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Andropogon gayanus Kunth

Poaceae
Gamba grass

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 unpublished.

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

Uses

Considered one of the best grazing grasses in northern Nigeria and northern Ghana. Makes valuable hay and green fodder grass in central and northeastern Brazil. In Africa, this grass grows in large tufts up to 2 m tall. Young shoots are preferred, but cattle will eat it up to time of flowering. Stems, flattened, are used for coarse matting (weaving grass mats and thatching). Plants are useful for planting on banks for erosion control.

Folk Medicine

No data uncovered.

Chemistry

On a zero moisture basis, fresh Ghanan grass (19.9% DM) contains 12.9% CP, 25.6% CF, and 8.5% ash; the same (24 weeks old) (59.4% DM) contains 5.4% CP, 29.9% CF, and 5.5 % ash. Nigerian hay (88.5% DM) contains 6.1% CP, 35.1% CF, 7.9% ash, 1.7% EE, and 49.2% NFE, while silage (DM 25.0%) contains 5.8% CP, 37.4% CF, 7.4% ash, 1.9% EE, and 47.5% NFE (Gohl, 1981).

Description

Tall annual or perennial, tussock grass; culms erect, up to 3 m tall, more or less stout, about 0.6 cm in diameter, glabrous, many-noded, producing flowering branches from the third node upward; leaves glabrous or softly pubescent, rarely villous or tomentose; sheath tight, striate; ligule short, rounded or truncate, glabrous or somewhat hairy on back, rarely exceeding 0.2 cm long; lamina linear to lanceolate-linear in the lower leaves, usually from a much attenuated base and there often forming a terete petiole, tapering to a fine point, over 30 cm long, up to 1.6 cm broad, glaucescent or reddish, margin scabrous; inflorescence in panicles up to 6 or more primary mixed 2 to many rayed tiers, the inner ray of lower or lowest tiers often up to 30 cm long (sometimes up to 60 cm long), with 2–4 secondary few-rayed tiers; spatheoles pale green, herbaceous, lanceolate-oblong, 6.5–7.5 cm long, at length more or less tightly enrolled and turning red; racemes in pairs, 3.5–6.5 cm long, one sessile, the other with a bare base about 0.4 cm long, joints stout, cuneate-clubshaped; sessile spikelets greenish or tipped brown or red, about 0.8 cm long including the obtuse callus; scantily bearded at base; glumes equal; awn 1.3–2.2 cm long, twisted well below middle, column brown, bristle pale; pedicellate spikelets male and glabrous. Fl. April–June in tropical Africa.

Germplasm

Several varieties are recognized: var. gayaunus with pedicelled spikelets glabrous, the joints and pedicles ciliate on one margin only; var. squamulatus, with pedicelled spikelets scaberulous, the joints and pedicels ciliate on both margins; var. argyophoeus, with pedicelled spikelets plumosely villous, basal leaves villous; var. bisquamulatus, with pedicelled spikelets not so hairy, basal leaves not villous. Squamulatus and bisquamulatus are "dry ground" varieties which grow best on well-drained sandy clays of medium to high fertility (Bowden, 1963). Reported from the Africa Center of Diversity, gamba grass or cvs thereof is reported to tolerate drought, fire, frost, high pH, heavy soil, low pH, poor soil, savanna, slope, and waterlogging. Var. gayanus is more likely to tolerate waterlogging and frosts than the "dry-land" varieties (Duke, 1978). (2n = 20, 40, 44)

Distribution

Native and widely distributed in tropical Africa, north and south of Equator; introduced to other tropical areas, as tropical Queensland, Brazil, India, and western Australia.

Ecology

Ranging from Warm Temperate Moist through Tropical Dry to Wet Forest Life Zones, gamba grass is reported to tolerate annual, precipitation of 8 to 27 dm (mean of 9 cases = 12.2), annual temperature of 15 to 32°C (mean of 9 cases 21.4), and pH of 4.3 to 8.3 (mean of 5 cases = 6.1). In grassy places, damp places, low-lying meadows, edge of thickets; often forming large areas. Also thrives in areas with long dry season up to 7 months long. Adapted to a wide range of soil types, with different ecotypes adapted to various soils varying from sandy to heavy black cracking clays. Very drought resistant and not to susceptible to frost.

Cultivation

Propagated by seed. Caryopses germinate better with chaff removed and covered over by soil or sand. Clean seedbed required, but sowing should not be delayed more than 2 months after beginning of rains (in India). It is often under-sown in corn, sesame or millet. Seeding rate varies: in Brazil, 5 kg/ha; in Nigeria, 35–70 kg/ha, of uncleaned seed. Seed production is often very low. Sometimes grown in mixture with Clitoria ternatea in tropical Australia. May also be propagated by splints, those from mature woody stumps doing best (Bowden, 1963). Highest return of dry matter per unit N (14.4 kg DM/kg N) occurred at 28 kg N/ha; CP content increased only modestly as N was increased, reaching a maximum 10.5% with the highest N level. At higher levels of N, A. gayanus was replaced by less desirable grasses (Haggar, 1974). Bogdan (1977) reports trebling of yields with 100 kg N/ha and double to treble with 20 MT fym/ha.

Harvesting

Plants persist well under grazing, but are only palatable before flowering. The flowering stems, which are produced in quantity, are hard and should be removed by mowing or burning. Frequent burning tends to suppress this grass and allows it to be replaced by less useful species. In one experiment (Bowden, 1963) over three years, plots were cut only when grass reached 6, 9, 12 and 15 dm, necessitating 12, 9, 8 and 7 cuts respectively. The taller the grass when cut, the higher the annual DM yield. Plants grown in rows gave more DM, CP and soluble carbohydrate than plants grown in swards.

Yields and Economics

Haggar (1974) reported yields of 2–7 MT in 1964, 10–12 in 1965, and 6–12 in 1966, at 0 to ca 200 kg/N/ha respectively. According to Bogdan (1977), this is one of the high yielding grasses of West Africa, being outyielded by Melinis minutiflora, Panicum maximum and/or Pennisetum purpureum. Fresh fodder yield of 57 MT are recorded from India, 76 from Mali. From the Cameroons, DM yields of 7.1–7.8 MT/ha, 4 MT/DM from Australia, and 2.4–8.6 MT elsewhere (Bogdan, 1977). Seed yields up to 30 kg/ha per cut with 3 cuts per year have been recorded in Brazil. In pure stands in Ghana, dry matter yields per harvest from March 12 to November 12 (in 5 harvests) averages 7,478 kg/ha, with total harvest being 37,391.35 kg/ha. In Andropogon-Desmodium stands 34,334 kg/ha; in Andropogon-Centrosema, 30,397.45 kg/ha (Tetteh, 1972). Widely cultivated and used grass used in tropical Africa (Nigeria and Ghana), Brazil, India, and Australia for fodder, grazing, hay and to some extent for erosion control.

Energy

According to the phytomass files (Duke, 1981b), annual productivity ranges from 4 to 25 MT/ha. According to Gohl, the ME (metabolizable energy) for cattle ranges from 1.71 megacalories/kg DM in silage to 1.65 in hay, 2.02 in mature forage and 2.33 in early vegetative forage.

Biotic Factors

Following fungi have been reported on this grass: Fusarium moniliforme (on seed), Phyllachora assimilis, Puccinia erythraeensis, P. versicolor, Sphacelotheca andropogonis, S. ischaemicola. Nematodes isolated from this grass include: Criconemella sp., Helicotylenchus cavenessi, R. pseudorobustus, Memicriconemoides cocophilus, Hemicycliophora oostenbrinki, Scutellonema clathricaudatum, Tylenchorhynchus annulatus, Xiphinema ebriense, and X. nigeriense.

References

Complete list of references for Duke, Handbook of Energy Crops
Last update December 22, 1997