Brachiaria dictyoneura (PROSEA)
 |
Introduction |
Brachiaria dictyoneura (Fig. & De Not.) Stapf
- Protologue: Flora of Trop. Africa 9: 512 (1919).
- Family: Gramineae
- Chromosome number: 2n= 42
Synonyms
Panicum dictyoneurum Fig. & De Not. (1854), Brachiaria obvoluta Stapf (1919), B. keniensis Henr. (1940).
Vernacular names
- Thailand: ya signal luey.
Origin and geographic distribution
B. dictyoneura has its origin and natural distribution in eastern and southern Africa. It is increasingly being introduced to South-East Asia and the Pacific region and is spreading quite quickly in tropical America.
Uses
B. dictyoneura is used as a forage in permanent pastures that are grazed. It has potential for erosion control and also as ground cover in tree plantations.
Properties
The nutritive value of B. dictyoneura is regarded as moderate, yet higher than that of koronivia grass ( B. humidicola (Rendle) Schweick.). Nitrogen concentrations range mostly between 1-2% but can be as low as 0.5% during the dry season. The range for in vitro DM digestibility is 55-70%. The grass has a high seed-production potential; there are about 170 seeds/g.
Botany
A densely tufted, semi-erect, stoloniferous perennial with short rhizomes and with stems 40-120 cm high; stolons slender but strong and of reddish colour. Leaf linear to lanceolate, 4-40 cm × 3-18 mm, glabrous and with strongly denticulate margins. Inflorescence consisting of 3-8 racemes on an axis 5-25 cm long; racemes 1-8 cm long, bearing spikelets in two rows; spikelets elliptic, 4-7 mm long, pubescent; lower glume 75-100% of spikelet length, 11-nerved; upper glume 7-9-nerved; lower lemma 5-nerved; upper lemma slightly papillose.
Flowering seems to be long-day induced, and seed-setting improves at higher latitudes. In cultivars, reproduction is apomictic.
B. dictyoneura can easily be confused with B. humidicola (koronivia grass). The latter is, however, much more stoloniferous than B. dictyoneura. Further important differences, at least regarding the cultivars or commercial lines, are that B. dictyoneura has a noticeable, undulating protuberance along the leaf-collar (outer surface of the junction of leaf-sheath and blade), and that the raceme-rachis of B. dictyoneura is remarkably long-ciliate at the margins. The only cultivar released so far is "Llanero" in Colombia.
Ecology
B. dictyoneura is well adapted to the humid and sub-humid tropics where it withstands dry periods of up to 4-5 months. It grows well on a wide range of soils, provided they are well drained, including acid and highly Al-saturated soils of low fertility.
Agronomy
B. dictyoneura is preferably propagated by seed, but can be propagated vegetatively by rooted stem segments or stolons. Recommended seeding rate is 2-12 kg/ha, depending on seed quality. Germination of fresh seed is very poor because of dormancy, mainly physiological. Scarification with sulphuric acid improves germination only slightly; therefore, it is recommended to use seed that is 6-8 months old.
Its slow intial growth and weakly stoloniferous growth habit enable association with a range of legumes of varying growth habits, such as Desmodium heterocarpon (L.) DC. ssp. ovalifolium (Prain) Ohashi (prostrate-stoloniferous), Centrosema pubescens Benth. or Pueraria phaseoloides (Roxb.) Benth. (trailing-climbing), Stylosanthes guianensis (Aublet) Swartz (semi-erect herb/subshrub), and Leucaena leucocephala (Lamk) de Wit (shrub/tree).
Although its soil-fertility requirements are low, B. dictyoneura responds well to fertilization, particularly with N. B. dictyoneura should be leniently grazed until it is fully established. Then, using continuous or rotational grazing, stocking rates can be relatively high (2-4 steers/ha), with seasonal adjustments as necessary. The grass should be grazed down to 15-20 cm height.
Like most other species of Brachiaria, B. dictyoneura is affected by spittlebug (species of the genera Aeneolamia, Deois, and Zulia in the Cercopidae family) in tropical America. However, unlike signal grass ( B. decumbens Stapf), it recovers quickly.
B. dictyoneura is usually harvested as fresh material by grazing animals. Depending on growth conditions, including the severity of the dry season, the grass produces DM yields ranging from 4-11 t/ha per year on acid, low-fertility soils. Animal production on a hectare basis varies accordingly. Daily liveweight gains of 250-500 g/steer can be expected.
Genetic resources and breeding
There is no variation within "Llanero"; as its reproduction is apomictic, the progenies are essentially clones of the mother plant. The species is not very well represented in the major germplasm banks of tropical forage grasses at ATFGRC (CSIRO, Australia) and CIAT (Colombia), and only a few but distinct accessions are so far available. There are no breeding programmes involving B. dictyoneura .
Prospects
Compared with other Brachiaria species adapted to acid, low-fertility soils, B. dictyoneura offers the advantage of being less affected by spittlebug than signal grass and the advantage of better forage quality and compatibility with legumes than koronivia grass. For these reasons, it has excellent potential for pasture development in acid-soil regions.
Literature
- Centro Internacional de Agricultura Tropical, 1983-1990. Annual reports. Tropical Pastures Program. CIAT, Cali, Colombia.
- Instituto Colombiano Agropecuario, 1987. Pasto "Llanero". ICA, Bogotá, Colombia. Boletín Técnico No 151. 12 pp.
- Keller-Grein, G. (Editor), 1990. Red Internacional de Evaluación de Pastos Tropicales RIEPT-Amazonia. I Reunión-Lima, Perú, 6-9 Noviembre 1990. Documento de Trabajo No 75. Centro Internacional de Agricultura Tropical, Cali, Colombia. 2 Vols. 1119 pp.
Authors
R. Schultze-Kraft
