Brachiaria ruziziensis (PROSEA)
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Introduction |
Brachiaria ruziziensis Germain & Evrard
- Protologue: Bull. Jard. Bot. Etat Brux. 23: 373 (1953).
- Family: Gramineae
- Chromosome number: 2n= 18, 36
Vernacular names
- Ruzi grass, Congo grass, Congo signal grass (En)
- Thailand: ya ruzi.
Origin and geographic distribution
Ruzi grass has its origin in the Ruzizi valley in eastern Zaire and Burundi. It is widely distributed on farms and experiment stations in most tropical countries including South-East Asia and the Pacific region.
Uses
Ruzi grass is used as a forage for direct grazing of permanent pastures, in the open or under coconuts, and for feeding tethered or stalled ruminants.
Properties
Ruzi grass is palatable and of excellent quality, with N concentrations ranging from 1.5-2.5% and in vitro DM digestibility from 50-75% (4-16 weeks old regrowth). It tolerates shade moderately, and drought fairly well. It has a high seed production potential. There are 230-250 seeds/g.
Botany
A tufted, creeping perennial, forming a dense and leafy cover. Stems leafy and hairy, arising from many-noded, creeping shoots and short rhizomes up to 1.5 m high when flowering. Leaves hairy, broad-lanceolate, 10-25 cm × 10-15 mm. Inflorescence consisting of 3-9 relatively long (4-10 cm) racemes, bearing spikelets in 1 or 2 rows on one side of a broad, flattened and winged rachis of generally purplish colour; spikelets hairy, 5 mm long; lower glume 3 mm long, 0.5-1 mm distant (= below) from rest of spikelet. It produces seed abundantly.
Brachiaria ruziziensis is very closely related to B. decumbens Stapf, but differs morphologically (in B. ruziziensis the rachis is subfoliaceous and 2-3.5 mm wide and the lower glume is at a considerable distance from rest of spikelet; in B. decumbens the rachis is flat, 1-1.7 mm wide and internode between lower and upper glume is shorter) and in reproduction (sexual in B. ruziziensis, apomictic in B. decumbens). The best known cultivar is "Kennedy", released in Australia.
Ecology
Ruzi grass is well adapted to the warm tropics with annual rainfall in excess of 1000 mm; it can withstand up to 5 dry months. It tolerates a range of soils but requires very fertile soil. It thrives best on well-drained sites.
Agronomy
Although it can also be propagated vegetatively by stem cuttings with rooting nodes, ruzi grass is easily established by seed at rates of 2.5-10 kg/ha, depending on seed quality. Seed should not be sown deeper than 1.5-2.5 cm. Germination of fresh seed is poor because of dormancy, but increases following storage or treatment with concentrated sulphuric acid.
Because of its high soil-fertility requirements, adequate N, either through a legume or fertilizer, P and K must be supplied in order to maintain high productivity of ruzi grass, particularly under cutting.
Ruzi grass can be sown with a range of legumes such as stylo ( Stylosanthes guianensis (Aublet) Swartz), greenleaf desmodium ( Desmodium intortum (Miller) Urban), centro ( Centrosema pubescens Benth.), and the shrub legume Leucaena leucocephala (Lamk) de Wit.
No diseases or pests of economic importance are known to affect ruzi grass in South-East Asia. In tropical America it can be severely damaged by spittlebug ( Aeneolamia spp., Deois spp., and Zulia spp. in the Cercopidae family). In Zaire the inflorescences are parasitized by the fungus Sphacelia sp.
Ruzi grass is harvested by grazing animals or cut for stall-feeding, and is also suitable for making hay. Depending on growth conditions (mainly soil fertility), annual DM yields of 10-20 t/ha can be expected from ruzi grass. Annual liveweight gains of beef cattle can be higher than 500 kg/ha, depending on soil N status.
Genetic resources and breeding
The gene pool of ruzi grass is limited to a few accessions held in the collections of ATFGRC (CSIRO, Australia) and CIAT (Colombia). Because of its sexual reproduction and a high degree of cross-pollination, these accessions are quite variable. There are no ruzi grass breeding programmes, but a tetraploid form of this species is used at CIAT as a source of sexuality in a breeding project involving the tetraploid, apomictic B. decumbens/B. brizantha complex.
Prospects
The main value of ruzi grass lies in its reasonably high nutritive value and high seed production potential, but it is markedly less productive than B. decumbens. Its importance will decrease rapidly as current Brachiaria selection programmes result in alternatives which combine the above mentioned attributes with adaptation to low-fertility soils.
Literature
- Bogdan, A.V., 1977. Tropical pasture and fodder plants. Longman, London. pp. 64-65.
- Reynolds, S.G., 1988. Pastures and cattle under coconuts. FAO plant production and protection paper 91. FAO, Rome. pp. 44-46.
- Skerman, P.J. & Riveros, F., 1990. Tropical grasses. FAO, Rome. pp. 255-259.
- Toutain, B., 1985. Graminées fourragères des genres Brachiaria et Urochloa pour le Pacifique [Grass forages of the genera Brachiaria and Urochloa for the Pacific]. Revue d'Elevage et de Médecine Vétérinaire de Nouvelle Calédonie 7: 47-56.
Authors
R. Schultze-Kraft & J.K. Teitzel
