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Pennisetum purpureum K. Schumach.

Poaceae
Elephantgrass, Napier grass, Uganda grass

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 unpublished.


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

Uses

This is one of the highest yielding tropical forage grasses. In Malawi it is considered as a cut-and-carry forage for stall feeder systems. In areas where adapted, grown for green feed, silage and rotational grazing. Its stemmy nature limits its usefulness for grazing purposes, as animals selectively eat leafy portions and leave stems behind. Said to equal bamboo for paper making. It has been used to suppress Imperata cylindrica in the Philippines. Venkatesh and Shetty (1978) found the growth rate of grasscarp fed hybrid Napier grass was three times the rate of those fed Hydrilla verticillata and five times Ceratophyllum demersum. Reported as a weed in nine crops in 25 countries (Holm et al, 1977).

Folk Medicine

In Spanish Guinea the leaf and stalk infusion is used as a duiretic in anuria or oliguria. In Central Africa, used as a source of a medicinal salt (Watt and Breyer-Brandwijk, 1962).

Chemistry

Per 100 g, the hay is reported to contain 10.9 g H2O, 8.2 g protein, 1.8 g fat, 68.6 g total carbohydrate, 34.0 g fiber and 20.5 g ash. Silage contains 5.8 g protein, 4.9 g fat, 73.4 g total carbohydrate, and 15.9 g ash. Fresh grass contains 77.8 g water, 1.0 g protein, 0.5 g fat, 17.6 g total carbohydrate, 3.1 g ash, 0.12% Ca and 0.07% P. Green fodder contains calcium, 0.12; phosphorus, 0.07; potassium, 0.80; sodium, 0.10; magnesium, 0.06; iron, 0.021; sulphur, 0.03; and silicon, 0.57%. It is a good source of carotene (182–221 mg/g) and tocopherol (195-260 mg/g). Napier grass meal was as effective in maintaining the growth of the birds as lucern meal. A nutritious silage, highly palatable to animals, can be prepared after adding molasses (2%) and salt (0.8%) (C.S.I.R., 1948-1976). Gutierrez and de Faria (1979) determined that the main free sugars were glucose, sucrose, and fructose, with fructose content always higher than glucose.

Toxicity

Seiler et al. (1979) report fatal nitrate poisonings in cattle whose diet consisted solely of Napier grass. Levels of nitrate averaged 28.3 mg/g with some samples as high as 44 mg which levels in the same species from non-toxic areas was 3.9 mg/g.

Description

Tall, tufted, rhizomatous perennial, very coarse and robust, in dense clumps; culms 2–7 m tall; leaves large, 30–90 cm long, up to 3 cm broad, elongate; flat; panicles dense, usually more than 15 cm long, stiff, tawny or purplish; fascicles sessile, the sparsely plumose bristles exceeding the 2 or 3 unequally pedicelled spikelets; grain permanently enclosed in the lemma and palea; spikelets not wore than 7 mm long. 4x = 28; 8x = 56; 2n = 27. Seeds 3,091,410/kg.

Germplasm

Many cultivars of elephantgrass have been developed in tropical countries, as in Brazil (16 vars.), Malawi, Cameroons, Congo and Gold Coast. "Merkergrass" has a more blue green color. Merker can bloom 60 days after planting and reseeds itself occasionally. Bogden mentions Capricorn, Cubano, Domira, Ghana, Gold Coast, Merker, Merkeron, Mineiro, Napier, Pungwe, Uganda, and Urukwanu as noteworthy cultivars. In Brazil, e.g. 'Mineiro' yielded 21.4 and 30.0 MT/ha in two rainy seasons and 3.3 and 6.0 MT/ha in two dry seasons during two years, outyielding the other 11 cultivars studied. Reported from the African Center of Diversity, elephantgrass or cvs thereof is reported to tolerate drought, fire, frost, fungi, high pH, laterites, low pH, monsoon, savanna, sewage sludge, virus, weeds, and waterlogging (Duke, 1978). Pusa Giant Napier, an Indian cv, is said to be more nutritious, succulent, palatable and responsive to N than Napier Grass. It is said to have yielded 279 MT fodder/ha, cf 135 for Napier (C.S.I.R., 1948–1976). (2n = 28, 27, 56)

Distribution

Native to tropical Africa. Introduced to South America, Puerto Rico, Philippine Islands, Hawaii and southern United States.

Ecology

Requires a rich soil for best growth. It does not tolerate much frost, so culture is limited to warmest parts of mainland United States and Hawaii. The herbage is killed by frost but soil must be frozen to kill the rhizome. Thriving on poorly drained soils to dry sandy soils, it grows best in rich well-drained soils. In Uganda, napier grasslands are considered the fire subclimax to evergreen forest. Ranging from Warm Temperate Dry to Wet through Tropical Dry to Wet Forest Life Zones, elephantgrass is reported to tolerate annual precipitation of 2.0 to 40.0 dm (mean of 34 cases = 16.5) annual temperature of 13.6 to 27.3°C (mean of 34 cases = 23.0) and pH of 4.5 to 8.2 (mean of 28 cases = 6.2). (Duke, 1978, 1979)

Cultivation

Usually propagated vegetatively; if grown from seed, it is started in a nursery and transplanted. To control weeds at the first stages of establishment, inter-row cultivation and herbicides can be used; in Cuba 6 kg atrazine/ha was a more effective herbicide (Bogdan, 1977). It is grown in rows and cultivated for highest yields. Fertilizer of 100–150 kg/ha of N after each harvest gives best uniform production, with total of 900 kg/ha of N for six harvests. Potential carrying capacity of Napier grass is very high with application of 50 kg/ha of N after each harvest, thus maintaining about 27 head/ha.

Harvesting

Feeding whole or chopped at 45 day regrowth had no effect on digestibility of all nutrients, but wilting increased the digestibility of dry matter, crude protein and crude fiber; also digestibility of N-free extract and gross energy were significantly higher for wilted than for fresh grass. These factors were increased in 60 day regrowth.

Yields and Economics

In some of the referenced studies, dry matter forage yields range from 27.3 to 37.1 MT/ha in regions with over 125 cm rainfall year. Yield of dry matter increased with advancing maturity, with average yields of 4.85 and 7.27 MT/ha at 45 and 60 day regrowth intervals, respectively. Average yield of unfertilized grass during the wet season ranges from 3.2–5.3 MT/ha, and for dry season, from 2.4–4.4 MT/ha, with range of age of 42–63 days. Yields of crude protein range from 403.55 to 487.09 kg/ha for 45 and 60 days cutting intervals, respectively. Yields are higher under longer than shorter photoperiods. Summarizing several previous studies, Bogdan (1977) concludes that yields in farm practice are more likely to be 2–10 MT/DM/ha/yr for low or no fertilizers and 6–30 for well fertilized farms, not the illustrious 85 MT one finds under optimum conditions.

Energy

According to the phytomass files (Duke, 1981b), annual productivity ranges from 2 to 85 MT/ha. Miyagi (1980) obtained annual yields as high as 500 MT WM/ha and 70 MT DM, spacing the plants 50 x 50 cm, outdoing the high reported by Bogdan (1977) at 310 MT WM. Some of the higher DM yields reported are 19 MT/ha in Australia, 66 in Brazil, 58 in Costa Rica, 85 in El Salvador, 48 in Kenya, 14 in Malawi, 64 in Pakistan, 84 in Puerto Rico, 76 in Thailand, and 30 in Uganda (Duke, 1981b). Stems of elephant grass are primarily lignocellulose with virtually no juice sugars. High N is required for high biomass yields. Experimental yields in Queensland, Australia, have attained 70 MT DM/ha/yr of which 50 are stem. Expected farm yields might be 50–55 MT DM, while the best sugarcane yields are about 50 in north Queensland. Stewart et al. (1979) identified no other advantage of elephant grass over sugarcane as an energy crop. Pennisetum americanum is reported to yield 1–22 MT/ha/yr, P. clandestinum 2–25, P. pedicellatum 3–8, P. polystachyion 3–10 (Duke, 1981b).

Biotic Factors

Following fungi have been reported on Elephantgrass: Aegerita penniseti, Apiospora camptospora, Armillaria mellea, Beniowskia pennisetae, B. sphaeroidea, Cercospora fusimaculans, C. penniseti, C. sorghii, Didymosphaeria panici, Gloeocerospora sorghii, Helminthosporium ocellum, H. sacchari, Lacellinopsis spiralis, Leptosphaeria penniseti, L. penniseticola, Myrothecium gramineum, M. striatisporum, Nigrospora oryzae, Periconia sacchari, Phyllachora penniseti, Piricularia grisea, Puccinia penniceti, Sclerospora graminicola, Septoria penniseti and Stagonospora penniseti. It is also attacked by the bacterium, Pectobacterium carotovorum, and several diseases as Pseudo-Fiji Disease, Chlorotic streak, a disease of sugarcane, and leaf mottle virus. Elephantgrass is also attacked by the following nematodes: Aphelenchus avenae, Meloidogyne incognita acrita, M. javanica and Pratylenchus brachyurus.(Golden, p.c., 1984) Pennisetum purpureum is an alternate host of Cassytha filiformis L., Helminthosporium sacchari, Leptosphaeria sacchari, Meloidogyne sp. and Phyllosticta sp. (Holm et al, 1977).

References

Complete list of references for Duke, Handbook of Energy Crops
Last update Wednesday, January 7, 1998 by aw