Brachiaria brizantha (PROSEA)
Brachiaria brizantha (A. Rich.) Stapf
- Protologue: Flora of Trop. Africa 9: 531 (1919).
- Family: Gramineae
- Chromosome number: 2n= 36, 54
Panicum brizanthum Hochst. ex A. Rich. (1851).
- Palisade grass, palisade signal grass (En)
- Thailand: ya siknaentontang.
Origin and geographic distribution
The origin of B. brizantha is Africa where the species has a very wide distribution throughout the wetter tropics. In recent decades, experimental lines and cultivars have been introduced to other parts of the world, including tropical Asia and the Pacific region.
The main use of palisade grass is as forage in permanent pastures for grazing or for cut-and-carry systems. It has also proved useful as grazed ground cover in tree plantations.
Palisade grass provides a more palatable forage than signal grass ( B. decumbens Stapf) but of similar N concentration (2.5%) and in vitro DM digestibility (75%) in 2-week-old regrowth, falling to 1.0% N and 55% digestibility in 12-week-old regrowth. Like signal grass, B. brizantha can cause photosensitization in sheep and goats, but in Brazil, where the grass is widely used in pastures, no photosensitization effects on cattle have been observed. There are 130-180 seeds/g.
A tufted, prostrate or semi-erect to erect perennial with short rhizomes and stems 30-200 cm tall. Leaf linear to broadly linear, 10-100 cm × 3-20 mm, glabrous or hairy. Inflorescence consisting of 2-16 relatively long racemes (4-20 cm), with spikelets generally in one row; rachis 1 mm wide, usually purple; spikelets elliptic, 4-6 mm long, glabrous or with a few hairs at the tip; lower glume _ the spikelet length, clasping; upper glume cartilaginous, dully shining; upper lemma granulose.
B. brizantha intergrades with B. decumbens and the species are difficult to distinguish. It is, therefore, likely that in the literature the name B. brizantha sometimes actually refers to B. decumbens , and vice versa. The main difference between the cultivars or lines of B. brizantha and B. decumbens is in the growth habit: B. brizantha is tufted with a rather erect growth whereas B. decumbens is low-growing and forms a dense cover. Two cultivars have been released in South America: the best known and most widespread is "Marandú" (Brazil) whereas "La Libertad" is a recent Colombian release.
Like signal grass, palisade grass is well adapted to the humid and sub-humid tropics where it can withstand dry seasons of up to 5 months. It grows well on a range of soils including sandy and acid soils, but it requires more fertile soil than signal grass. It does not tolerate poorly drained soils. Like signal grass, it tolerates light to moderate shade.
Although palisade grass can be established by spreading out stolon cuttings, it is mainly sown at rates of 1.5-12 kg/ha, depending on seed quality. Seed is broadcast or drilled 2-4 cm deep into conventionally prepared seed-bed. As germination of fresh palisade grass seed is affected by dormancy (hard-seededness), seed should be scarified with concentrated sulphuric acid, or seed that has been stored for 6-8 months should be used.
Palisade grass grows quickly, and 3-5 months after sowing, it can be ready for a first, light grazing. It responds well to fertilization with N, but also with P and K.
Although experience regarding persistence of legumes in association with palisade grass is limited, the less competitive growth habit of this grass, as compared with signal grass, suggests that it can be grown with a range of legumes representing distinct 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). Like signal grass, palisade grass pastures can be severely affected in their productivity and persistence by spittlebug (mainly the genera Aeneolamia, Deois and Zulia in the Cercopidae family). This pest, however, seems to be restricted to tropical America. The most wide-spread cultivar, "Marandú", is spittlebug-resistant.
Palisade grass can be continuously or rotationally grazed down to a height of 20-30 cm. It is harvested by grazing animals or is mown and fed fresh to animals in cut-and-carry systems. Dry matter yields of palisade grass vary, according to growth conditions, from 8-20 t/ha per year. At stocking rates of 1.5 steers/ha during the dry season and 2.5 steers/ha during the rainy season, annual liveweight gains can range between 400-500 kg/ha. It flowers and sets seed abundantly; a first seed crop is possible 6-8 months after sowing. Depending on environmental conditions, up to 3 seed crops per year can be obtained with a total seed yield of 100-500 kg/ha.
Genetic resources and breeding
Palisade grass, particularly the material from East Africa, is well represented in the major germplasm collections of tropical forage grasses such as CIAT (Colombia). At CIAT, parallel to evaluation and selection within the available large B. brizantha/B. decumbens gene pool, a breeding programme is in progress aiming at cultivars that combine spittlebug resistance, low soil-fertility requirements, and high nutritive value.
Palisade grass, mainly the spittlebug-resistant cultivar "Marandú", will continue to play an important role in the development of tropical pastures in regions where spittlebug is a major constraint until new Brachiaria cultivars with spittlebug resistance as well as lower soil-fertility requirements become available.
- Bogdan, A.V., 1977. Tropical pasture and fodder plants. Longman, London. p. 54.
- Cuesta, P.A. & Pérez, R.A., 1987. Pasto La Libertad. Instituto Colombiano Agropecuario (ICA), Bogotá, Colombia. Boletín Técnico No 150. 16 pp.
- Empresa Brasileira de Pesquisa Agropecuária, Centro Nacional de Pesquisa de Gado de Corte, 1984. Brachiaria brizantha cv. Marandú. EMBRAPA-CNPGC, Campo Grande-MS, Brazil. Documento No 21. 31 pp.
- Skerman, P.J. & Riveros, F., 1990. Tropical grasses. FAO, Rome. pp. 234-237.