Crotalaria juncea L.
Sunnhemp, Indian hemp, Madras hemp, Brown hemp, Sannhemp
Source: James A. Duke. 1983. Handbook of Energy Crops. unpublished.
- Folk Medicine
- Yields and Economics
- Biotic Factors
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.
The seeds are sometimes used medicinally, said to purify the blood. Seeds are
also used in impetigo and psoriasis, and as an emmenagogue.
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).
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.
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).
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.
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).
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.
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.
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.
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,
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
Complete list of references for Duke, Handbook of Energy Crops
C.S.I.R. (Council of Scientific and Industrial Research). 1948-1976. The wealth
of India. 11 vols. New Delhi.
Jadhav, B., Tekale, N.S., and Joshi, R.N. 1979. Green-manure crops as a source
of leaf protein. Indian J. Agr. Sci. 49(5):371-373.
Rotar, P.P. and Joy, R.J. 1983. 'Tropic Sun' sunn hemp Crotalaria juncea
L. Univ. Hawaii Res. Ext. Ser. 0271-9916.
White and Haun, 1965
Zafar et al, 1975
last update July 8, 1996