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Echinochloa stagnina (Retz.) P.Beauv.

Protologue
Ess. Agrostogr.: 53, 161, 171 (1812).
Family
Poaceae (Gramineae)
Chromosome number
2n = 18, 36, 54, 63, 72, 108, 126
Synonyms
Echinochloa scabra (Lam.) Roem. & Schult. (1817).
Vernacular names
Hippo grass, long-awned water grass, burgu grass (En). Bourgou, roseau sucré, roseau à miel du Niger (Fr).
Origin and geographic distribution
Echinochloa stagnina occurs throughout tropical Africa and is also found in tropical Asia, where it has possibly been introduced. Occasionally, it is naturalized in other tropical regions.
Uses
In tropical Africa the grains of Echinochloa stagnina are traditionally collected as a cereal, especially in times of food shortage. Echinochloa stagnina is sown as a cereal in India. The sweet stems and rhizomes have been used to produce alcoholic or non-alcoholic beverages and are still used for the extraction of sugar for making confectionery and liqueurs. Children suck the stems for the sugar. Grasslands of Echinochloa stagnina (‘bourgoutières’) are important dry-season grazing areas for the herds of pastoralists in West Africa. In Chad Echinochloa stagnina is sown to improve pastures; it is also sown as a fodder grass in Egypt. It can be made into hay. The stems are used for thatching and mat-making, and the leaves for caulking boats. The ash of burnt leaves has been used in the manufacture of soap and as a mordant with indigo dye.
Properties
Echinochloa stagnina plants in mid-bloom in Niger contain crude protein 11.3%, crude fibre 32.5%, crude fat 2.2%, nitrogen-free extracts 44.2%, Ca 0.31%, Mg 0.31% and P 0.25%. The pith of the culms contains 10% saccharose and 7–8% reducing sugars. Because of its high sugar content Echinochloa stagnina is considered an excellent fodder grass.
Botany
Perennial aquatic grass up to 2.5 m tall, or taller (up to 10 m) when floating, with stout, often floating rhizomes; stem (culm) decumbent, with a diameter up to 2.5 cm, often spongy, rooting and branching at the lower nodes. Leaves alternate, simple and entire; leaf sheath 15–25 cm long, glabrous or rarely hairy, loose at base of plant; ligule a line of hairs, often absent in upper leaves; blade linear, 10–60 cm × 0.5–3 cm, firm, with scabrid margin and filiform tip. Inflorescence composed of racemes along a central axis 6–35 cm long, erect or nodding; racemes up to 15 cm long, closely overlapping or distant, with spikelets in pairs. Spikelets narrowly ovate, 3.5–6 mm × 1–2 mm, slightly hairy but with prickly hairs on the veins, 2-flowered with lower floret male or sterile and upper bisexual; lower glume c. ½ of spikelet length, sharply acuminate to mucronate, upper glume as long as spikelet, awnless or with an awn up to 4 mm long; lemma of lower floret with a stout awn up to 25(–50) mm long, lemma of upper floret 3–5 mm long; stamens 3, anthers violet; ovary superior, stigmas 2. Fruit a caryopsis (grain).
Echinochloa comprises 30–40 species. It is a taxonomically difficult genus, because clear-cut boundaries between the species seldom exist and the species are very variable. Introgression between species is common. Echinochloa stagnina is extremely variable.
Stem elongation enables Echinochloa stagnina to support a water level increase of 4 cm per day, and it can be found in water depths of up to 4 m. In the central Niger delta the biomass accumulated in the flooding season can be as high as 15–30(–40) t dry matter per ha. Stems trampled by animals and covered by soil form roots at the nodes, which is an important mode of natural regeneration of Echinochloa stagnina. Echinochloa stagnina is self-pollinating. It follows the C4-cycle photosynthetic pathway.
Ecology
In tropical Africa Echinochloa stagnina occurs from sea-level up to 2300 m altitude, in shallow water, swamps and on periodically inundated clay soils. It often forms large floating mats, rooting in the mud. Echinochloa stagnina is frequently the dominant species of the natural flood-plain grasslands in the central Niger delta and the shores of Lake Chad. It may occur in massive, nearly pure stands or together with Echinochloa colona (L.) Link, Echinochloa pyramidalis (Lam.) Hitchc. & Chase and Oryza longistaminata A.Chev. & Roehr.
Echinochloa stagnina is an important weed of rice in tropical Africa, the Indian subcontinent and Thailand, sometimes obstructing waterways.
Management
Echinochloa stagnina is propagated by seed, stem cuttings or plant division. The 1000-seed weight is about 2.4 g. Under natural conditions the seeds are shed in water. In experiments, seeds stored under water in the dark at a temperature of 20°C showed no dormancy and had a germination percentage of almost 100%, whereas seeds kept under dry conditions had a dormancy period of 6–7 months. The dormancy is broken by removing the glumes, but this results in rapidly reduced viability. Seeds germinate within a week after sowing. In regeneration programmes in Mali seedlings or rooted cuttings are planted out into the field at densities of 10,000–16,000 plants/ha.
In the central Niger delta in Mali the grains of Echinochloa stagnina are traditionally harvested using boats and by beating the inflorescences over a net. As the grains shatter easily, they are harvested at an early stage. To obtain sugar, the harvested plants are traditionally dried in the sun, after which the leaves are burnt off. The stems are washed and ground, and sugar is extracted from them by filtrating with warm water. Vegetative material for forage is cut using boats, and is eaten green or as hay. The forage is not only used locally, but also traded commercially, with an important market in Tombouctou. After the water has receded, animals are allowed to graze on the remaining plant material until the end of the dry season.
Genetic resources and breeding
Around 100 years ago, the ‘bourgou’ area in the central Niger delta was estimated at about 250,000 ha, but since then much has been replaced by rice fields. Around 1970 the area was estimated at 8000–10,000 ha. Since 1970 further reduction has taken place due to rice cultivation, reduced rainfall, reduced water levels in the river, overharvesting and overgrazing, resulting in a disturbance of traditional pastoral systems. The International Livestock Research Institute (ILRI), Addis Ababa, Ethiopia, holds 9 accessions of Echinochloa stagnina.
Prospects
Echinochloa stagnina is a useful multipurpose plant in semi-arid regions of West Africa, especially in the central delta of the Niger river. Its area and importance have declined due to various factors, and this trend will be difficult to reverse. In many other regions Echinochloa stagnina is considered a weed, and therefore it does not seem advisable to promote it elsewhere. Information is lacking on the nutritional quality of the grain.
Major references
• Bonis Charancle, J.-M., 1994. Gestion des ressources naturelles: la régéneration des bourgoutières dans la boucle du Niger au Mali. Revue d’Elevage et de Médecine Vétérinaire des Pays Tropicaux 47(4): 425–434.
• Burkill, H.M., 1994. The useful plants of West Tropical Africa. 2nd Edition. Volume 2, Families E–I. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 636 pp.
• François, J., Rivas, A. & Compère, R., 1989. Le pâturage semi-aquatique à Echinochloa stagnina (Retz.) P.Beauv. Etude approfondie de la plante ‘bourgou’ et des bourgoutières situées en zone lacustre du Mali. Bulletin des Recherches Agronomiques de Gembloux 24(2): 145–189.
• Harlan, J.R., 1989. Wild grass seed harvesting in the Sahara and sub Sahara of Africa. In: Harris, D.R. & Hillman, G.C. (Editors). Foraging and farming: the evolution of plant exploitation. Unwin Hyman, London, United Kingdom. pp. 79–98.
• Phillips, S., 1995. Poaceae (Gramineae). In: Hedberg, I. & Edwards, S. (Editors). Flora of Ethiopia and Eritrea. Volume 7. Poaceae (Gramineae). The National Herbarium, Addis Ababa University, Addis Ababa, Ethiopia and Department of Systematic Botany, Uppsala University, Uppsala, Sweden. 420 pp.
Other references
• Bartha, R., 1970. Fodder plants in the Sahel zone of Africa. Weltforum Verlag, München, Germany. 306 pp.
• Busson, F., 1965. Plantes alimentaires de l’ouest Africain: étude botanique, biologique et chimique. Leconte, Marseille, France. 568 pp.
• Clayton, W.D., 1989. Gramineae (Paniceae, Isachneae and Arundinelleae). In: Launert, E. & Pope, G.V. (Editors). Flora Zambesiaca. Volume 10, part 3. Flora Zambesiaca Managing Committee, London, United Kingdom. 231 pp.
• François, J., Rivas, A., Hellemans, P. & Compere, R., 1991. Régéneration des bourgoutières en zone lacustre du Mali par semis en décrue, technique basée sur des études agrométéorologiques et écophysiologiques. Bulletin des Recherches Agronomiques de Gembloux 26(1): 169–181.
• Gibbs Russell, G.E., Watson, L., Koekemoer, M., Smook, L., Barker, N.P., Anderson, H.M. & Dallwitz, M.J., 1990. Grasses of Southern Africa: an identification manual with keys, descriptions, distributions, classification and automated identification and information retrieval from computerized data. Memoirs of the Botanical Survey of South Africa No 58. National Botanic Gardens / Botanical Research Institute, Pretoria, South Africa. 437 pp.
• Hanelt, P. & Institute of Plant Genetics and Crop Plant Research (Editors), 2001. Mansfeld’s encyclopedia of agricultural and horticultural crops (except ornamentals). 1st English edition. Springer Verlag, Berlin, Germany. 3645 pp.
• McKenzie, P.M., Michael, P.W., Urbatsch, L.E., Noble, R.E. & Proctor, G.R., 1993. First record of Echinochloa stagnina (Poaceae) for Puerto Rico and key to the Echinochloa in the West Indies. SIDA 15(3): 527–532.
• van der Zon, A.P.M., 1992. Graminées du Cameroun. Volume 2, Flore. Wageningen Agricultural University Papers 92–1. Wageningen Agricultural University, Wageningen, Netherlands. 557 pp.
• Yabuno, T., 1968. Biosystematic studies of Echinochloa stagnina (Retz.) P. Beauv. and Echinochloa pyramidalis (Lamk.) Hitchc. et Chase. Cytologia 33(3–4): 508–519.
• Yabuno, T., 1983. Biology of Echinochloa species. In: Proceedings of the Conference on Weed Control in Rice, 31 August – 4 September 1981. IRRI, Los Baños, Philippines. pp. 307–318.
Author(s)
M. Brink
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands


Editors
M. Brink
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
G. Belay
Ethiopian Agricultural Research Organization, Debre Zeit Center, P.O. Box 32, Debre Zeit, Ethiopia
Associate editors
J.M.J. de Wet
Department of Crop Sciences, Urbana-Champaign, Turner Hall, 1102 South Goodwin Avenue, Urbana, IL 61801, United States
O.T. Edje
Faculty of Agriculture, University of Swaziland, P.O. Luyengo, Luyengo, Swaziland
E. Westphal
Ritzema Bosweg 13, 6706 BB Wageningen, Netherlands
General editors
R.H.M.J. Lemmens
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
L.P.A. Oyen
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
Photo editor
A. de Ruijter
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article:
Brink, M., 2006. Echinochloa stagnina (Retz.) P.Beauv. In: Brink, M. & Belay, G. (Editors). PROTA 1: Cereals and pulses/Céréales et légumes secs. [CD-Rom]. PROTA, Wageningen, Netherlands.