Digitaria decumbens Stent

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Graminae

Common names

Pangola grass (United States, Australia), pasto pangola (Peru), pangola digit grass (Florida).

Description

A stoloniferous perennial which differs from D. pentzii mainly in having the culms much branched, usually decumbent, and often rooting from the lower nodes, the spikelets 2.5-3 mm long and quite glabrous, the hairs on the upper glume and lower lemma being short, fine and inconspicuous. D. decumbens is based on a plant from the Nelspruit district of the Transvaal. Subsequently plants were referred to it that were cultivated in Pretoria as the "Pangola River" strain of woolly finger grass (Chippendall, 1955).

Distribution

Originated in the Transvaal and now introduced into most tropical countries.

Season of growth

Summer, with a growth period of up to seven months. It commences growth in November and slows down in March in south-east Queensland.

Altitude range

In Hawaii, sea-level to 1 500 m.

Rainfall requirements

The mean rainfall is 900-1 975 mm (Russell & Webb, 1976). In South Africa it grows well under the 625-750 mm summer dominant rainfall on moist, fertile, well-drained soils but is better suited to rainfalls of 1 000- 1 200 mm in coastal regions.

Drought tolerance

It will survive droughts fairly well if established, but will not be productive.

Soil requirements

Pangola grass will grow over a wide range of soils on wet sands or heavy clays and at low fertility levels. It will grow on poorer soil than Paspalum dilatatum and Pennisetum clandestinum but in low fertility soils is not very attractive to hungry stock.

Ability to spread naturally

Once pangola grass is established it spreads very rapidly by stolons. It does not produce viable seeds.

Land preparation for establishment

An initial ploughing or other soil disturbance is required so that sprigs can be incorporated in a loose soil.

Sowing methods

As pangola grass does not produce viable seed, propagation is effected by sprigs or roots. For large areas, the quickest method is to cut the vegetative plant material in a chaff-cutter or forage harvester adjusted to provide plant pieces with a few nodes, broadcast this material over the ploughed field and disc-harrow it in, or simply broadcast whole runners and disc the area. Hand planting of roots about 1 m apart will soon give a good cover. A small nursery area established ahead to provide material for future enlarged planting is a sound approach.

Vigour of growth and growth rhythm

Pangola grass grows vigorously when established.

Response to defoliation

Pangola grass tolerates heavy grazing. Extremely heavy grazing is not harmful if the grass is allowed to grow again to a height of 30-45 cm afterwards (Bennett, 1973).

Grazing management

In Jamaica, Creek and Nestel (1965) found that pangola grass grazed at 32-day intervals produced more dry matter and more liveweight gain than when grazed at 40-day intervals. In the United States it is suggested that it be grazed rotationally, allowing one week's rest during grazings in midsummer and two to three weeks during the remainder of the growing season (Bennett, 1973). In Colombia, Crowder, Michelin and Bastidas (1964) recommended applying 84-114 kg N/ha after every cut at approximately two- monthly intervals. Recovery rates for nitrogen were 50-75 percent.

Dry-matter and green-matter yields

At Beerwah, south-east Queensland, under an annual summer dominant rainfall or 1 075 mm, it produced a mean annual yield of 10 565 kg/ha per year, fully fertilized (Evans, 1967a) and grows at the rate of 113 kg DM/ha per day in summer, but only produces 2.25 kg DM/ha per day in winter (Evans & Hacker, 1980). At South Johnstone in north Queensland (lat. 17°6'S, altitude 580 m and rainfall 900 mm) 28 282 kg DM/ ha per year were obtained from five cuttings from a pasture fertilized with 220 kg nitrogen, 22 kg phosphorus and 55 kg potassium per hectare per year. It outyielded Panicum maximum cv. Hamil and Brachiaria ruziziensis, but yielded less than Brachiaria decumbens and B. mutica (Grof & Harding, 1970).

Suitability for hay and silage

It cures rapidly in dry weather and makes excellent hay when cut and cured before it gets too stemmy (Wheeler, 1950). It makes successful silage in Florida.

Value as a standover or deferred feed

When pangola grass matures, its feeding value declines and standover feed, while providing roughage, is not very nutritious.

Toxicity

No toxicity has been recorded with this grass.

Cultivars

There is only one cultivar in Australia. In Florida, United States, a slender-stemmed type known as 'Leesburg No. 5' has achieved some success (Nester & Creek, 1962) and also cv. Transvala (Gaskins & Sleper, 1974).À

Diseases

Pangola grass has been seriously attacked by a rust (Puccinia oahuensis) in many areas causing agronomists to look for a replacement grass among the Digitaria species (Evans, 1972). In Fiji it is affected by a stunt virus which is also serious in Florida.

Main attributes

Its rapid cover, nutritious growth in the presence of nitrogen, ability to establish on poor soils and withstand heavy stocking, and its ability to combine with Lotononis bainesii.

Main deficiencies

Its lack of seed production and its susceptibility to rust, its short growing season and its aggressiveness in relation to legumes other than Lotononis bainesii.

Optimum temperature for growth

The mean temperature where it grows is 19- 24°C (Russel & Webb, 1976). In Hawaii it grows well between 25 and 40°C (Whitney & Green, 1969). It grows actively above 26.5°C (Bryan & Sharp, 1965).À#S

Minimum temperature for growth

The mean temperature of the coldest month in areas where it normally grows is 7-15°C (Russell & Webb, 1976). Blue, Gammon and Lundy (1961) suggested a 10°C minimum in Florida, and Bryan and Sharpe (1965) about 15°C in south-east Queensland.JDP

Frost tolerance

It is susceptible to frosts, but generally recovers during subsequent warm weather.

Latitudinal limits

The mean latitude is given as 21-30°N or S by Russell and Webb (1976).

Response to light

It showed low tolerance to 50 percent light under coconuts (Reynolds, 1978).

Ability to compete with weeds

Pangola grass quickly suppresses weeds.

Pests

In Florida the yellow sugar-cane aphid (Sipha flava) is a major pest (Bennett, 1973; Oakes, 1978). Another aphis (Schizaphis hypersiphata) is also troublesome, and the crabgrass leaf beetle (Lemma rufotincta) less damaging. The sting nematode may be serious. Minor pests are the lawn armyworm (Spodoptera mauritia) and the sod webworm (Herpetogramma licarsisalis) (Broadley & Rogers, 1978). Heavy aphis populations have caused severe damage in the wet tropics (Teitzel & Middleton, 1979). Natural predators such as ladybirds and hover flies exert some control.

Palatability

Excellent when the material is young and vigorous. It is usually neglected in favour of other grasses when it becomes old and stemmy.

Response to photoperiod

It is a long-day plant and flowers in 14 hours of daylight (Degras, Mathurin & Félicité, 1974).

Chemical analysis and digestibility

The feeding value of pangola grass is high, but animal intake near maturity can be limited by protein deficiency (Minson, 1967) unless a late application of nitrogen fertilizer is given or it is grown with a legume. Bryan and Sharpe (1965) reported a range of 3.9 to 11.6 percent crude protein in the dry matter. In Costa Rica, analysis of material at floral initiation revealed 11.81 percent crude protein, 30.2 percent crude fibre, 36.3 percent nitrogen-free extract, 2.5 percent ether extract and 9.2 percent ash in 10 percent moisture material. Sulphur fertilization of pangola grass through superphosphate increased the nutritive value of pangola grass by overcoming a simple sulphur deficiency when diets contained less than 0.17 percent sulphur (Rees & Minson, 1976).

Tolerance to flooding

It can withstand temporary, but not sustained, flooding.

Fertilizer requirements

Pangola grass responds markedly to nitrogen when matched with adequate phosphorus, potash and trace elements. Normal applications of nitrogen under irrigation are about 300 kg/ha per year. At Palmira Experiment Station in the Cauca Valley, Colombia, dry-matter production increased in linear fashion with each additional increment of nitrogen up to 224 kg/ha and in a curvilinear manner with higher applications. The critical value for phosphorus in the dry matter at the immediate preflowering stage is 0.16 percent. It can fix up to 65 kg N/ha per day (Weier, 1976). It tolerates high aluminium (Spain, 1979).

Compatibility with other grasses and legumes

Under suitable conditions for its own development, pangola grass dominates all other species. It combines well with the legume Lotononis bainesii (Bryan, 1961), as both stand heavy grazing. It can also grow with Centrosema pubescens. In Florida, Kretschmer (1965, 1966) has grown it satisfactorily with Stylosanthes humilis and Macroptilium atropurpureum (siratro) where addition of nitrogenous fertilizer is low.

Genetics and reproduction

Pangola grass is highly male sterile because lagging chromosomes produce unbalanced nuclei in the pollen, and female sterile because meiosis fails to progress beyond the leptolene stage. Only one plant which has produced seed has been observed (Sheth, Yu & Edwardson, 1956). It is an aneuploid ­ 2n= 17 (Hutton, 1970).

Animal production

With dressings of 448 kg and 896 kg N/ha on the moist Beerwah (south-east Queensland) environment, pangola grass gave annual live- weight gains in cattle of 1 220-1 340 kg/ha (Bryan & Evans, 1967). At Parada, in north Queensland, a live-weight gain of 2 990 kg/ha/year was obtained from grazing irrigated pangola grass fertilized with 672 kg N/ha per year (Ebersohn & Lee, 1972). In the Ord River valley in northern Australia, a maximum live-weight gain of 1 330 kg/ha a year was obtained from 11.5 weaner steers per hectare and there was no increase with increasing dressings of nitrogen from 300 kg to 800 kg/ha per year (Blunt, 1978). A figure for live-weight gains of beef cattle of about 1 300 kg/ha per year has also been obtained in Florida (Motta, 1968), Puerto Rico (Caro-Costas, Vicente-Chandler & Burleigh, 1961; Caro-Costas, Vicente-Chandler & Figarella, 1965), Beerwah, Queensland (Evans, 1969) and Ayr, north Queensland (Deans et al., 1976). In Brazil, Aronovich, Serpa and Ribeiro (1970) obtained an average live-weight gain per hectare per year over four years of 349 kg with pangola alone, 410 kg with a mixture of pangola grass and the legume Centrosema pubescens and 531 kg/ha from a pangola grass pasture fertilized with 100 kg N/ha per year. At Turrialba, Costa Rica (605 m altitude, 2 688 mm rainfall) a herd of 50 cows grazing a pangola grass pasture at intervals of 21 days at 2.67 beasts per hectare produced 6 014 kg milk per hectare. The pasture was fertilized with 100 kg urea per hectare, 150 kg potassium chloride and 80 kg/ha triple superphosphate in April, followed by two additional applications of 200 kg urea per hectare at intervals of four months (Blydenstein et al., 1969). In the West Indies, pangola grass fertilized with 330 kg N/ha produced an annual liveweight gain of 1 157 kg/ha, compared with unfertilized pasture production of 357 kg/ha (Oakes, 1960).p#

Further reading

Aronovich, Serpa & Ribeiro, 1970; Bryan & Evans, 1967; Bryan & Sharpe, 1965; Nestel & Creek, 1962.p

Value for erosion control

Wherever pangola grass can be successfully grown it will effectively control erosion.

Tolerance to salinity

Fair.

Sowing time

Preferably during the rainy season so that the planting material will root down quickly.