Scientific Publishers, Wageningen.)
Pandey, B. N. and Sinha, R. P. (1977) Light as a factor in growth and morphogenesis i. effect of artificial shading on Crotalaria juncea L. and C. sericea retz. New Phytologist 79, 431 - 439.
Rotar, P.P. and Joy, R.J. (1983). 'Tropic Sun' sunn hemp Crotalaria juncea L. Hawaii Institute of Tropical Agriculture and Human Resources, University of Hawaii at Manoa, Honolulu, Hawaii, United States. 7 pp. Research Extension Series 036.
Strickland, R.W., Lambourne, L.J. and Ratcliff, D (1986) The palatability, feeding value and apparent toxicity of 150 legume species fed to rats.  Genetic Resources Communication Number 10. CSIRO, Division of Tropical Crops and Pastures, St Lucia, Brisbane, Qld, Australia. ISBN 0643-03683 0.
Strickland, R.W., Lambourne, L.J. and Ratcliff, D (1987) A rat bioassay for screening tropical legume forages and seeds for palatability and toxicity. Australian Journal of Experimental Agriculture 27, 45 - 53.
Wang, K.-H., Sipes, B.S., and Schmitt, D.P. (2002) Crotalaria as a cover crop for nematode management: a review. Nematropica 32, 35 - 57.
White, G.A. and J.R. Haun. 1965. Growing Crotalaria juncea, a multi-purpose fiber legume, for paper pulp. Economic Botany 19, 175 - 183.
Yost, R., and Evans, D. (1988).  "Green manures and legume covers in the tropics."  Hawaii Agricultural Experiment Station.  HITAHR College of Tropical Agriculture and Human Resources.  Research Series 055.  pp 16 - 17.

Internet links

Cultivars

Cultivars

Country/date released

Details

Numerous   Various C. juncea is primarily grown as a fibre and green manure crop.  Each country has its own range of cultivars, selected on the basis of their suitability for the application in that country or region.  Cultivars vary in terms of yield, fibre quality, flowering response, disease and insect tolerance, soil adaptation, etc.

Promising accessions

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Promising accessions

Country

Details

No information - -