Urochloa mosambicensis (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Urochloa mosambicensis (Hack.) Dandy

Protologue: J. Bot. 69: 54 (1931).

Family: Gramineae

Chromosome number: 2n= 28, 30, 42

Synonyms

Panicum mosambicense Hack. (1888).

Vernacular names

• Sabi grass (En)
• Thailand: ya sabee.

Origin and geographic distribution

Sabi grass originated in the drier (400-800 mm annual rainfall), frost-free regions of southern and eastern Africa. It has been introduced into many countries including Australia, India, Sri Lanka, Burma, Thailand, Indonesia, Fiji and Hawaii. It is used commercially and is now naturalized in northern Australia.

Uses

Sabi grass is mainly used as a forage for ruminants but can also be used for reseeding denuded areas.

Properties

Chemical composition and nutritive value of Sabi grass depend on soil fertility but young green leaves typically contain up to 2.5% N, 0.2% P and are 65-70% digestible. In the late wet season equivalent values are 1.2%, 0.15% and 55-60% respectively. Dry leaves and stems are much lower in quality and typical values are 0.5% N and 0.05% P. Sabi grass is palatable. There are 600-1000 seeds/g.

Botany

A creeping, perennial grass of variable size and growth habit usually with short stolons or often tufted. Culms smooth, more or less erect, up to 150 cm tall, 5 mm in diameter, often branching at the nodes, and sometimes rooting at lower nodes; nodes prominent, densely covered with short, silky hairs. Leaf-sheaths close, covered with erect, white, tubercle-based hairs particularly in their upper part, shorter than the internodes; ligule a rim of short (1 mm) hairs. Leaf-blade broadly linear to narrowly lanceolate, 2-30 cm × 3-20 mm, pale to bright green, hirsute on both surfaces; midrib prominent, often purplish, apex tapering to a fine point. Inflorescence composed of 3-15 racemes (3-90 mm long) on a simple common axis up to 15 cm long but often much less; spikelets are borne on the lower side of the rachis only, 3-5 mm × 1.5-3 mm; lower glume ovate-lanceolate, 3-nerved, with a single bristle 1-2 mm long; lower lemma with a conspicuous fringe of bristles 1-1.5 mm long. Caryopsis light buff or cream.

Seeds of Sabi grass germinate early in the wet season and vegetative growth continues until soil water is exhausted. Flowering commences 3-4 weeks after the start of the wet season and continues until growth ceases. Seed matures in 3-4 weeks. Leaves live for 5-25 weeks depending mainly on water supply. Plants are often short-lived (3-4 years) but new plants are formed from seedling recruitment. Cultivar "Nixon" has been developed in Australia from material introduced from Zimbabwe.

Sabi grass is closely related to and much resembles Urochloa oligotricha (Fig. & De Not.) Henrard which has a 5-nerved lower glume, but intermediates occur. Both species also resemble the South African Urochloa stolonifera (Goossens) Chippend. which is smaller and with its spikelets untidily arranged.

Ecology

Sabi grass is commonly grown in areas with 500-1200 mm annual rainfall with a pronounced warm season and a dry season of 5 to 9 months. It has poor frost tolerance and rapidly hays off when soil moisture is exhausted. In its natural habitat in Africa of wooded grassland and deciduous bushland, it occurs up to 1400 m altitude. Flower initiation occurs over a range of daylengths but it is earlier at 12 hours than 9 or 15 hours. Sabi grass is adapted to a wide range of soils but will not tolerate permanently flooded or waterlogged conditions. In Africa it is a common roadside weed and often grows in disturbed or overgrazed areas.

Agronomy

Although Sabi grass can be propagated vegetatively it is normally established from seed. Freshly harvested seed is dormant but dormancy breaks down after 9 to 12 months storage. Hammer milling to destroy the hard lemma can increase germination. Sabi grass can be readily established under a variety of sowing conditions, but is best established by sowing on or near the soil surface of a well cultivated seed-bed during the early wet season. Oversowing into undisturbed pasture is often a complete failure, or takes several years to develop into a pasture. Seeding rates range from 1-5 kg/ha.

There are no important diseases or pests of Sabi grass.

Sabi grass can be used by continuous or rotational grazing, or by cutting for feeding as fresh material or for making hay. It will stand close defoliation. Sabi grass responds to N and P and is aggressive at high fertility. It combines well with legumes and is a common associate grass for Stylosanthes spp. Sabi grass produces 1-8 t/ha of DM per year depending on seasonal conditions, soil fertility and associate species.

Genetic resources and breeding

There is wide variation in Sabi grass for morphological and agronomic characteristics. The collection held at ATFGRC (CSIRO, Australia) mainly came from South Africa.

There are no active breeding programmes and improvement will depend on selection from natural populations. Important objectives to date have been adaptability to a range of environments, yield and quality.

Prospects

Sabi grass is an effective colonizing, palatable, and grazing-tolerant forage of reasonable quality suited for sowing in the drier regions of South-East Asia. It is recommended for use in the "Three Strata Forage System" in drier areas of Indonesia.

Literature

• Bogdan, A.V., 1977. Tropical pasture and fodder plants. Longman, New York. pp. 295-296.
• Burt, R.L., Williams, W.T., Gillard, P. & Pengelly, B.C., 1980. Variation within and between some perennial Urochloa species. Australian Journal of Botany 28: 343-356.
• Clayton, W.D. & Renvoize, S.A., 1982. Urochloa. In: Polhill, R.M. (Editor): Flora of tropical East Africa. Gramineae. A.A. Balkema, Rotterdam. Part 3. pp. 600-607.
• Devendra, C. (Editor), 1990. Shrubs and tree fodders for farm animals. Proceedings of a workshop held in Denpasar, Indonesia, 24-29 July 1989. IDRC, Ottawa, Canada. 349 pp.
• McIvor, J.G., 1985. The growth of Urochloa accessions in grazed swards with Stylosanthes near Townsville, north Queensland. Australian Journal of Experimental Agriculture 25: 61-69.
• Oram, R.N., 1990. Register of Australian herbage plant cultivars. CSIRO, Australia. pp. 87-88.
• Whiteman, P.C. & Gillard, P., 1971. Species of Urochloa as pasture plants. Herbage Abstracts 41: 351-357.

Authors

J.G. McIvor