Brachiaria ruziziensis
Germain and Everard

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Graminae

Synonyms

Brachiaria eminii Mez.

Common names

Kennedy ruzi grass (Australia), Congo signal grass (Africa), prostrate signal grass (Kenya).

Description

A spreading perennial with short rhizomes, similar in habit to Para grass. The inflorescence consists of dense and spikelike racemes. The spikelets are all sessile and close together, the rachis of the racemes winged, broad and over 3 mm wide. The spikelets are hairy and the lower glume under half the length of the spikelet (Harker & Napper, 1960). It has softer leaves than B. brizantha.

Distribution

Lake Edward and Lake Kivu districts, Rwanda, Burundi, and the Ruzizi plains in Zaire, now widely distributed in the tropics.

Season of growth

Summer.

Altitude range

1 000-2 000 m in Kenya, up to 1 200 m in Panama (Rattray, 1973).

Rainfall requirements

It requires a reasonably high rainfall, but can endure hot dry spells. A rainfall of 1 000 mm or more is best.

Drought tolerance

It has good drought tolerance.

Soil requirements

It requires a soil of high fertility, such as latosols carrying mesophyll rain forest. It will tolerate acid soils. It needs good drainage.

Ability to spread naturally

It spreads well from rhizomes.

Land preparation for establishment

A well-prepared seed-bed is recommended, but light disc-harrowing gives good results.

Sowing methods

Drill the seed into a well-prepared seed-bed. In Zaire it has been sown in rows 60 cm apart, or broadcast over the land after scarification of the soil with a disc harrow or brushcutter, without burning the native pastures, and grazed as soon as it is ready (Risopoulos, 1966).

Sowing depth and cover

Surface sow in moist soil, and sow no deeper than 2 cm in dry soil (Bogdan, 1964). In Zaire it is recommended to sow at a depth of 1-2 cm. Under humid conditions seeds lose their vitality after one year (Risopoulos, 1966).

Sowing time and rate

In Zaire the seed rate recommended is 30 kg/ha.

Number of seeds per kg.

About 250 000.

Seedling vigour

Excellent (Davidson, 1966).

Vigour of growth and growth rhythm

It gives good early wet season growth for eight weeks after the opening rains (Falvey, 1976) and it seeds heavily in April at South Johnstone, north Queensland (lat. 1736'S).

Response to defoliation

It forms a dense mat under grazing which withstands grazing well (Davidson, 1966). The yields of dry matter did not vary very significantly in Sri Lanka with monthly cutting at 2.5 cm or 7.6 cm but bimonthly cuts yielded a little higher (Appadurai & Goonawardene, 1973).

Grazing management

In combination with Stylosanthes humilis in northern Australia it must be grazed heavily to maintain this legume in the sward (Falvey, 1976).

Response to fire

Selection 6019 at CIAT, Colombia, does not tolerate fire (CIAT, 1978).

Suitability for hay and silage

It made very good silage with Stylosanthes guianensis in Zaire with 1 percent molasses and without additive (Risopoulos, 1966) and made good hay in Zambia (van Rensburg, 1969).

Toxicity

No toxicity has been recorded by Everist (1974).

Seed yield

A seed yield of 125 kg/ha has been recorded in Queensland and 200 kg/ha in Zaire (Risopoulos, 1966).

Cultivars

'Kennedy', described above, is the only present cultivar. Selection 6019 has been tested at CIAT, Colombia.

Diseases

It is comparatively free from diseases.

Main attributes

Its fast growth early in the wet season, its compatibility with Stylosanthes humilis and S. hamata, its good seed production and ease of establishment.

Main deficiencies

Its winter growth is slow. It needs well-drained fertile soils.

Optimum temperature for growth

33C day, 28C night (Dienum & Dirven, 1972).0

Minimum temperature for growth

Low yields resulted from a 24/19C regime. Ludlow (1976) found this species, of several tropical grasses, the most affected by low temperatures.

Frost tolerance

It is killed by heavy frosts, and spring regrowth is very slow after light frosts.

Response to light

Yields increase with increasing light intensity (Dienum & Dirven, 1972).

Ability to compete with weeds

It successfully suppresses weeds.

Maximum germination and quality required for sale

The seed is germinated at 20-35C after treatment with sulphuric acid for ten minutes. Fifteen percent germinable seed and 40 percent purity in Queensland.

Pests

There are few pests.

Palatability

It is very palatable. At the Cerrado Centre, Brazil, it was preferentially grazed ahead of Stylosanthes guianensis during the rainy season.

Chemical analysis and digestibility

High temperatures have an adverse effect on digestibility (Dienum & Dirven, 1972). Digestibility decreased in 18-day material from 78.4 percent at day/night temperatures of 24/18C to 72.7 percent at 29/30C and 69.5 percent at 34/30C (Dirven, 1973). Feeding value declined when it seeded heavily at South Johnstone, Queensland, in April (Mellor, Hibberd & Grof, 1973a). Scaut (1959) in Zaire found fresh grass to contain 13.9 percent crude protein, 27.2 percent crude fibre, 9.0 percent ash, 2.3 percent ether extract and 47.6 percent nitrogen-free extract in the dry matter.

Natural habitat

A pioneer species of cleared rain forest in Africa.

Tolerance to flooding

It does not tolerate flooding.

Fertilizer requirements

It needs high phosphorus in the early growth on a wide range of soils. It responds well to nitrogen, either inorganic or from legumes, but its nitrogen requirement exceeds that of Guinea grass, which makes the latter more attractive (Mellor, Hibberd & Grof, 1973b). Risopoulos (1966) recorded an increased yield of 10 739 kg/ha from nitrogen application in Zaire.

Compatibility with other grasses and legumes

Ruzi grass combines well with legumes such as Centrosema pubescens or Pueraria phaseoloides if the mixture is leniently grazed. In Zaire it has combined well with Setaria sphacelata and Stylosanthes guianensis. In northern Australia Stylosanthes humilis and S. hamata can be introduced by cultivating the grass and oversowing the legumes (Falvey, 1979).

Genetics and reproduction

It appears to be apomictic.

Seed production and harvesting

It seeds heavily at Gandijika, Zaire (lat. 645'S with four months dry season) (Risopoulos, 1966). Seed can be harvested in May in Queensland, either by hand or with a tractor-mounted buffer type seed harvester but yields are lower by this method (Davidson, 1966).

Economics

An important grazing species in the wetter tropics.

Animal production

Brahman steers grazing Kennedy ruzi grass at Utchee Creek, north Queensland, gave a poor winter performance on grass in association with legumes compared with the performance on Guinea grass, but nearly equalled Guinea when 27 kg N/ha was applied. Ruzi grass/legume pastures produced 1 157 kg/ha live- weight gain, while ruzi grass plus 200 kg N/ha per year gave 1 513 kg/ha live-weight gain (Mellor, Hibberd & Grof, 1973a).

Links for the genus:

Further reading

Davidson, 1966; Dienum & Dirven, 1972; Mellor, Hibberd & Grof, 1973.J

Dormancy

Fresh seed shows post-harvest dormancy and delayed germination. Fresh seed gave 20 percent germination in Queensland, and after 12 months' storage this increased to 40 percent (Davidson, 1966). Dormancy can also be broken by treating the seed with concentrated sulphuric acid for 15 minutes (Barnard, 1969) or mechanical scarification (Jones, 1973).

Value for erosion control

It is useful for erosion control in areas where it grows well.

Green-matter and dry-matter yields

In Tanzania, ruzi grass yielded 21 159 kg DM/ ha (Naveh & Anderson, 1967). At South Johnstone, north Queensland it yielded 19 500 kg DM/ha under a six-week cutting interval and an input of 220 kg N/ha/year (Grof & Harding, 1970). In Sri Lanka yields of 16 807, 22 031 and 25 585 kg DM/ha per year with nitrogen applications of 112, 224 and 366 kg N/ha (Appadurai, 1975). In French Guyana the yield was 20 574 kg DM/ha and 1 180 kg/ha crude protein (Borget, 1966) and in Zaire yields of 31 352 kg and 21 468 kg green matter per hectare per year were obtained in successive years, 1958-59, with 100 kg nitrogen and 100 kg superphosphate per hectare per year (Risopoulos, 1966). At Gualaca, Panama, it produced 11 000 kg DM/ha without fertilizer and 27 000 kg DM/ha when fertilized with 600 kg N/ha per year in a rainfall area of 3 997 mm per year.