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Description
A perennial species which in Africa grows in large tufts up to 2 m high with a reedlike
habit. It is blue, with a waxy bloom. The leaves are distinctive because the many blades
appear to be petioled. In the lowest leaves the laminar tissue is greatly reduced, almost
to the midrib, above the ligule. The leaf widens gradually and then narrows again, so that
the blade is finely pointed (Chippendall & Crook, 1976). Fifty percent of its roots
are fibrous, and less than 0.5 mm in diameter, growing laterally at an angle of 10-15° to
the surface for the first 50 cm, and then growing parallel to the surface for 1 m. These
collect the early falls of rain. Forty percent are cord roots up to 2 mm in diameter which
grow downwards at 30-40° and rarely measure 50 cm long. Ten percent of the roots are 0.5
mm in diameter, branch rarely, and form ropes. These grow vertically down to 80 cm and
give drought tolerance (Bowden, 1963a).#
Distribution
Native to tropical Africa and now introduced to many countries.
Season of growth
Summer.
Altitude range
Sea level to 2 000 m, but grows best below 1 000 m.
Rainfall requirements
It grows in the 400-1 400 mm rainfall regime but prefers a rainfall of 750-1 260 mm and
more than three months dry season up to six months.
Drought tolerance
Excellent. Ten percent of its roots form ropes 0.5 mm thick which go down to more than
80 cm (Bowden, 1963a). In an oxisol at Carimagua, Colombia it dried the profile to 120 cm
(CIAT, 1978).
Soil requirements
It will grow on a wide range of soils including those of low fertility, from sands to
black cracking clays, but prefers sandy clays of medium to high fertility. In South
America it has shown outstanding results in oxisol-ultisol soils (CIAT, 1978). In the
Sudan it is common on sandy loams to loamy sands.
Ability to spread naturally
It spreads slowly by seed.
Land preparation for establishment
A clean, firm seed-bed is required.
Sowing methods
Cleaned and de-bearded seed is drilled in shallow rows or broadcast and rolled. It can
be planted also from root-stocks (splits), the best being mature woody stumps.
Sowing depth and cover
Sow seed at 1-2.5 cm below the surface.
Sowing time and rate
Sow at the beginning of the rainy season at 5 kg/ha (35-70 kg/ha uncleaned).
Seed treatment before planting
De-beard the seed a machine has been developed at CIAT, Colombia (CIAT, 1978).
Seedling vigour
Good.
Vigour of growth and growth rhythm
Dry-matter yield increased during the wet season from June to October in Nigeria,
reaching a maximum of about 3 800 kg/ha in October, declining then until February. Cutting
in early October gave best balance of bulk and quality (Haggar, 1970).
Response to defoliation
At Fashola Livestock Farm, Nigeria, A. gayanus required intervals of more than six
weeks between cuttings, and a cutting height of about 4 cm to maintain productivity and a
good stand (Ahlgren et al., 1959). It cannot stand heavy grazing until it is well
established, but requires high stocking rates to maintain reasonable height.
Grazing management
It should be utilized when young, as once flowering stems appear it becomes harsh and
of little nutritional value. Burning during the dry season is universal. However, it is
important to maintain some residual dry matter and leaf area after grazing in such erect
grasses (CIAT, 1978).
Response to fire
It tolerates fire and in Ghana and elsewhere it is burnt every year. Early dry-season
burning promotes its growth, whereas late burning promotes the unpalatable Loudetia
acuminata (Ramsey & Rose-Innes, 1963).
Dry-matter and green-matter yields
Adegbola (1964) recorded 14 800 kg DM/ha per year at Agege (Lagos), Nigeria. In India 3
300 kg/ha fresh grass was obtained. Hendy (1975) obtained a production of 40 000 kg DM/ha
per year at the Livestock Research Station, Tanga, United Republic of Tanzania, from a
fertilizer application of 44 kg P2O5, 30 kg K2O and 50 kg N/ha per year. A selection of A.
gayanus, No. 621 from Shika, Nigeria, yielded 4 000 kg DM/ha at Quilichao, Colombia
without fertilizer nitrogen but with adequate phosphorus (CIAT, 1978).
Suitability for hay and silage
It has been conserved as silage and hay, but its low nutritive value (Ademosun, 1973)
does not justify the work involved (Miller, Rains & Thorpe, 1964).
Value as a standover or deferred feed
It is coarse and of low nutritive value after maturity, with only 1.5 percent crude
protein (Miller, Rains & Thorpe, 1964).
Toxicity
No toxicity has been reported by Everist (1974).
Seed yield
Haggar (1966) recorded 21-86 kg/ha. Caryopses constitute 10 percent of this figure. At
CIAT, Colombia, 34 kg/ha of pure live seed was harvested manually. Collection of shattered
seed from the ground increased yield and germination capacity, when not affected by the
weather (CIAT, 1978).
Cultivars
There are several different types of plants and four varieties:
- Var. bisquamulatus (Hochst.) Hack
common in the savannahs from Senegal to the Sudan, colonizing denuded and waste
land. It is very palatable to livestock.
in periodic swamps in the same region. Good for erosion control in damp places.
- Var. squamulatus (Hochst.) Stapf
occurring also in this area and extending to the United Republic of Tanzania,
Zimbabwe, Mozambique, Transvaal and Angola (Bowden, 1963b).
confined to Ghana (Rose-Innes, 1977). Bisquamulatus and squamulatus grow best on
well-drained sandy clays of medium to high fertility. Pasto Carimagua cv. 621 was to be
released by CIAT in 1980.
Diseases
It has no disease problems.
Main attributes
Its excellent growth and dry-matter production in acid infertile soils with minimum
inputs, exceptional tolerance to drought stress, burning, and high levels of aluminium
saturation; low P and N requirements; no known disease or major insect attacks; excellent
seed-producing ability; compatibility with legumes; adaptability to low-cost pasture
establishment systems, acceptable nutritional quality and high intake due to high
palatability; high animal production levels during the first year (CIAT, 1978). Its
adaptability to low-lying tropical areas which have low to moderate rainfall and its
ability not only to survive a long dry season of several months but also to remain green
for much of it and begin regrowth very early in the following rains to provide an early
bite (Bowden, 1963b).
Main deficiencies
As it approaches and reaches maturity, it coarsens and is also of low nutritional
value.
Optimum temperature for growth
The optimum temperature for flowering is 25°C (Tompsett, 1976).
Frost tolerance
It is probably not tolerant of frost.
Latitudinal limits
Probably about 20°N and S.
Response to light
It prefers to grow in full sunlight.
Ability to compete with weeds
It could suppress weeds by shading and root competition in dry areas.
Pests
It may be attacked by the Brazilian spittle bug (CIAT, 1978).
Palatability
It is palatable when young and cattle will eat it up to flowering. Palatability ranking
was A. gayanus > Panicum coloratum > P. maximum > Pennisetum purpureum (Bowden,
1963b).
Response to photoperiod
It is a short-day plant with a critical day length for flowering between 12 and 14
hours. Flowering increased as day length shortened from 12 to eight hours (Tompsett,
1976).
Chemical analysis and digestibility
Göhl (1975) lists its feeding analysis in Table 15.2, to which Boudet's (1970) figures
are added. Crude protein content in all categories of leaf and stem rose to a maximum at
ear emergence. Maximum yields of digestible nutrients can be obtained by cutting at that
time (Haggar & Ahmed, 1971). A. gayanus selection 621 gave low digestibility but high
nitrogen levels in Colombia (CIAT, 1978).
Natural habitat
Open woodland and savannah.
Tolerance to flooding
Rains (1963) lists A. gayanus var. gayanus among grasses growing in seasonally flooded
places.
Fertilizer requirements
A. gayanus performs very well without fertilizer nitrogen or phosphorus (CIAT, 1978)
and thus is a valuable grass for low-input pasture production. Haggar (1975) found the
highest return of dry matter per unit of fertilizer (14.4 kg DM/kg N) was from only 28 kg
N/ha and there was only a modest increase in crude protein up to 10.5 percent of the dry
matter with increasing nitrogen. However, Haggar (1975) obtained almost linear increases
in dry- matter production with increasing amounts of sulphate of ammonia up to 112 kg
N/ha, but from 112 kg to 896 kg N/ha yields were curvilinear with maximum yield at 500
kg/ha. Falade (1975) determined the optimum phosphorus content of the dry matter for
growth was 0.19 percent in a sandy loam soil at Ibadan, Nigeria when fully fertilized.
Andrew and Robins (1971) obtained a critical percentage of 0.185 in Queensland. Some basic
potassium may be required. It tolerates high aluminium (Spain, 1979). On the Quilichao
ultisol in Colombia, A. gayanus gave maximum yield in the establishment year without
fertilizer, and on the Carimagua oxisol the maximum yield was obtained with 50 kg P2O5/ha.
Phosphorus fixation in the Carimagua oxisol is about half that of the Quilichao ultisol
(CIAT, 1978).
Compatibility with other grasses and
legumes
It combines naturally with Stylosanthes fruticosa in the Sudan and the United Republic
of Tanzania and with Stylosanthes spp. and Desmodium ovalifolium and other legumes in
Colombia (CIAT, 1978).
Genetics and reproduction
2n=40 (20, 35, 40, 42, 43, 44; Fedorov, 1974).
Seed production and harvesting
Generally it is a good seed producer. Manual harvest produces more than 100 percent
more than mechanical methods. In India, Mishra and Chatterjee (1968) obtained the highest
yield by cutting twice a year (in mid-January and early July) and fertilizing with 38.9 kg
N/ha plus 22 2 P2O5/ha. It maintained its seed yield with a third cut late in August.
Economics
A. gayanus (gamba grass) is a dominant constituent of large areas of natural and sown
grasslands in Nigeria and other savannah areas of tropical Africa. It especially suits
low-lying tropical areas which have moderate to low rainfall and a long dry season. When
incorporated into a rotation it has been found to be a fertility builder. The stems are
used for weaving grass mats and for thatching (Bowden, 1963b). It is a promising grass in
northern Australia.
Animal production
In Nigeria, natural grassland containing 60 percent of A. gayanus resulted in a weight
gain of 0.31 kg per day when grazed by N'Dama and Keteku cattle, but when consumed as
silage the weight gain was 0.11 kg/ day (Adegbola, Onayinka & Eweje, 1968).
Further reading
Bowden, 1963b; CIAT, 1978.
Dormancy
Germination improves for a time with storage.
Value for erosion control
It has been used in Kano, Nigeria for reclaiming badly overgrazed and eroded land
(Bowden, 1963b). |
