Cynodon dactylon (L.) Pers.

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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

  • '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.
  • 'Coastal Bermuda Grass' 
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.
  • 'Tiff Bermuda' 
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.
  • 'St Lucia Bermuda Grass' 
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).
  • 'Alicia' 
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).
  • 'Callie' 
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).
  • 'Oklan' 
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'.
  • 'Suwannee Bermuda' 
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.
  • 'Coast Cross-1' 
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.
  • 'Midland' 
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.
  • 'Hardie' 
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).
  • 'Greenfield' 
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:
  • dactylon (4X) 
Bermuda grass. A cosmopolitan weed, turf grass and forage grass.
  • aridus (2X) 
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.
  • afghanicus (2X, 4X) 
Afghanistan.
  • coursii (4X) 
Madagascar.
  • elegans (4X) 
Africa south of 12°S latitude.
  • polevansii (4X) 
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.