Ischaemum magnum (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Ischaemum magnum Rendle

Protologue: J. Bot. 32: 102 (1894).

Family: Gramineae

Chromosome number: 2n= unknown

Synonyms

Ischaemum laeve Ridley (1905).

Vernacular names

• Malaysia: rumput melayu, rumput tembaga kasar.

Origin and geographic distribution

I. magnum occurs in restricted areas of Peninsular Malaysia, Singapore, Borneo, Thailand and Burma between latitudes 20°N and 5°S.

Uses

I. magnum is not well recognized as a forage grass for grazing but its young growth is readily eaten by free-ranging cattle and goats.

Properties

Herbage obtained from cutting experiments contained 0.6-1.3% N, 0.10-0.20% P and 1.2-2.6% K depending on the age of regrowth and soil fertility. There are about 400 seeds/g.

Botany

A perennial tussock grass with stout culms, up to 2 m tall and a strong root system. Leaf-sheath terete, up to 16 cm long, fringed with fine hairs; ligule a prominent membrane fused with the auricles, 4 mm long; leaf-blade large, lanceolate-acuminate, up to 30 cm × 1.8 cm, abruptly narrowed to a petiole at the base, often hairy near the base, the margins scabrid. Inflorescence composed of two terminal, well-exserted, one-sided racemes closely appressed together, 9-18 cm long, usually without, seldom with small awns; each raceme with spikelets arranged in pairs, one sessile, one pedicelled, on one side of a triangular hairy rachis; spikelets similar but the pedicelled spikelet has a lower glume with a narrow wing all down one side.

It flowers and sets seed throughout most of the year, but the peak flowering time in Malaysia is in October-November. The maturation of the spikelets is not synchronized and seeds easily shatter. This makes seed harvesting difficult and also means that it has the potential to be a weed in cultivated areas.

Ecology

I. magnum is found abundantly in both full sunlight and under shade and is a common component of natural pastures. The optimum temperature for growth in its natural habitat is 30-35 °C (day) and 22-24 °C (night) with 12 hours daylength varying by only 30 minutes throughout the year. It grows in areas receiving 2000-4000 mm annual rainfall. It is highly tolerant of flooding and waterlogged conditions and hence is found in ditches and canals. It is adapted to a wide range of soils ranging from sands, marine peats to heavy clays. It grows aggressively and can compete with common weeds including Imperata cylindrica (L.) Raeuschel. It can also survive short, dry periods.

Agronomy

I. magnum can be established by seed or by vegetative propagation. Seed is sown into a prepared seed-bed and usually about 30% germinates. Rooted tillers are planted about 1 m apart in wet soil. Seedling growth is slow, but once established, the plants are able to regrow despite severe slashing or annual burning.

No serious pests and diseases have been recorded but predation by birds reduces seed set.

Herbage is well grazed by cattle when it is young but palatability declines towards maturity. Grass swards containing I. magnum are usually burnt yearly to obtain new growth. It is compatible with Centrosema pubescens Benth. and Stylosanthes guianensis (Aublet) Swartz.

Legumes such as Centrosema pubescens, Desmodium heterocarpon (L.) DC. ssp. ovalifolium (Prain) Ohashi and Stylosanthes guianensis tend to dominate the grass under continuous grazing. Herbage can be cut for stall feeding but it is usually grazed by free-ranging animals. Under heavy grazing or regular cutting it develops a more prostrate growth habit.

In a 3-year cutting trial in Malaysia, the mean annual DM yield of pure swards of I. magnum, fertilized with 200, 25 and 190 kg/ha of N, P and K, respectively, and cut every 8-10 weeks, was 13.7 t/ha. When grown with the legumes Centrosema pubescens, Pueraria phaseoloides (Roxb.) Benth. and Macroptilium atropurpureum (DC.) Urban, total DM yields were about 10 t/ha. These DM yields were similar to those from comparable swards of Brachiaria decumbens Stapf, although the total yield of N from I. magnum swards was slightly less. Yields declined markedly when the cutting interval was reduced to 4 weeks.

Genetic resources and breeding

It is unlikely that any germplasm collections are being maintained and there are no selection or breeding programmes with I. magnum.

Prospects

I. magnum has many advantages including hardiness, persistence and productivity in harsh environments, as well as acceptability by livestock. Research into all aspects of the agronomy of I. magnum would be warranted.

Literature

• Gilliland, H.B., Holttum, R.E. & Bor, N.L., 1971. Grasses of Malaya. In: Burkill, H.M. (Editor): Flora of Malaya. Vol. 3. Government Printing Office, Singapore. pp. 261-262.
• Ng, T.T. & Wong, T.H., 1976. Comparative productivity of two tropical grasses as influenced by fertilizer nitrogen and pasture legumes. Tropical Grasslands 10: 179-185.
• Skerman, P.J. & Riveros, F., 1990. Tropical grasses. FAO, Rome. pp. 478-479.

Authors

T.T. Ng