Narrowleaf Carpetgrass - Turf Grass

Scientific name: Axonopus fissifolius, formerly A. affinis; (Raddi) Kuhlm.

Synonyms: Axonopus affinis Chase; Paspalum fissifolium Raddi

Family/tribe: Poaceae (alt. Gramineae) subfamily: Panicoideae tribe: Paniceae.

Common names: Caratao grass, carpet grass, common carpet grass, Louisiana grass (USA); mat grass, narrow-leaved (narrowleaf) carpet grass, durrington grass (Australia); teppichrasengras (German); grama-missioneira (Brazil); zacate amargo (Mexico).

Characteristics: Closely related to broadleaf carpetgrass. While its leaf blades are appreciably narrower (50-60%) than those of broadleaf carpetgrass, narrowleaf carpetgrass is still a coarse-textured species. It is more drought tolerant and better suited to drier shallower soils than broadleaf carpetgrass, and is typically the dominant species in low soil fertility run-down dairy pastures in southern Queensland and northern New South Wales. However, as a turfgrass, it forms a moderately dense sward of medium quality.

Morphological description: Shallow-rooted (>90 % of roots in the 0-5 cm layer) perennial, initially forming shortly rhizomatous tufts that quickly develop vigorous stolons with relatively short, glabrous oval-section (± 2 x 1.5 mm) internodes; forms a dense mat with foliage 15-30 cm tall, and flowering culms mostly 30-60 cm; can be mowed to a turf. Leaf sheath compressed, keeled, largely glabrous; ligule a fringed membrane 0.5 mm long; blades 4-6 (-8) mm wide, and 5-15 (-28) cm long, flat or folded, glabrous except for sparse spreading hairs on the lower margins of young leaves, bluntly acute at the tip. Inflorescence a panicle comprising 2 or 3 (rarely 4-7) slender, spikelike racemes, paired or sub-digitately arranged on a long slender peduncle; racemes (2-) 3-7 (-10) cm long; spikelets, 1.7-2.8 mm long, 1 mm broad, inserted alternately either side of a flattened rachis; caryopsis tan to pale brown, compressed-ellipsoid to lenticular , 1.4-1.8 mm long. 2.5-3 million seeds per kg. Differs from compressus in having more slender culms and stolons, narrower leaves and shorter, more obtuse spikelets.

Distribution: Native to: North America: South and central USA, Mexico. Central America and Caribbean: Belize, Costa Rica, El Salvador, Grenada, Guatemala, Honduras, Nicaragua, Panama. South America : Argentina, Bolivia, Brazil, Colombia, Ecuador, Guyana, Paraguay, Uruguay, Venezuela.

Occurs on low, flat areas in humid and sub-humid warm temperate to tropical woodland and savannah .

Naturalised in: Africa, Asia, Australia and the Pacific Islands.

Uses/applications

Used as a permanent pasture, ground cover, and turf in moist, low fertility soils. It is generally too low growing to be useful in cut-and-carry systems or for fodder conservation .

Strengths: Grows on poor soil; Good ground cover; Tolerates heavy grazing; Is at its best in warm temperatures (27 - 32°C) with long days (15hrs).

Limitations: Poor drought tolerance; Very low nutritive value; Low dry-matter yield; Low tolerance of salinity; Short growing season.

Ecology

• Soil requirements: Adapted to well to moderately drained sandy or sandy-loam soils, but also to light clays and peats, flourishing in soils too infertile for Paspalum dilatatum . Best in acid soils with pH (4.3-) 5-6 (-7), becoming chlorotic above pH 7. Low tolerance of salinity (<4 dS/m).
• Moisture: Mostly found in areas with an annual rainfall of (750-) 1,000-2,000 (-4,000) mm. It is not very drought -tolerant, although more so than compressus , colonising hilly, as well as flat country. While preferring moist soils, it does not withstand prolonged flooding or permanently swampy conditions.
• Temperature: Occurs from sea level to >3,000 m asl, and from near the equator to about 35° latitude, representing a significant range in average annual temperatures from (13-) 17-27°C. Top growth is greatest between 27 and 32°C, and with a day length of 15 hours. Temperatures below 13°C inhibit flowering. Although found in the tropics, it appears to be best adapted to the subtropics. It is found further south than compressus in Australia. Tops are burnt off by heavy frost, but plants recover with the onset of warmer, moist conditions.
• Light: Moderately shade tolerant but less so than compressus .
• Reproductive development: A. fissifolius flowers over a wide range of daylengths, flowering throughout the growing season in most environments, with a peak between 12 and 14 hours.

Guidelines for the establishment and management

• Establishment: A.fissifolius can be established vegetatively from runners/sprigs, or from seed. Seedlings develop fairly slowly, so seed is best broadcast onto, or shallowly sown into, a well-prepared seedbed to give the best chance of establishment. Subsequent rolling helps maintain soil moisture and ensures close contact between soil and seed. Choice of sowing rate depends on quality of seedbed and the rate of ground cover required. With a good seedbed where rate of cover is not an issue, 2-3 kg/ha of seed is adequate, while with a less well prepared seedbed or where rapid cover is important, 6-12 kg/ha may be necessary.
• Fertiliser: Low rates of nitrogen can help to extend the otherwise fairly short growing season, and to maintain the sward in a vegetative state. It does not appear to be very responsive to phosphorus, growing well in low P soils. A. fissifolius is less responsive to applied nitrogen than is Paspalum dilatatum with which it is often found growing. Mixed swards of the two species become P. dilatatum dominant with continued applications of nitrogen.
• Compatibility (with other species): As soil nitrogen levels decline and under regular defoliation , fissifolius can successfully invade pastures based on more fertility demanding species such as Paspalum dilatatum , Cynodon dactylon , and Setaria sphacelata . It is not very competitive, and can be grown with stoloniferous or rhizomatous legumes.
• Companion species: Grasses: Paspalum dilatatum . Legumes: Aeschynomene falcata , A. villosa , Arachis glabrata , A. pintoi , Lotus uliginosus , Trifolium repens, T. semipilosum , Vigna parkeri .
• Pests and diseases: It is not subject to any major diseases or insect pests, although it is attacked by grass webworm (Herpetogramma licarsisalis, Lepidoptera, Pyralidae), usually during rainy weather, and is affected by Axonopus chlorotic streak, a leaf hopper transmitted virus in New Guinea. Nematodes including Meloidogyne sp., Pratylenchus pratensis and Radopholus similis can cause serious injury in stands on well-drained soils.
• Ability to spread: A.fissifolius produces abundant light seed that is readily spread by water movement and vehicles, and through the dung of grazing animals. Under favourable conditions, it spreads rapidly by stolons.
• Weed potential: It is usually insufficiently aggressive to be considered a serious weed in fertile soils. However, it has become a weed in some areas by virtue of its ability to colonise low fertility soils.
• Toxicity: No record of toxicity.
• Seed production: Commercial seed is mostly produced in the humid sub-tropics, mostly as “opportunity” crops. While in most other grass seed crops, stands are “cleared off” to produce a synchronous crop, and nitrogen fertiliser applied to promote tillering, this is generally not followed for seed crops of this species. Crops ripen unevenly and are mostly harvested non-destructively, providing about 50 kg/ha of seed per pass. Fresh seed should be dried at no more than 35ºC, to avoid damage to the seed.
• Herbicide effects: Susceptible to DSMA, bentazon, bromoxynil, 2,2-DPA and metsulfuron methyl. Tolerant of diclofop methyl.