Pennisetum purpureum (PROSEA)
Pennisetum purpureum Schumach.
- Protologue: Beskr. Guin. Pl.: 44 (1827).
- Family: Gramineae
- Chromosome number: 2n= 28, 56, 27
- Elephant grass, napier grass (En). Herbe d'éléphant (Fr)
- Indonesia: rumput gajah
- Malaysia: rumput gajah
- Philippines: buntot-pusa (Tagalog), handalawi (Bokil), lagoli (Bagobo)
- Thailand: ya-nepia
- Vietnam: co' duôi voi.
Origin and geographic distribution
Of tropical African origin, this grass has been introduced to all tropical regions of the world and is naturalized throughout South-East Asia where annual rainfall exceeds 1000 mm and there is no long dry season.
The main use of elephant grass is as a forage for ruminants. As a naturalized species in humid regions of South-East Asia, it is collected by farmers by cutting the whole plant, which is offered to ruminants, mainly buffaloes and cattle, which are either tethered or confined in stalls. It can also be used to provide mulch.
The feeding value is influenced mainly by the ratio of leaf to stem and by age. Nitrogen concentrations of regularly harvested forage are usually in the range of 2-4%. Young leaves may have a digestibility of 70%, but this value declines rapidly with age to less than 55%. Stems are of low digestibility, except when very young.
A tall, robust, deep-rooting, erect perennial, with short rhizomes. Stem up to 7 m tall and 3 cm in diameter, up to 20-noded. The plant forms clumps to 1 m across. Leaf-sheath glabrous to short bristly; leaf-blade linear with broad base and acute tip, up to 120 cm × 5 cm, glabrous to hairy at the base, with a prominent midrib along the lower surface. Inflorescence a dense spike-like panicle, up to 30 cm tall and 30 mm wide, not including the 16-40 mm long bristles on the spikelets; spikelets 5-7 mm long, solitary or in clusters of up to five, of which usually only one is fertile; the lower floret is male or void, the upper bisexual and fertile, sometimes male. There is little or no seed formation.
Growth and development
Elephant grass is an obligate quantitative short-day plant, with a critical photoperiod between 13 and 12 hours. However, viability of pollen is poor and this may be the main cause of the typically poor seed set. In addition, seedlings are weak and grow slowly, so that the grass is usually propagated vegetatively. Under favourable conditions, vegetative material is fast-growing and the plant can reach a height of several metres within two months.
Other botanical information
There are numerous cultivar names in various countries and three subspecies have been proposed in northern Africa, but there has been no similar subdivision for South-East Asia. In Florida (United States), a dwarf cultivar "Mott" of high feed value has been developed.
Elephant grass is adapted to a humid warm environment. However, it can exhibit remarkable drought-tolerance and can survive light frost. For acceptable agronomic performance, the species requires a deep soil of at least moderate fertility, although it will survive at much reduced productivity on all kinds of soils. It does not tolerate sustained flooding. In its naturalized state, the grass is found mainly along forest edges.
Propagation and planting
Vegetative propagation is either by dividing clumps of roots and stubble, or by stem cuttings consisting of at least three nodes, two of which are buried. This can be done by hand or with a sugar-cane planter. Row width ranges from 50-200 cm, the greater distances being preferred in drier regions. Distance within rows varies from 50-100 cm. Intercropping with cassava and banana is often practised in home gardens.
For high yields and persistence, elephant grass planted as a crop requires a regular water supply and a rich supply of nutrients. The latter applies particularly when the crop is cut frequently. Nutrient removal per t DM is: N 10-30 kg, P 2-3 kg, K 30- 50 kg, Ca 3-6 kg, Mg and S 2-3 kg. With annual DM yields between 20 and 40 t/ha, very large quantities are thus extracted from the soil. If they are not replenished, yield soon drops and weeds will invade. Although elephant grass is not often grown with legumes, it combines well with, for instance, Centrosema pubescens Benth. and it can be interspaced with the shrub legume Leucaena leucocephala (Lamk) de Wit.
Diseases and pests
The most common disease is a blight caused by Helminthosporium sacchari . The best control measure is to use a resistant cultivar. No major pests have been recorded.
Elephant grass can be harvested year-round. It is usually offered fresh to animals, but it can also be conserved as silage. However, preservation is often poor and losses of DM and crude protein can be very large. Best results are obtained by chopping the material, mixing it with molasses, and compressing and covering it to exclude air.
Annual DM yields that can be expected in farm practice may range from 2-10 t/ha for unfertilized or slightly fertilized stands and from 6-40 t/ha from grass well fertilized with N and given a basic dressing of P.
Cattle liveweight gains of 1 kg/animal per day during the growing season and of 120 kg/animal and 480 kg/ha per year over 3 years were recorded on N fertilized dwarf elephant grass ("Mott") in Florida, United States.
Because of clonal propagation, planted stands of P. purpureum are often uniform. However, the species contains much variation in the extent of hairiness of stem nodes and leaf-sheaths, and the size, colour and density of the panicle. There are also differences in stem thickness and height and leaf size between forms of the grass, but these are greatly influenced by the fertility of the soil and by rates of fertilizers.
P. purpureum × P. americanum (L.) Leeke hybrids have been developed in many countries. They produce larger plants with more tillering and larger total production. However, this also means that more mineral nutrients are required. The hybrid is sterile and therefore must be vegetatively propagated.
Elephant grass is widely grown in tropical regions and, with adequate use of fertilizers, large increases in yield can be expected. By harvesting at a young stage of growth or by using dwarf cultivars, forage of high feeding value can be obtained. An advantage of this species is its versatility. It can be grown on a large or small scale; it lends itself to mechanization but is also suitable for smallholder agriculture.
- Bodgan, A.V., 1977. Tropical pasture and fodder plants. Longman, London. pp. 233-243.
- Crowder, L.V. & Chheda, H.R., 1982. Tropical grassland husbandry. Longman, London. 562 pp.
- Skerman, P.J. & Riveros, F., 1990. Tropical grasses. FAO, Rome. pp. 621-627.
- Sollenberger, L.E. & Jones, C.S., 1989. Beef production from nitrogen-fertilized Mott dwarf elephant grass and Pensacola bahiagrass pastures. Tropical Grasslands 23: 129-134.
L. 't Mannetje