Paspalum dilatatum (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Paspalum dilatatum Poiret

Protologue: Lamk, Tabl. Encycl. 5: 35 (1804).

Family: Gramineae

Chromosome number: 2n= 40 (sexual, yellow-anthered biotype), 45 (interspecific hybrid), 50 (apomict, common cultivar), 70 (hybrid)

Synonyms

Paspalum platense Sprengel (1825), P. ovatum Trinius (1826), Digitaria dilatata (Poiret) Coste (1906).

Vernacular names

• Dallis grass, Australian grass, paspalum (Australia)(En). Paspalum dilaté (Fr)
• Indonesia: rumput australi
• Philippines: lawa-lawa (Tagalog), halanaw (Bikol), sakata (Visaya)
• Thailand: ya-daenlit
• Vietnam: co' san dep.

Origin and geographic distribution

Dallis grass is native to the humid subtropics of Brazil, Argentina and Uruguay. Now it is widely distributed in coastal subtropical Australia, the south-eastern part of the United States, India, some African countries, Madagascar, Hawaii, Fiji and Malesia.

Uses

Dallis grass is used in pastures for grazing, hay and silage-making. It is better suited for grazing than for cutting, because of its tendency to lodge. It can also be sown into the stubble after a rice crop. Dallis grass gives excellent protection against erosion.

Properties

Dallis grass is very palatable at early stages of growth, but this decreases rapidly with increasing age. The N concentration of green material ranges from 0.8-3.8% of the DM and the DM digestibility between 50-63%, both depending on plant maturity, soil fertility and environmental conditions. There are 570-750 seeds/g.

Description

A leafy, tufted perennial with clustered stems arising from very short, creeping rhizomes, forming a sod under grazing, rooting up to 1.2 m deep. Stem ascending to erect, 50-150 cm tall, rooting at the nodes when in contact with the soil. Leaf-sheath slightly keeled, basal ones often pilose; ligule bluntly triangular, up to 6 mm long; leaf-blade linear, flat, (5-)12-16(-39) cm × 3-13 mm, usually with some up to 6 mm long hairs at the base of the ligule, otherwise glabrous. The inflorescence consists of 3-5(-9) alternate racemes, the lowest 5-13 cm long, the others gradually shorter upwards; spikelets paired, usually imbricate, in rows along one side of a flattened axis, ovate, 3-4 mm long; lower glume absent; upper glume as long as the spikelet, with a fringe of white, ca. 2 mm long hairs along the margin framing the spikelet; lower floret with sterile lemma; upper floret bisexual. Caryopsis suborbicular, plano-convex, up to ca. 2 mm long.

Growth and development

Early growth is slow, but once established growth is vigorous and many leaves are produced in a short time. Dallis grass has its fastest growth rate early in the growing season, but growth slows down during mid-summer and autumn. During the cool period in subtropical regions and at higher altitudes the plants are dormant. Flowering occurs throughout the growing period and seeds scatter as soon as they are ripe. With declining soil fertility, the vigour of Dallis grass declines and it is then often invaded by Axonopus affinis Chase.

Other botanical information

P. dilatatum can be divided into two varieties, var. dilatatum and var. pauciciliatum Parodi. The latter has 2 n = 40 chromosomes and is more prostrate. It has slightly smaller and less hairy spikelets, more spikelets per raceme and its lemma and palea have three veins compared with nine in var. dilatatum. This variety is better adapted to light and poorly drained soils than common Dallis grass. Important cultivars of var. dilatatum are "Raki" from New Zealand, "Charu" from Uruguay and "Natsugumo" from Japan.

Ecology

Dallis grass is adapted to permanently humid subtropical climates (10-12 humid months) with over 1000 mm annual rainfall mainly during the warm season. Optimum temperatures for leaf growth, tillering and flowering are 30 °C, 27 °C and 22.5 °C respectively. Seed production is inhibited at temperatures below 13 °C. Dallis grass grows on lowlands as well as at altitudes up to 2000 m. It is one of the most frost tolerant subtropical grasses. It is a long-day plant, with an optimal daylength of 14 hours. Dallis grass has little shade tolerance. It requires fertile soils and performs best on alluvial soils or basaltic clays. Optimum pH(H₂O) is between 5.5 and 7.0. Dallis grass does not tolerate salinity.

Propagation and planting

Dallis grass seed has some post-harvesting dormancy which can be broken by removal of the glumes. It is usually sown at a seeding rate of 6-10 kg/ha, either broadcast on the surface with a light covering, or drilled to a depth of 1-1.5 cm, preferably just before the start of the rainy season. After a rice crop it can be sown into the stubble without seed-bed preparation. Because Dallis grass is a slow starter, it is often established in mixtures with rapidly growing grasses such as Chloris gayana Kunth, which can compete better with weeds. Other species growing in association with Dallis grass are Trifolium repens L., T. semipilosum Fresen. and Vigna parkeri Baker.

Husbandry

Dallis grass tolerates high stocking rates and frequent defoliation, which also prevents it from flowering and consequently ergot infection, which can cause poisoning. It can be grazed continuously or rotationally. Lenient grazing, not shorter than 5-8 cm, results in up to three times more forage than heavy grazing. Dallis grass responds well to fertilization.

Diseases and pests

Dallis grass is very susceptible to ergot ( Claviceps paspali ). This fungus infects the inflorescence and excretes a substance which is toxic to cattle and can occasionally cause abortion. Ergot is also the most important factor affecting seed quality. Other diseases are anthracnose ( Colletotrichum graminicola ) and leaf blight ( Helminthosporium micropus ), but these are generally unimportant. Dallis grass pastures are sometimes invaded by white-grubs ( Lepidiota caudata and Rhopaea paspali ), which destroy the roots and reduce productivity.

Harvesting

For hay or silage making Dallis grass can be cut every 4-6 weeks, preferably before the grass is 30 cm tall and before flowering. Seed is best harvested about 21 days after flowering when inflorescences are brown, but before seed shattering becomes severe.

Yield

Total DM yield ranges from 3-15 t/ha, depending on soil fertility or fertilization. High animal production can be obtained from Dallis grass under good management. In southern Australia stocking rates of 25 sheep/ha can be maintained. With irrigation, optimal fertilization and by including winter-growing species, milk yields of 10 000 kg/ha per year have been recorded.

Seed yields are variable: 90-500 kg/ha.

Handling after harvest

Seed should be dried immediately after harvest at 60 °C or spread in a thin layer and dried to 7-10% moisture content.

Genetic resources and breeding

A germplasm collection of Dallis grass is held at ATFGRC (CSIRO, Australia). Seed is produced in Australia, the United States and Uruguay. Dallis grass is mainly apomictic by apospory and pseudogamy. The sexual type is less common. Crossing an apomict with a female sexual species gives an interspecific hybrid with 2 n = 50. The first generation reproduces sexually and seed set increases progressively.

Breeding work is being done to increase ergot and anthracnose resistance.

Prospects

Due to its palatability, productivity, its ability to combine with Trifolium repens and to withstand heavy grazing, Dallis grass is a desirable species, particularly in areas where it is naturalized. However, it requires careful management because of its susceptibility to ergot.

Literature

• Bogdan, A.V., 1977. Tropical pasture and fodder plants. Longman, London and New York. pp. 197-202.
• de Koning, R. & Sosef, M.S.M., 1985. Malesian species of Paspalum. Blumea 30: 293-294.
• Shaw, N.H., Elich, T.W., Haydock, K.P. & Waite, R.B., 1965. A comparison of seventeen introductions of Paspalum species and naturalised P. dilatatum under cutting at Samford, south-eastern Queensland. Australian Journal of Experimental Agriculture and Animal Husbandry 5: 423-432.
• Skerman, P.J. & Riveros, F., 1990. Tropical grasses. FAO, Rome. pp. 579-584.
• Watson, V.H. & Burson, B.L., 1985. Bahia grass, Carpet grass and Dallis grass. In: Heath, M.E., Barnes, R.F. & Metcalf, D.S. (Editors): Forages, the science of grassland agriculture. Mississippi, United States. pp. 255-262.

Authors

L. 't Mannetje & S.M.M. Kersten