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Crotalaria juncea L.

Fabaceae
Sunnhemp, Indian hemp, Madras hemp, Brown hemp, Sannhemp

Source: James A. Duke. 1983. Handbook of Energy Crops. unpublished.

  1. Uses
  2. Folk Medicine
  3. Chemistry
  4. Description
  5. Germplasm
  6. Distribution
  7. Ecology
  8. Cultivation
  9. Harvesting
  10. Yields and Economics
  11. Energy
  12. Biotic Factors
  13. References

Uses

Sunnhemp is cultivated for the strong bast fiber extracted from the bark, which is more durable than jute. Fiber is used in twine, rug yarn, cigarette and tissue papers, fish-nets, sacking, canvas and cordage. Sunn fiber is stronger when wet, and is fairly resistant to mildew, moisture and microorganisms in salt water. It is one of the oldest known fibers in the Indo-Pakistan subcontinent, as mentioned in ancient Sanskrit literature. It is widely grown throughout the tropics as green manure, the dried stalks and hay being used as forage for livestock. Although reported to be poisonous to livestock, seeds are fed to horses in the Soviet Union and to pigs in Rhodesia.

Folk Medicine

The seeds are sometimes used medicinally, said to purify the blood. Seeds are also used in impetigo and psoriasis, and as an emmenagogue.

Chemistry

Raw sunnhemp contains 0.61% ash, 9.6% hygroscopic water, 2.8% aqueous extract, 0.55% fat and wax, 80.0% cellulose, and 6.4% pectin bodies, (CSIR, 1950). Dried as cattle feed, the stalks contain 14.4% moisture, 1.1% ether extract, 11.3% albuminoids, 35.8% carbohydrate, 27.4% woody fiber, and 6.4% soluble mineral matter. Seeds contain 8.6% moisture, 34.6% crude protein, 4.3% fat, 41.1% starch, 8.1% fiber, and 3.3 ash. (CSIR, 1950). Seeds are reported to contain trypsin inhibitors, and are said to be poisonous to cattle. Seeds contain 12.6% oil, with 46.8% linoleic acid, 4.6% linolenic acid, and 28.3% oleic acid, with, by difference 20.3% saturated acids (Zafar et al, 1975).

Description

Tall herbaceous shrubby annual, 1-3 m tall, vegetative parts covered with short downy hairs; taproot long, strong, with many well-developed lateral roots, and numerous much-branched, lobed nodules up to 2.5 cm in diam. stems to 2 cm in diam.; leaves simple with minute pointed stipules; petiole short, about 5 mm long with pulvinus, blades linear elliptic to oblong, entire, 4-12 cm long, 0.5-3 cm broad, bright green; inflorescence a terminal open raceme to 25 cm long with very small linear bracts; flowers showy, small with 5 hairy sepals, shortly united at base, the lobes pointed, with 3 lower sepals united at tips, separating in fruit; petals deep yellow, the standard erect, about 2.5 cm in diam., rounded, sometimes streaked purple on dorsal surface, the wings shorter and keel twisted; stamens 10, almost free to base, 5 with short filaments and long narrow anthers and 5 with long filaments and small rounded anthers; fruit an inflated pod about 3 cm long, 1 cm wide, grooved along the upper surface, with a short pointed beak, light brown when ripe, several seeded, softly-hairy; seeds numerous, small, flattened, dark-gray to black, loose in the pod at maturity, 33,000 seeds per kg. Fl. July-August in Rhodesia.

Germplasm

Of several well-recognized types, best known in Pakistan are 'Madaripur' and 'Serajgnaj', the first one considered best, having creamy-white fibers of good strength, relatively free from dirt. There are cvs for different rainy seasons: 'Bhadai san', May, June-Oct., Nov.; 'Rabi san', Oct., Nov.-Feb. 'Somerset' is a good cv in Rhodesia. In India kharif and rabi sunnhemps are known. 'T6' is day neutral. 'Cawnpore 12' proved cv of 'Kharif sunn' of India, is superior in yield to all other types, although it is a longer growing cv requiring 2-2 1/2 months longer than 'Beldanga Early'. It is resistant to stem-break disease. 'Ullapora', a rabi variety, is superior in yield and quality. 'Tropic Sun' is resistant to root-knot nematodes. Its seeds and forage are nontoxic in laboratory tests and feeding trials (Rotar and Joy, 1983). Assigned to the Hindustani Center of Diversity, sunnhemp or cvs thereof is reported to exhibit tolerance to disease, drought, insects, laterite, nematodes, poor soil, slope, virus, and weeds. (2n = 16).

Distribution

The origin is uncertain, but is believed to be native to India and Pakistan. Now cultivated throughout India (from the foothills of the Himalayas to Ceylon), Pakistan, in Uganda and Rhodesia, and in the western Hemisphere (e.g. Brazil) where it was introduced early in the 19th century.

Ecology

Sunnhemp is the fastest growing species of the genus and is very effective in smothering weeds. Almost any well-drained soil is suitable for the kharif crop. Sunnhemp grown during the rainy season is utilized mainly as a green manure, the fiber not considered of good quality. For fiber sunnhemp is grown on fairly light well-drained soils that retain sufficient moisture during the growing season. Sunnhemp is a short-day crop, but vegetative growth is favored by long days, although seed set may be poor. Although tolerant of drought, sunnhemp has low tolerance to salt and frost. Ranging from Cool Temperate Steppe to Tropical Very Dry through Tropical Wet Forest Life Zones, sunnhemp is reported to tolerate annual precipitation of 4.9 to 42.9 dm (mean of 29 cases = 14.9 dm), annual mean temperature of 8.4 to 27.5°C (mean of 29 cases = 22.5°C), and pH of 5.0 to 8.4 (mean of 24 cases = 6.2).

Cultivation

After plowing, seed is broadcast by hand or a device consisting of a canvas bag containing the seed with a blower attached. Then the land is cross-plowed. Seed is sown at different rates at different times depending on the use of the crop. In India seed is broadcast for fiber at a rate of 96 kg/ha under dry growing conditions, and less on irrigated fields. In Pakistan seed is sown at rate of 120 to 240 kg/ha. The heavy seed rate insures upright erect stems which help to smother weeds, produces a finer fiber and increases the yield. Height of stalks in crops varied from 1.15 m to 1.75 m (to 2 m), with an average thickness of 1.2 cm about the middle of the stalk. Seed is sown in Africa in late Nov. and Dec., even as late as Jan., except for weeding, which is usually not necessary if the land has been well prepared; no cultivation is required. Sunnhemp is a dryland crop. Where irrigated, furrows are opened in fields separating them into small plots. If there is no rain after sowing, field is irrigated along these furrows. Crop is irrigated once in 10-15 days, lightly compared to other crops, like tobacco and chilies. Too much moisture is harmful during the first 2 weeks after germination. Seeds germinate rapidly. In about 3 days seedlings appear above ground and soon form a thick cover. No manure is applied. Sunnhemp is often grown as a green manure, in rotation with tobacco, vegetables, dry grains, rice, corn, cotton, also sugar cane, pineapples, coffee, and orchard crops.

Harvesting

In some areas plants are harvested at the flowering stage, (100-108 days). In Rhodesia the crop is cut when stems have turned yellow along the major portion of their length. If grown for seed, plants are harvested after seed are well set, and before pods are dry, so that no seed is lost during cutting and bundling prior to threshing. In Pakistan crop is harvested when pods are ripe. Harvesting at flower stage gives a finer fiber, but profit obtained from the seed crop is thereby lost. There are no significant differences in strength and quality of fiber obtained from plants retted at flowering time and those retted when seeds are fully mature. With kharif crop it is difficult to secure both fibers and seeds from the same crop, because by the time pod ripens, cold weather has set in, and hard stems do not ret well. Plants are cut with knives or pulled and allowed to remain in the field for 1 or 2 days until dried leaves fall off easily. Stalks are then tied into bundles and retted for 4-6 days. However, in Rhodesia, 10-14 days are required during July, 8-9 days in August and 5-8 in September-October. The number of days required for retting depends on water temperature, locality, time of year, weather conditions, depth and source of water, thickness of stalks, and quantity of straw in relation to volume of water. Cement tanks are preferred for retting, but earth pits, dams, weirs, streams, and backwater pools of rivers are also used. Shallow water from 1-1.3 m deep is satisfactory. If more than one ret is to be carried out in a pool, sufficient flow of water must be maintained to prevent fouling the water, which discolors the fiber. Four or five men are required to remove and stack one ton of straw per day. Bundles are stood on end (15-20 placed with butts on ground at a sufficient angle to permit air circulation in all directions). In this way the straw dries in 1-2 weeks. By standing each bundle up and fanning out the butts, drying time is reduced to 4 days. By leaning bundles on each side of a rack, drying time is reduced to 3-4 days. Various machines are used to decorticate the straw. A 6 h.p. engine is minimal for economical and speedy decortication. After the fiber is stripped from the stalks by hand, it is washed and hung over bamboo poles to dry in the sun. Cut straw with a yellowish tinge requires 10 days to 3 weeks to bleach out sufficiently so as to have a fiber of a satisfactory color. Stems cut while green will bleach out when exposed directly to the sun but have to be turned at least twice. For seeds, a crop is allowed to stand until pods are fully ripe. Stems are cut close to the ground and left in the field to wither for a few days, reducing the retting period for fiber extraction. In humid districts in Ceylon this cannot be done since the fiber deteriorates. After all leaves are removed, stems are bundled and stored for additional drying. They are then threshed by beating small bundles held by hand against a plank, placed in a sloping position over a threshing mat, and pods separated. Dried stems are then ready for retting.

Yields and Economics

Handweeded South Carolina material given ca 20:25:50 NPK/ha yielded ca 12.5 MT DM/ha, with ca 40:55:100 NPK/ha yielded ca 13 MT DM/ha, with ca 60:80:150 NPK/ha yielded ca 14 MT DM/ha. Corresponding unweeded yields were ca 9, 10, and 11 MT DM/ha (White and Haun, 1965). Seed yields run from 500 to 1000 kg/ha (to 2470 kg/ha according to Rotar and Joy, 1983). Average fiber yields are 560-900 kg/ha. In Rhodesia 330 kg line fiber/ha; in Pakistan 500-600 kg/ha. Strength of cordage fiber of sunnhemp is 185 kg, as compared to 157 kg for cotton rope, 132 kg for hemp and 102 kg for coir. Fiber elements are easily separated with sodium hydroxide solution or chromic acid. Extracted fiber is about 0.5-1.0 cm long, with an average diameter of 0.03 mm, among the broadest of bast fibers. World production of sunnhemp is 130,000 MT, principally produced by India, Brazil, West Pakistan. Sunnhemp exported from Calcutta is classed as Benares, Green or Raigarh hemp or Bengal hemp. There is a keen demand for Jaffna sunnhemp stems because local fishermen consider it superior to Indian sunnhemp fiber which is only purchased when Jaffna fiber is short. A hectare of crop was valued at 120-180 rupees depending on the quality. Fiber was valued at ca 60 rupees/kg, but was rarely sold because of its value to the fisherman. India grows about 360,000 hectares of sunnhemp annually, producing between 80,000 and 100,000 MT fibers, with about 20-30% being exported to the United Kingdom, United States, and Belgium.

Energy

DM yields as high as 7 MT/ha are reported in as little as 60 days along with N-fixation of 150 to 165 kg/ha (Rotar and Joy, 1983). Duke's phytomass files suggest yeilds of 4-5 MT/ha, but as indicated above, yields of 9-14 are possible with weeding and fertilization. If the crop is grown strictly for fiber, all the residues may be used for energy and mulch. Or one can extract 160 to 336 kg protein/ha (cf. 186 for Sesbania sesban, Jadhave et al, 1979).

Biotic Factors

Being a leguminous plant, sunnhemp is cross-fertilized by bees. It is attacked by many fungi: Alternaria crotalaticola, Aspergilla versicolor, Ceratocystis fimbriata, Ceratostomella fimbriata, Cercospora canescens, C. crotalariae, C. demetrioniana, Chaetomium globosum, Cladosporium herbarum, Colletotricum crotalariae-junceae, C. curvatum, Corticium solani, Corynespora cassiicola, Curvularia penniseti, Dactuliophora tarrii, Fusarium acuminatum, F. equiseti, F. lateritium, F. moniliforme, F. oxysporum, F. scirpi, F. undum, F. vasinfectum, Gibberella fujikuroi, Leveillula taurica, Macrophomina phaseoli, Microsphaeria diffuse, Mycosphaerelia pinodes, Myrothecium roridum, Nematospora coryli, Penicillium wottmanni, Periconia epiphylla, Phyllosticta crotalariae, Sclerotium rolfsii, Sphaerella crotalariae, Synchytrium phaseoli-radiati, Thielaviopsis basicola, Uromyces decoratus. The following bacteria also infect sunnhemp: Bacillus megatharium, Pseudomonas cyamopsicola, Ps. syringae, Ps. viridiflora, Xanthomonas patelii, and X. vignicola. The following viruses have been isolated: alfalfa mosaic, alsike clover mosaic, bean chlorotic ringspot, bean mosaic, bean necrosis, Brazilian tobacco streak, chlorotic mottle, mosaic (Marmor vignae var. catjang), mosaic, and witches broom. Striga asiatica, S. hermonthica, and S. lutea are parasitic on sunnhemp. Black beetles are serious pest in Rhodesia. The two most important and serious insect pests are the sunnhemp moth (Utethesia pulchella) and the stem borer (Enarmonia pseudonectis). Pod borers lower seed production. Among the nematodes are Anguina sp., Aphelenchoides sp., Ditylenchus sp. Helicotylenchus canescens, H. cavenessi, H. dihystera, Heterodera glycines, Meloidogyne hapla, M. incognita acrita, M. thamesi, Peltamigratus negeriensis, Pratylenchus brachyurus, P. coffeae, P. vulnus, Rotylenchulus reniformis, Rotylenchus coheni, Scutellonema clathricaudatum, Trichodorus sp., Tylenchus sp., and Xiphinema longicaudatum.

References

Complete list of references for Duke, Handbook of Energy Crops
last update July 8, 1996