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Graminae
Common names
Couch grass, green couch (Australia), Bermuda grass (United
States), kabuta (Fiji), dhoub grass (Bangladesh), Bahama grass, quick grass
(South Africa), chepica brave, came de niño, pate de perdiz, gramilla
blanca (Peru), hierba-fina (Cuba), griming, tigriston (Suriname).
Description
A variable perennial, creeping by means of stolons and rhizomes,
eight to 40 culms, (rarely) to 90 cm high: leaves hairy or glabrous, three
to seven spikes (rarely two), usually 3-6 cm long and in one whorl, or
in robust forms up to ten spikes, sometimes in two whorls: spikelets 2-3
mm long, rachilla often bearing a reduced floret (Chippendall, 1955). It
differs from Digitaria scalarum (African couch) in the vegetative stage
in that there is no obvious membranous ligule where the leaf-blade joins
the sheath (Ivens, 1967).
Distribution
Wheeler (1950) says the best evidence is that is originated
in Asia, particularly India, and has now become pan-tropical.
Altitude range
Sea-level to 2 300 m.
Rainfall requirements
It usually occurs over a range of 625-1 750 mm of annual rainfall.
Drought tolerance
Good. The rhizomes survive drought well. Coastal Bermuda grass
has proved very drought resistant in Georgia, United States.
Soil requirements
There are varieties adapted for a wide range of soils. Coastal
Bermuda prefers well- drained, fertile soils, especially heavier clay and
silt soils not subject to flooding, well supplied with lime and high-nitrogen
mixed fertilizers. Lawn couch grass is most frequently grown for sale on
sandy loams easy to dig and rebuild.
Ability to spread naturally
C. dactylon spreads quickly by rhizomes and stolons, and less
obviously by seed.
Land preparation for establishment
If planted by turf, rough ploughing will be sufficient, but
if for a lawn grass sown from seed, a very well-prepared, fine, weed-free
seed-bed is needed.
Sowing methods
It is usually sown as turfs or as seed for lawns. 'Coastal
Bermuda Grass' is sown by seed or, more often, with sprigs, as it produces
few viable seeds.
Sowing depth and cover
It is surface sown and rolled in. Sowing time and rate. Sow
in summer at 9-11 kg/ha.
Number of seeds per kg.
4 489 000.
Seed treatment before
planting
Treat with lindane dust if seed-harvesting ants are about.
Tolerance to herbicides
Dalapon at 6-12 kg/ha applied to young growth can give a high
degree of control. Repeated cultivations will kill the plant, but repeated
spraying with herbicides are effective. Spray young, vigorously growing
plants with paraquat at 2.8 l/ha of a 200 g AI/I product (e.g. Gramoxone)
plus surfactant at 250 ml/200 l of water, using a minimum of 400 ml water
per hectare. TCA 2,2,-DPA and glyphosate (Round up) can also be used (Tilley,
1977).
Seedling vigour
Seedlings usually root down quickly.
Vigour of growth and growth
rhythm
It grows vigorously once established.
Response to defoliation
It stands close grazing probably better than any other grass.
Response to fire
It will stand severe fires due to the extensive rhizome development
in most varieties and cultivars.
Dry-matter and green-matter
yields
Coastal Bermuda grass receiving 550 kg/ha of complete 4-8-4
fertilizer plus 520 kg/ha of nitrate of soda produced 6 tonnes of air-dried
hay in four cuttings in Georgia. Strickland (1976-77) recorded a range
of dry-matter yields of 1 000-3 000 kg/ha per month in summer and 100-1
200 kg in winter at Samford, Queensland, from 20 accessions of Cynodon
dactylon.
Suitability for hay and
silage
Coastal Bermuda grass gives excellent hay, very quickly cured,
and, if fertilized, of excellent nutritive value. It is frequently pelleted
in the United States. Harvesting at eight weeks increased dry matter but
reduced crude protein in comparison with a four-week cut (Utley et al.,
1978). It makes good silage, but not of the lactic acid type when ensiled
with 41 kg maize grain per tonne. The pH was 5.0, volatile acid content
was only 2-4 percent of the dry matter and it had the appearance of haylage
(Miller, Clifton & Cameron, 1963).
Value as a standover or
deferred feed
It will provide standover or deferred feed if closed for grazing.
Toxicity
Most of the Cynodon dactylon types are non-toxic but an occasional
case of HCN poisoning may occur. In the United States, frosted Bermuda
grass can cause photosensitization. Kidder, Beardsley and Erwin (1961)
and Ndyanabo (1974) recorded 1.10 percent total oxalic acid in the dry
matter but no toxicity.
Seed yield
Cv. Coastal Bermuda, 275-350 kg/ha.
Cultivars
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'Common Bermuda Grass', or C. dactylon var. dactylon
a tetraploid (2n=36) originating in the Near East and is
the common weed of arable land. It is excellent for erosion control and
gives valuable feed especially in winter, though limited in quantity.
bred by Dr Glen Burton of Tifton, Georgia, United States,
from a cross between C. dactylon var. dactylon and C. dactylon var. elegans.
It is outstanding for hay and pasture and has a wide soil range. It is
larger than 'Common Bermuda Grass' with longer internodes. The leaves have
a characteristic light green colour. It is almost seedless, but seed can
be obtained. It is larger and more erect in habit than 'Tift', and its
lighter green and more flexible leaves droop more than those of 'Tift'.
More frost resistant than 'Common Bermuda'. It responds remarkably to nitrogen
fertilizer. It is best planted as pieces of sod. It produced a yearly average
of 130 kg/ha more live-weight gain than common couch.
found in a cotton field near Tifton, Georgia, United States.
It has long decumbens stems, few seed-heads and an abundance of large stolons
and rhizomes. It is superior to 'Common Bermuda' or couch grass for both
hay and pasture.
establishes and spreads by surface runners. It has no rhizomes.
It is adapted to the muck and sandy muck soils underlain by lime on the
lower east coast of Florida, United States (Wheeler, 1950).
does not produce high-quality forage and is not very winter
hardy. It spreads rapidly, established by cuttings or rhizomes. Forage
digestibility is lower than for 'Coastal Bermuda' (Bates, 1978).
adapted to the area south of the line from North Carolina
to Texas, United States. It is not winter hardy. It spreads and establishes
very fast, gives hay yields 10-15 percent higher than 'Coastal' and is
more digestible (Bates, 1978).
not as winter hardy as 'Hardie' or 'Midland'. Propagated
by stolons. Has high digestibility and good forage quality. Starts growth
later in spring than 'Midland'.
developed at the Coastal Plains Experiment Station, Tifton,
Georgia. Is better adapted to soils of low fertility than 'Coastal' and
is used in poor soils in Florida. It will not withstand close grazing.
adapted to the southern United States, not as winter hardy
as 'Coastal' or 'Oklan' and has lower forage production. A good hay type
with high digestibility and better animal performance than other varieties.
Starts late in spring.
the standard cultivar for Oklahoma, United States. The most
winter hardy of the improved, upright, high-producing cultivars. Adapted
to shallow, drought-prone soils. Starts off early in spring but is slow
spreading.
more winter hardy than 'Coastal' or 'Oklan'. Grows best
on deep, fertile soils, has high digestibility and gives good daily gains.
Suitable for hay. Starts growth early in spring. Produces a lot of forage
(Bates, 1978).
best for erosion control with heavy growth of rhizomes and
stolons, fast spreading and grows well on thin, eroded soils. Winter hardy
and produces early spring growth (Bates, 1978).
Diseases
C. dactylon is attacked by Helminthosporium leaf diseases in
some areas.
Main attributes
Cynodon dactylon has wide adaptability to soils and climate.
It is palatable, nutritious, and stabilizes soil against erosion, stands
heavy grazing and makes useful hay and silage.
Main deficiencies
It can become a weed in cultivation and it does not provide
much bulk unless well fertilized.
Optimum temperature for
growth
35°C (Evans, Wardlaw & Williams, 1964), 37.5°C
(Loworn, 1945).
Minimum temperature for
growth
Grows very slowly at 15°C (Evans, Wardlaw & Williams,
1964). Day temperatures must exceed 10°C. The minimum temperature regime
for growth consists of an eight- hour day at 15°C and a 16-hour night
at 5°C (Youngner, 1959).
Frost tolerance
It frosts but recovers.
Latitudinal limits
30°N and 31.4° + 7.5° S (Russell & Webb, 1976).
Response to light
It usually dies out under medium to dense shade.
Ability to compete with
weeds
It suppresses weeds well if kept mown or grazed closely and
fertilized.
Maximum germination and
quality required for sale
60 percent germinable seed, 97 percent purity (Queensland).
Germinate at 20-30°C, moisten with KNO3 solution.
Pests
Root knot nematodes attack common couch grass in sandy soils.
Coastal Bermuda grass is more resistant to attack.
Palatability
It is very palatable if kept short in growth and fertilized.
Response to photoperiod
It is indifferent to day length for flowering (Evans, Wardlaw
& Williams, 1964).
Chemical analysis and
digestibility
Karue (1974) recorded the chemical composition as percent of
the dry matter of grass receiving no special treatment in Kenya in Table
15.20. Göhl (1975) lists 11 analyses. Crude protein varies from 8.3
percent in mature to 14.0 percent in young grass. Burton, in Georgia, United
States, has been able to reach 22 percent in nitrogen-fertilized grass
for pelleting for poultry food.
Natural habitat
Grassland, lawns and pastures and as a weed in cultivation.
Tolerance to flooding
In Bangladesh couch grass survives the annual flooding of the
Ganges- Brahmaputra rivers to a depth of 6 m or more for several weeks.
It is then oversown with Lathyrus sativus (Khesari) and used for dairy
cattle grazing.
Fertilizer requirements
A good basic fertilizer with additional levels of nitrogen
according to purpose. With 'Coastal Bermuda Grass', the efficiency of nitrogen
utilization begins to decline with 220 kg/ha for hay production and 450
kg/ha for protein production. Application of farmyard manure and sulphate
of ammonia to mixed pasture at Kongwa, Tanzania, caused an invasion by
Cynodon dactylon and suppression of Chloris gayana and Cenchrus ciliaris
(Wigg, Owen & Mukurasi, 1973). The average rainfall at Kongwa is 562
mm per year. In southern Texas, United States, C. dactylon fixed 30 kg
N/ha in 100 days (Wright, Weaver & Holt, 1976).
Compatibility with other
grasses and legumes
'Coastal Bermuda' combines with lespedeza and white clover
well. For north-east Thailand it is combined with Stylosanthes humilis
(McLeod, 1972).
Genetics and reproduction
2n=18, 27, 30, 36, 40 (Fedorov, 1974). Harlan, de Wit and Rawal
(1970) recognize six varieties:
Bermuda grass. A cosmopolitan weed, turf grass and forage
grass.
giant Bermuda grass. Southern India to Israel and the Sinai,
and sparingly southward in dry areas to the Karoo of South Africa. Introduced
to Hawaii and Arizona.
Afghanistan.
Madagascar.
Africa south of 12°S latitude.
near Barkerspan, South Africa.
Seed production and harvesting
In the United States two seed harvests of 'Coastal Bermuda'
are madeJuly and November. It is mowed into windrows, picked up and
threshed by combines and subsequently cleared.
Economics
A valuable lawn grass of wide adaptability. It produces excellent
forage when adequately fertilized.
Animal production
In Zimbabwe, C. dactylon fertilized with 270 kg nitrogen and
38 kg phosphorus per hectare gave a live-weight gain of 480 kg/ha from
grazing 12.4 heifers per hectare (Rodel, 1970). Live-weight gains on 'Coastal
Bermuda Grass' in Georgia over the period 1950-52, with varying rates of
nitrogen, are shown in Table 15.21 (Johnson, McGill & Gurley, 1960).
Further reading
Johnson, McGill & Gurley, 1960.
Dormancy
No seed dormancy has been reported.
Value for erosion control
It has saved untold areas of soil from erosion by wind and
water. It is a hardy pioneer which colonizes bare ground and holds and
accumulates soil. It helps to bind the edges of roads and provides excellent
grazing for village geese, ducks, goats, cattle and buffaloes if not trampled
too much by these latter heavy beasts.
Tolerance to salinity
Common couch has good tolerance to salinity, but makes only
slow growth. It is able to shunt its photosynthate from the tops to the
roots to enable it to survive under saline conditions (Youngner & Lunt,
1967). It gave maximum yields up to ECe 7 mmhos/cm, 50 percent at 15 mmhos/cm
and nil at 22.5 mmhos/cm (Mass & Hoffman, 1976).
Management
Graze closely to keep the feeding value high, and fertilize
with nitrogen. Renovate by ploughing or discing when sod-bound.
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