Chloris gayana (PROSEA)
Chloris gayana Kunth
- Protologue: Révis. gramin. 1(18): 293 (1830).
- Family: Gramineae
- Chromosome number: 2n= 20 (diploid), 30, 40
Chloris abyssinica A. Richard (1851), C. glabrata Anderss. (1864).
- Rhodes grass (En, Am). Herbe de Rhode (Fr)
- Philippines: koro-korosan (Tagalog), banuko (Ilokano)
- Thailand: ya-rot
- Vietnam: tucgiéâ.
Origin and geographic distribution
Rhodes grass is native to East, Central, and the eastern part of West and southern Africa. It was first cultivated in South Africa, and at the beginning of the 20th Century it was introduced to a wide range of regions in Africa, South and Central America, the United States, Australia, South Asia, Japan, Italy and the southern part of the former Soviet Union. The grass is grown in Indonesia (Java, Irian Jaya, northern Sumatra), the Philippines and Thailand.
Rhodes grass is used in pastures for grazing, hay and silage making. It is an important grass for sub-humid subtropical regions.
Rhodes grass has an N concentration ranging from 2.7% of the DM in very young leaves to 0.5% in old leaves. The P concentration ranges between 0.1% and 0.4% depending on age of material and soil fertility. DM digestibility of green material is about 60% (ranging from 40-82%) depending on growth stage and cultivar. Crude protein digestibility can be as high as 70%. Palatability is good, but varies with cultivar. Cultivar "Katambora" is used as nematode suppressor in crops of tobacco. There are 7000-10 000 seeds/g.
A perennial, stoloniferous (varies with cultivar), creeping or occasionally tufted grass, 0.5-2 m tall. Stem fine and leafy, erect or ascending, occasionally rooting at the lower nodes. Leaf-sheath glabrous except near the blade; ligule about 1 mm long, including a fringe of short hairs, with long hairs on the blade close to it; leaf-blade flat, rarely involute, (15-)25-50 cm × (1.5-)3-9 mm, tapering towards the apex, margins rough, glabrous except near the base, lateral veins strongly developed. Inflorescence consisting of (3-)6-15(-20) digitate ascending to spreading spikes 4-15 cm long, all attached at the top of the culm, or a few a little below the others; spikelets green or purplish, about 3.5 mm long; florets 3(-4), with usually one hermaphrodite (lemma with an awn of 1-10 mm long), one male (awn 1.5-5.5 mm) and one rudimentary; sometimes all florets are hermaphrodite and fertile.
Growth and development
Seed germination is optimal between 8 and 18 months after harvest. The seed germinates quickly (in 1-7 days, depending on temperature) and seedlings establish rapidly. The seedlings produce erect tillers, with stolons appearing later and these grow and branch rapidly. Widely scattered seedlings can quickly produce dense stands.
Rhodes grass is a short-day plant, flowering throughout or at the end of the growing season depending on cultivar. The caryopsis is fully ripe 23-25 days after flowering.
Other botanical information
Most cultivars are selected from natural stands. Diploid cultivars are fine-stemmed, fine-leaved and less vigorous than tetraploid cultivars which are robust and vigorous.
Giant Rhodes grass (tetraploid), released as cultivar "Callide" in Australia is late flowering and robust, with thick stems and broad long leaves, long awns (6-9 mm) and a long tuft of hairs at the awn base.
Other Australian cultivars are "Pioneer" (diploid, with lower nutritive value than other cultivars), "Katambora" (diploid, with many tillers and good seed production), "Samford" (tetraploid, vigorous stolon development, late flowering and with high palatability). Several cultivars have also been released in Africa. "Pokot" is a bred cultivar (leafy, vigorous, late flowering and high yielding), "Nzoia" (very leafy with high seed yields), "Masaba" (quite leafy and productive) and "Karpedo" (good drought tolerance).
The natural habitats of Rhodes grass are grasslands, open or with scattered trees or shrubs, river banks, lake margins and seasonally waterlogged plains.
Rhodes grass has some drought tolerance, but less than Panicum maximum Jacq. var. trichoglume Robijns. The optimum annual rainfall for Rhodes grass is between 600-1000 mm but it can withstand a dry season of up to six months. The grass responds well to irrigation and is moderately tolerant of flooding (up to 10-15 days with less than 30 cm of water).
The optimum temperature for photosynthesis is 35 °C. The temperature range for growth is very broad, from about 0 °C to 50 °C. Rhodes grass is more tolerant of low temperatures than most other subtropical grasses.
Seed germinates best at temperatures between 20-35 °C.
The optimal daylength for growth is between 10-14 hours. Herbage yields are considerably reduced at photoperiods outside this range.
Rhodes grass is tolerant of fire, but not of shade.
Rhodes grass will grow on a wide range of soils, from heavy clays to sandy loams. Optimum pH lies between 4.5 and 7. Rhodes grass tolerates a high salinity and it can accumulate high concentrations of Na in the leaves without suffering damage.
Propagation and planting
Rhodes grass can be propagated from seed and stolons. Propagation from seed gives more rapid establishment. The seed is small and should be sown very shallow, or preferably broadcast on top of a well prepared seed-bed or rather loose rough soil, covered lightly and/or rolled. It can be sown from the air into the ashes after burning. Seed sown below a depth of 25 mm will not germinate.
Naked caryopses germinate slightly better than those enclosed in glumes. Seed purity is usually not more than 25-35%, with germination of 30-55%. The seeding rate should be 0.5-1 kg/ha of pure viable seed.
Rhodes grass grows well in mixtures with a wide range of legumes such as Stylosanthes guianensis (Aubl.) Swartz, Vigna unguiculata (L.) Walp., Medicago sativa L., Macroptilium lathyroides (L.) Urban, M. atropurpureum (DC.) Urban and Lotononis bainesii Baker and as a companion crop under wheat and maize.
Rhodes grass responds well to N and P fertilizer. On fertile soils it is usually grown without fertilization.
Diseases and pests
Most cultivars are little affected by diseases or pests, but major damage can be caused by Helminthosporium spp. in "Nzoia", causing dieback of leaves and shoot bases. "Masaba" suffers from smut caused by Fusarium gramineum giving rise to seed loss in wet years.
Rhodes grass can be grazed continuously or rotationally from 4-6 months after sowing, but high grazing pressure decreases vigour. Grazing pressure should be aimed at preventing flowering, as the nutritive value declines rapidly towards maturity.
The best time to cut for hay is just before flowering. Six harvests a year are possible with cutting intervals of 25-50 days. The best time for harvesting seed is at the early stage of seed shedding.
In North Sumatra 38 t/ha of DM has been harvested in 236 days and it was one of the highest yielding grasses tested. Seed yields range between 100-650 kg/ha. Annual liveweight gains of up to 160 kg/animal and 850 kg/ha have been recorded from well fertilized Rhodes grass pastures.
Genetic resources and breeding
A large collection of Rhodes grass germplasm is held at ATFGRC (CSIRO, Australia). Rhodes grass is cross-pollinating with a self compatibility of 1-4%. Breeding work is being done in Kenya ("Pokot") and the United States (Texas). Plants are being selected on leafiness and late flowering characteristics.
Because of its wide adaptability, ease of establishment and acceptable nutritive value, Rhodes grass will continue to play an important role in pasture improvement in subtropical regions with a pronounced dry season.
- Bogdan, A.V., 1969. Rhodes grass. Herbage Abstracts 39: 1-13.
- Bogdan, A.V., 1977. Tropical pasture and fodder plants. Longman, London and New York. pp. 77-86.
- Jones, R.J. & Jones, R.M., 1989. Liveweight gain from rotationally and continuously grazed pastures of Narok Setaria and Samford Rhodes grass fertilized with nitrogen in southeast Queensland. Tropical Grasslands 23: 135-142.
- Renvoize, S.A., 1974. Chloris. In: Polhill, R.M. (Editor): Flora of tropical East Africa. Gramineae (Part 2). Crown Agents for Oversea Governments and Administrations, London. p. 346.
- Skerman, P.J. & Riveros, F., 1990. Tropical grasses. FAO, Rome. pp. 283-288.
L. 't Mannetje & S.M.M. Kersten