Brachiaria humidicola (PROSEA)
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Introduction |
Brachiaria humidicola (Rendle) Schweick.
- Protologue: Kew Bulletin 1936: 297 (1936).
- Family: Gramineae
- Chromosome number: 2n= 72
Synonyms
Panicum humidicola Rendle (1899).
Vernacular names
- Koronivia grass (En)
- Thailand: ya humidicola.
Origin and geographic distribution
The origin and natural distribution of B. humidicola extends throughout eastern and southern Africa. During the past 2-3 decades, it has been introduced to other tropical regions and has become a fairly widespread species in South-East Asia and the Pacific region.
Uses
Koronivia grass is mainly used as a forage in permanent pastures that are grazed, and for erosion control. It has also proved to be useful as grazed ground cover in tree plantations.
Properties
Koronivia grass has a reputation as a palatable forage with very low N concentrations, even during the growing season (0.6-1.0%), which can severely limit forage intake by ruminants. In vitro DM digestibility values range from 50-70%. The grass tolerates shade and poor drainage and is an effective seed producer. There are 200-260 seeds/g.
Botany
A prostrate, strongly stoloniferous and rhizomatous perennial, forming a dense ground cover. Stolons slender but strong and of reddish colour; flowering stems ascend up to 100 cm. Leaf linear to narrowly lanceolate, 4-30 cm × 3-10 mm, glabrous. Inflorescence consisting of 2-5 racemes on an axis 2-13 cm long; racemes 2-7 cm long, bearing the spikelets in two rows; spikelets broadly elliptic, 4-6 mm long, slightly pubescent; lower glume 75-100% of spikelet length; 11-nerved; upper glume 5-9-nerved; lower lemma 5-nerved; upper lemma slightly papillose.
Koronivia grass can easily be confused with B. dictyoneura (Fig. & De Not.) Stapf. The main difference is that koronivia grass is very strongly stoloniferous while B. dictyoneura is distinctly tufted and considerably less stoloniferous. There are several cultivars throughout the tropics; however, they probably represent the same genotype. Officially released cultivars are "Tully" in Australia and "INIAP-701" in Ecuador. The reproduction in cultivars is apomictic.
Ecology
Koronivia grass is well adapted to the humid tropics but also thrives under sub-humid tropical conditions where it withstands 3-4 dry months. It grows well on a range of soils, including moist, poorly drained sites. It is particularly well adapted to acid, highly Al-saturated soils of low fertility.
Agronomy
Koronivia grass can be propagated and established by seed at a rate of 2-8 kg/ha depending on seed quality, or vegetatively by rooting stolon cuttings that are spread and disked in, or planted by hand, at 1 m × 1 m distances or less. The latter method is particularly convenient in smallholder systems.
Under favourable conditions, koronivia grass can grow very quickly and form a dense ground cover ready for grazing 3-5 months after sowing. Because of its growth habit and highly competitive vigour, the growth of weeds is easily suppressed, but associations with legumes are difficult to maintain.
In contrast to lower altitudes, koronivia grass grown at higher altitudes has the potential to flower profusely and to produce seed yields of up to 150 kg/ha during the first year. Once the pasture is fully established, flowering and seed production are scarce.
Because of its strongly stoloniferous growth habit, koronivia grass can withstand very heavy grazing. Overstocking, however, will result in very low animal growth rates. Prostrate-stoloniferous legumes such as Arachis pintoi Krap. & Greg., nom. nud. (Pinto peanut), Desmodium heterophyllum (Willd.) DC. (hetero), and D. heterocarpon (L.) DC. ssp. ovalifolium (Prain) Ohashi have the potential to persist readily in associations with koronivia grass. However, when all soil nutrient deficiencies have been corrected, Centrosema pubescens Benth. and Pueraria phaseoloides (Roxb.) Benth. have also persisted with it. Although its requirements for soil fertility are low, it responds to fertilization.
As with most other Brachiaria species, the productivity of koronivia grass can be affected by spittlebug ( Aeneolamia spp., Deois spp., and Zulia spp. in the Cercopidae family). Unlike most other Brachiaria species, however, it recovers quickly from attacks by this insect pest. Rust ( Uromyces setaria-italicae ) has recently been identified as a potential major disease in tropical America.
Koronivia grass is regarded as a high-yielding grass. Depending on climate and soil fertility, DM production ranges from 7-33 t/ha per year. Because of its high carrying capacity, liveweight gain per ha can be high, but with rather low growth rates (150-500 g/steer per day). Although the grass is usually consumed fresh by grazing animals, hay making is occasionally practised in sub-humid environments in Brazil and Venezuela.
Genetic resources and breeding
There is no variation in cultivars of koronivia grass as their reproduction is apomictic, resulting in progenies being clones of the mother plant. The major germplasm banks of tropical forage grasses at CIAT (Colombia) and ATFGRC (CSIRO, Australia) hold a range of quite variable B. humidicola accessions. At present, there are no B. humidicola breeding programmes. Research activities to improve the species are limited to evaluation of the available genepool.
Prospects
Because of its aggressive, weed-suppressing growth, tolerance of overgrazing, adaptation to poorly drained sites, and low requirements regarding soil fertility, the present Koronivia grass cultivars will continue to play an important role in tropical pasture development. Their importance will only decline when new cultivars or other species become available which combine the above-mentioned features with better forage quality.
Literature
- Bogdan, A.V., 1977. Tropical pasture and fodder plants. Longman, London. pp. 57-58.
- Centro Internacional de Agricultura Tropical, 1983-1990. Annual reports, Tropical Pastures Program. CIAT, Cali, Colombia.
- Oram, R.N., 1990. Register of Australian herbage plant cultivars. CSIRO, Australia. pp. 91-92.
- Skerman, P.J. & Riveros, F., 1990. Tropical grasses. FAO, Rome. pp. 245-248.
- 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
