Pennisetum polystachion (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Pennisetum polystachion (L.) Schultes

Protologue: Syst. Veg. Mant. 2: 146 (1824).

Family: Gramineae

Chromosome number: 2n= 32, 36, 45, 53, 54, 56, 78

Synonyms

Panicum polystachion L. (1759), Pennisetum setosum (Swartz) L. Rich. (1805), P. atrichum Stapf & Hubbard (1933), P. subangustum (Schum.) Stapf & Hubbard (1933).

Vernacular names

• Feather pennisetum (En)
• Malaysia: rumput ekor kucing, rumput berus kucing
• Philippines: ikug-kuting (Tagalog)
• Laos: hnhaaz khachoon
• Thailand: ya-khachonchop
• Vietnam: co' duôi voi nho'.

Origin and geographic distribution

P. polystachion is a native of tropical Africa and India but is widely introduced and distributed in Indonesia, Malaysia, Thailand, Fiji, Australia and generally throughout the tropics, but rarely beyond 23°N and 23°S.

Uses

P. polystachion is grazed and also cut for use as a fresh fodder or as hay. It is useful for controlling soil erosion, especially on sloping land. It is considered a weed in Thailand, Fiji and parts of Malaysia. The fully mature culms make good paper pulp.

Properties

Nitrogen concentrations in P. polystachion, before or at early flowering, are 1.8-2.8%, declining to 0.8% in older material. Similarly, P concentrations fall from 0.5-0.2%. Experiments in Thailand showed a DM digestibility of 60-70% and a DM intake by sheep of 363-536 g/head per day. After flowering, nutritive value and acceptability to animals decrease rapidly.

Botany

An annual or perennial tufted or spreading grass, 0.5-3 m tall with culms erect or geniculate, simple or branched. Leaf-blade linear, 10-50 cm × 5-18 mm, drooping, glabrous to soft hairy above. Inflorescence a cylindrical panicle, 5-25 cm × 13-26 mm, purple or brownish; spikelets sessile, 3-5 mm long, each enclosed by up to 30 cm long involucral bristles, two-flowered, only the upper floret fertile; bristles scabrous to densely ciliate, 20-50 per spikelet.

In northern latitudes (Thailand) it flowers in October and in southern latitudes (Fiji) in April. Seedlings grow vigorously early in the rainy season. There are conflicting reports about seed dormancy. Some say that seeds may have a dormancy period of 3-6 months and others indicate there is no dormancy. One report mentions that the germination percentage of P. polystachion seed was 6-8% after one year of storage, improving to 14-22% after two years. It is a prolific seeder.

P. polystachion is a polymorphic species, very variable in colour, stiffness and length of the bristles. In fact it is a complex species, formerly subdivided into the species mentioned under synonyms, which are now joined by a continuous pattern of variation. Sometimes the complex is subdivided into 3 subspecies (without clearly separating characteristics):

• ssp. polystachion : annual plant; involucral bristles 6-45, ciliate; 2 n = 32, 36, 45, 54.

• ssp. setosum (Swartz) Brunken: perennial plant; involucral bristles up to 50, densely to sparsely ciliate; 2 n = 53, 54, 56, 78.

• ssp. atrichum (Stapf & Hubbard) Brunken: perennial plant; involucral bristles up to 30, scabrous; 2 n = 36.

P. polystachion resembles P. pedicellatum Trin. and P. purpureum Schumach., but it can be distinguished by the lower lemmas which are often three-lobed, the upper florets which disjoint readily and rachises with decurrent wings on the ridge below the pedicels.

Ecology

P. polystachion is a short-day plant and mainly adapted to the lowland tropics, although it can be found at altitudes up to 2400 m. It grows well in high rainfall areas, but can also tolerate short dry periods. Its optimal temperature for growth is 32-35 °C with a minimum of 12 °C. It is adapted to a wide range of soil types, from light sandy soils to waterlogged clay soils, but it will not stand prolonged flooding. It often occurs on old farmland and other disturbed places. P. polystachion tolerates acid (pH(H₂O) 4.5) as well as alkaline soils. It is tolerant of shade and poor soil fertility, and is favoured by regular burning.

Agronomy

P. polystachion is best established by broadcasting seed on cultivated land, sowing at 3.5-4.5 kg/ha. It is usually not fertilized, but either chemical fertilizer or farmyard manure is sometimes applied in Fiji and India. There are no reports of any major diseases or serious pests. When used as forage, P. polystachion should be grazed or cut before flowering. When used as cut-and-carry forage, it can be cut 2-3 times a year. Cut forage can be fed fresh or conserved as hay, although the succulent stems are slow to dry. If it is prevented from flowering, P. polystachion will stay green well into the dry season. When subjected to sustained heavy grazing it will not persist and will be replaced by prostrate species. Legumes can be grown with P. polystachion , although fertilization with P may be required. When grown with a suitable legume in Fiji, P. polystachion was eaten more readily by cattle. Shade-tolerant legumes such as Desmodium heterophyllum (Willd.) DC., Desmodium heterocarpon (L.) DC. ssp. ovalifolium (Prain) Ohashi, and Centrosema pubescens Benth. can be grown with P. polystachion . Also Macroptilium atropurpureum (DC.) Urban and Stylosanthes guianensis (Aublet) Swartz have been successfully introduced into P. polystachion pastures after burning and with the use of P fertilizer. For pulp making, it should be cut after the seeds are fully ripe since pulp quality is best at this stage.

In Fiji, P. polystachion yielded 11-13 t/ha per year of DM when fertilized with N. Steers grazing unfertilized P. polystachion in Fiji produced liveweight gains of only 110-80 kg per beast per year within a stocking rate range of 1-3 beasts/ha. Seed yields of up to 420 kg/ha have been obtained in India. Seeds can be viviparous in very wet weather.

Genetic resources and breeding

It is unlikely that substantial germplasm collections are being maintained and there are no breeding programmes with P. polystachion .

Prospects

P. polystachion 's ability to adapt, persist, give high yields, and combine with a range of legumes make this a very useful grass. Research is needed into its general agronomy, the best management regime to obtain the highest animal production, and how to conserve it as hay or silage.

Literature

• Baki, B.B., Latiff, A. & Ahmad Puat, N., 1989. The genus Pennisetum in Peninsular Malaysia with particular reference to P. setosum, a new record for the weed flora. Proceedings Symposium on weed management, 7-9 June 1989, Bogor, Indonesia.
• Bogdan, A.V., 1977. Tropical grasses and fodder plants. Longman, London. pp. 231-232.
• Brunken, J.N., 1979. Morphometric variation and the classification of Pennisetum section Brevivalvula (Gramineae) in tropical Africa. Botanical Journal of the Linnean Society 79: 51-64.
• Häfliger, E. & Scholz, H., 1980. Grass weeds 1. Ciba-Geigy Ltd., Basel, Switzerland. p. 142.
• Holm, L.G., Plucknett, D.L., Pancho, J.V. & Herberger, J.P., 1977. The world's worst weeds: distribution and biology. The East-West Center, University of Hawaii Press, Honolulu, Hawaii, United States. pp. 367-371.
• Manidool, C., 1977. Nutritive values of ya kachonchop (Pennisetum polystachion) [in Thai]. Poultry Magazine, Poultry Promotion Association of Thailand 25: 1.
• Partridge, I.J., 1986. Effect of stocking rate and superphosphate level on an oversown fire climax grassland of mission grass (Pennisetum polystachion) in Fiji. Tropical Grasslands 20: 166-180.
• Skerman, P.J. & Riveros, F., 1990. Tropical grasses. FAO, Rome. pp. 616-620.

Authors

B.B. Baki, C. Manidool & C.P. Chen