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Graminae
Common names
Var. major: alang-alang or lalang (Malaysia), kunai (New Guinea),
blady grass (Australia), cotton wool grass, spear grass (Nigeria). Var.
africana: silver spike (southern Africa), cogon grass (Philippines), cotranh
(Viet Nam), illuk (Sri Lanka), yakha (Laos), gi (Fiji), sword grass (Zaire).
Description
A perennial up to 120 cm high with narrow, rigid leaf-blades.
Lower leaf-sheaths bearded at the mouth, upper usually glabrous; blades
glabrous or hairy on the lower part, up to 100 cm long, often less, usually
3-10 mm wide, expanded; panicle 5-10 cm long; spikelets surrounded by hairs
1015 mm long. Imperata roots penetrated to 58 cm in alluvial soil at Varanasi,
India, with a production of 20 480 kg air-dried roots per hectare (Ramam,
1970). There are five varieties. 1. cylindrica var. africana has the culm
nodes usually glabrous and the spikelets 5 mm long, while in var. major
the culm nodes are bearded and the spikelets to 3.5 mm long (Napper, 1965).
Var. europaea occurs in Europe, var. Latifolia in Tibet and var. condensata
in Chile (Hubbard et al., 1944).
Distribution
India, Australia, eastern and southern Africa and other warm
temperate and tropical regions of the world.
Altitude range
Sea-level to 2 000 m in the Himalayas.
Rainfall requirements
It grows over a wide rainfall range of 250-6 250 mm, with maximum
performance over 1 500 mm.
Drought tolerance
It can survive quite long droughts because of its rhizomes.
Soil requirements
It generally occurs on light-textured acid soils with a clay
subsoil, but can tolerate a wide range of soils from strongly acidic to
slightly alkaline, with a pH of 4.0-7.5, but germination is promoted by
a pH of less than 5.0 (Sajise, 1973).
Ability to spread naturally
It spreads readily by rhizomes and seed. If the rhizomes are
cut by cultivation, propagation can take place from pieces with as few
as two nodes.
Seedling vigour
It establishes well in a burn.
Vigour of growth and growth
rhythm
More than 80 percent of shoots originate from the rhizomes
less than 15 cm below the soil surface (Ivens, 1970).
Response to defoliation
It cannot stand continuous heavy grazing and in Thailand it
is superseded by weeds if grazed very heavily. Repeated cutting and rolling
will weaken the stand and the rhizomes can be destroyed by systematic cultivation.
Grazing management
If the grass is not to be eradicated, it can be burnt periodically
and grazed rotationally when 15-25 cm high.
Dry-matter and green-matter
yields
In Indonesia it was found that the average number of shoots
of Imperata at the places studied was 4.5 million per hectare, producing
11 500 kg of leaves and 7 000 kg of rhizomes (Soerjani, 1970). Chadokar
(1977) followed the nutritive value of Imperata cylindrica at two-week
cutting intervals after burning at Erap, Papua New Guinea.
Suitability for hay and
silage
Most of the hay material is used for thatch and is not for
fodder. It can be used as low-quality roughage in conjunction with concentrates
(Soewardi et al., 1974).
Diseases
No major diseases affect it.
Optimum temperature for
growth
30°C, maximum 40°C.>
Minimum temperature for
growth
20°C.a
Ability to compete with
weeds
Imperata competes very successfully with weeds and suppresses
them, but it is an important weed in its own right.
Pests
In Indonesia, a gall fly (Urseoliella javanica) attacks the
apical meristem (Soerjani, 1970) but is itself heavily parasitized by a
Chalcid wasp which destroys some 50 percent of the larvae. It exerts some
biological control.
Palatability
It is eaten by livestock in the young stage, but avoided in
the mature state. Elephants eat it in the Queen Elizabeth National Park,
Uganda, during the dry season (Field, 1971). The extreme point and the
margins of the leaves are sharp, causing irritation in the mouth, so cattle
do not like it (Soerjani, 1970). The rhizomes are eaten by pigs.
Chemical analysis and
digestibility
Göhl (1975) lists analyses from Pakistan, India and Malaysia.
Natural habitat
Subhumid and humid grassland and open woodland.
Tolerance to flooding
It cannot stand continuous flooding and flooding is one method
of control.
Fertilizer requirements
Chadokar (1977) found that yields of Imperata responded markedly
to increased nitrogen rates, but nitrogen had less effect on improving
the protein content.
Compatibility with other
grasses and legumes
It usually forms a monospecific sward by repeated burning.
Bor (1960) stated that in the Philippines the leguminous shrub Leucaena
leucocephala can grow with it and upgrade its forage value.
Genetics and reproduction
2n=20 (Fedorov, 1974).
Economics
It covers more than 16 million hectares of waste land in Indonesia,
with an annual increase of more than 150 000 hectares. Another 23 million
hectares are still used for shifting cultivation, which serves as a source
of area increase, and shifting cultivation increases by 100 000 hectares
annually. It is a noxious weed in rice, cotton, coffee, cinchona, tea,
oil-palm, coconut, rubber and teak plantations. It is used for soil erosion
control, mulch in coffee plantations, fodder, thatching, paper-making,
packaging, fuel, ornamental purposes and for the sacrificial thread of
the Hindu and as a bouquet material in the marriage ceremony in Java (Soerjani,
1970). The rhizomes and root extracts are used medicinally. In Lesotho
rhizomes are eaten raw by herders and are used as a remedy for chest colds
in children.
Animal production
The young shoots make good pasture (Henty, 1969). In Papua
New Guinea, Holmes, Lemerle and Schottler (1976) recorded liveweight gains
of 0.22, 0.25, 0.21 and 0.20 kg per day at stocking rates of 0.78, 0.94,
1.25 and 1.64 beasts per hectare for heifers grazing Imperata pasture,
compared with the highest weight gain of 0.45 kg per day for heifers grazing
a Hamil grass/legume pasture at a stocking rate of 1.69 and 2.17 beasts
per hectare. In the Philippines, Magadan, Javier and Madamba (1974) recorded
live-weight gains of cattle grazing Imperata at a stocking rate of one
beast per hectare as 0.27 kg per day or 100 kg per year compared with the
gain on Para/ centro pastures, which was more than three times this figure.
In Florida, 52.4 kg beef per hectare were produced from grass alone. Imperata
mixed with Panicum repens, unmanured, yielded 61.9 kg/ha. In the Thai highlands
(Falvey & Andrews, 1979) the local cattle gain was about 16 kg live-weight
gain per animal per year.
Further reading
Falvey, 1980; Falvey, Hengmichai & Hoare, 1979; Soerjani,
1970.
Dormancy
There is no dormancy. Germination of the seed in the dark increased
from 9 percent at 20°C, to 55 percent at 30°C, declined somewhat
at 35°C, and was about 70 percent in the light with alternate 12-hour
periods at 20 and 30°C. 0.2 percent KNO3 solution increased germination
in the dark, but not in the light. Germination declined gradually after
13 months' storage (Dickens & Moore, 1974).€#S
Value for erosion control
It is effective in controlling erosion, but there are more
useful fodder grasses which can also stabilize the soil. In eastern Nepal,
of four grasses tested for soil binding Imperata cylindrica, Brachiaria
mutica, Cynodon plectostachyus and Cymbopogon spp. Imperata produced
the most "roots" (rhizomes and roots): 3 620 kg DM/ha in the top 7.5 cm
of soil in its second year of growth and 4 574 kg/ha in its third year
(Khybri & Mishra, 1967). It is used for stabilizing mine dumps in Zimbabwe
(Hill, 1972).
Tolerance to fire
Frequent fires encourage the uniformity of an Imperata sward,
and generally it occurs as a fire disclimax. The leaves burn readily, and
regrowth from rhizomes is rapid (Chadokar, 1977).
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