Prota 1: Cereals and pulses/Céréales et légumes secs
Ess. Agrostogr.: 53, 161, 171 (1812).
2n = 18, 36, 54, 63, 72, 108, 126
Echinochloa scabra (Lam.) Roem. & Schult. (1817).
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.
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.
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.
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.
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.
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.
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.
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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.