Stylosanthes humilis


Scientific name

Synonyms

Astyposanthes humilis (Kunth) Herter
Stylosanthes figueroae Mohlenbr.
Stylosanthes sundaica Taub.

Family/tribe

Family: Fabaceae (alt. Leguminosae) subfamily: Faboideae tribe: Aeschynomeneae subtribe: Stylosanthinae. Also placed in: Papilionaceae .

Common names

townsville stylo, townsville lucerne (English);  luzerne de townsville (French);  townsvilleluzerne (German);  alfafinha-do-nordeste, erva-de-orelha, alfalfa de townsville, alfalfa selvagem (Portuguese-Brazil);  alfalfa estilosante (Spanish);  magsaysay lucerne (Philippines);  thua-satailo (Thailand).

Morphological description

Prostrate to erect herbaceous annual 5-50 cm (-70 cm) tall, usually with short white hairs along one side of the stem and often scattered short bristles on stem and nodes.  Prostrate stems in contact with moist soil may develop adventitious roots away from the taproot.  Leaves trifoliolate, leaflets lanceolate or elliptical, acute, terminal leaflet to 15 mm long and 3.5 mm wide;  both surfaces more or less glabrous, with bristles 3-5 mm long on the petioles, rachis and stipuleInflorescence comprises several short, ovoid, crowded spikes with 5-15 flowers in each spike;  spikes hirsute, without axis rudiment;  flowers with bright yellow corolla, and standard 3-4 mm diameter.  Six or more pods produced in each seed head.  Pod (lomentum), hairy with two articulations;  the upper articulation fertile, the lower sterile.  The beak on the upper articulation is 1.5-3 times the length of the upper articulation and strongly uncinate to coiled;  upper articulation (including the beak) 7-10 mm long.  Seeds yellowish to brown and purplish black, with approximately 400,000-500,000 seeds or 275,000-300,000 seed-in-pod /kg.

S. sundaica, a tetraploid perennial with a different pod structure from other S. humilis , and which grows on neutral to alkaline soils in Bali and Timor, may in fact be a distinct species.

Distribution

Native to:
North/Central America:  Costa Rica, southern Mexico, Nicaragua, Panama.
Caribbean:  Cuba.
South America:  Venezuela, northern and central Brazil, Colombia.  May be only naturalised, not native, in Brazil.

Naturalised in:
Malesia and northern Australia.

Two morphological-agronomic groups recognised, from:
1. Brazil, Colombia and Dominican Republic (native or adventive), and Australia, Côte d'Ivoire, Kenya, Philippines, Tanzania, and USA (all adventive).
2. Costa Rica, Mexico, Nicaragua, Venezuela.

Uses/applications

Component of permanent pasture.  Mostly for grazing;  generally too low for cut and carry.  Makes quite good hay , particularly if the stand has been fertilised with phosphorus, and is not too badly affected by anthracnose.

Ecology

Soil requirements

Occurs over a wide range of soil textures from gravel to clay but predominantly on lighter soils.  In cultivation, prefers sands and sandy loams, but will grow on hard setting and heavier soils, not necessarily well drained.  PH range at collection sites varies from 5.0-6.5.  Mostly naturalised on at least slightly acid soils.  Nodulates effectively down to pH 4.5, or pH 4.0 if the calcium supply is adequate.  Has tolerance of high levels of available Al and Mn, and fair tolerance of salinity.

Moisture

Top

Occurs in tropical areas with 400 mm rainfall and pronounced dry season to areas with rainfall >3,000 mm and a short dry season.  Adventive populations have developed in areas with rainfall varying from about 500-1,500 mm, although many of the populations in more humid areas have succumbed to the disease anthracnose, caused by Colletotrichum gloeosporioides.  Although it persists, it does not add significantly to animal production in lower rainfall areas below about 800 mm.  Relatively insensitive to dry conditions once established.  Survives drought through being annual and setting copious amounts of mostly hard seed, and developing a large bank of soil seed.  Survives short periods of waterlogging but cannot withstand flooding.

Temperature

In its native or naturalised range in the Americas, S. humilis extends from about latitude 3-23º, and from near the equator to 28º elsewhere.  Altitudinal range extends from near sea level in the tropics and subtropics to 1,500 m asl in the tropics.  This represents an average annual temperature range of 14-28ºC, in frosted and non-frosted environments.  Temperatures for optimum growth range between about 27°C and 33°C day temperature .  Night temperatures below 25°C and day temperatures below 30°C inhibit dry-matter production.  Plants are killed by frost, but ripe seed is normally set before frost.

Light

Grows best in full sunlight;  should not be grown with tall grass or under trees.  Yield reduced by 47% at 74% daylight;  at 38% daylight, one third of plants die.

Reproductive development

Has short-day flowering response with a critical photoperiod of 12-14 hours, and peak flowering at 8-10 hours.  This is genetically controlled, the shorter daylength response being dominant.  After commencement of flowering, the main stem often tends to become prostrate.  Can flower within 35 days of sowing.  Flowering is negatively correlated with latitude and positively with rainfall , and is completely inhibited when night temperatures fall below 10ºC.

Defoliation

Management should be based on the fact that S. humilis is an annual with low tolerance of reduced light.
1. End-of-season management must favour seed set.  Heavy grazing late in the season reduces seed production.
2. Seedlings must be given an opportunity to develop with adequate light and exposed soil.  Heavy grazing in the early wet season, reduces the vigour of the perennial grasses, and allows the legume to develop.
3. Mature plants should not be shaded by taller grasses.  In swards the growth habit is strongly erect but the sward may become prostrate with very heavy grazing pressure.  Plants naturally become more prostrate with decreasing daylength below about 10 hours.

Fire

Top

Plants are killed by fire, although fire is mostly only an issue during the dry season after plants have completed their life cycle.  Fire helps to soften hard seed thus stimulating germination.  Burning of pastures should take place before the break of season, as fire-susceptible seedlings will be present after the early rains.

Agronomy

Establishment

Fresh seed can have >90% embryo dormancy, which lasts about 4 months.  It also has up to 100% hard seed, which, under natural conditions, is softened by fire or soil surface temperatures >50ºC.  Seed does not soften during normal storage.  Germination of commercial seed can be improved by mechanical scarification, hot water (80ºC for 10-15 minutes, then cool and dry), or one of the various dry heat treatments (85ºC for 1-2 hours, or heated for 15-20 seconds at 155ºC in a rotating drum, in each case cooling rapidly to ambient temperature ).  Sown just before the rainy season at 2-3 kg/ha.  Hulled or de-hooked seed gives freer flow through machinery.  S. humilis is fairly promiscuous in its rhizobial requirements, but seed can be inoculated with CB 82, CB 756 Bradyrhizobium, or their equivalents, to ensure best results.  Establishes best on a well-prepared seedbed (essential on heavy clays), but can also be sown into heavily grazed pasture or into the ash following a fire.  While the latter is less expensive, it is also much slower and may take up to 3 years to obtain good cover.  Seedlings are only moderately vigorous, but rapid root development provides tolerance of dry, and favours competition with associated species.

Fertiliser

One of the most efficient of the tropical legumes in extracting its calcium and phosphorus from the soil.  Grows in soil with available phosphorus levels as low as 3-10 ppm .  Although establishes in most soils without P, performs better with 20 kg/ha P at planting, with an occasional follow-up dressing.  Tolerant of high manganese and aluminium.

Compatibility (with other species)

Grows well with other species provided sufficient access to light.  Shaded out by taller grasses and significant tree canopy .

Companion species

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Pests and diseases

Commonly susceptible to anthracnose disease caused by type A Colletotrichum gloeosporioides and C. dematium, although resistant strains have been identified, e.g. 'Khon Kaen'.  Naturalised S. humilis in Australia was all but destroyed by anthracnose following appearance of the disease about 1973, although stands still persist in the seasonally dry north of the country.  Other diseases recorded are blight caused by Corticium solani, Sclerotium rolfsii, and bacterial wilt caused by Pseudomonas solanacearum.  Root knot nematode (Meloidogyne javanica) and burrowing nematode (Radopholus similis) attack S. humilis , but rarely cause losses.

Ability to spread

Readily spread by virtue of hooked seed adhering to livestock, seed being ingested and passing through livestock, and water movement.

Weed potential

Although widespread, rarely considered a significant weed.

Feeding value

Nutritive value

Top

CP level from 10-18%, and P levels from 0.04-0.20%.  IVDMD of young material of the order of 60-70% declining to 40% with age.

Palatability/acceptability

Relatively less palatable than associated grass in the young stage, but assumes increasingly high proportions in the animal diet as pasture matures.  Cattle raised on S. humilis , and familiar with it, will graze it when green.  The seed, which is about 60% digestible, improves forage quality.

Toxicity

No record of toxicity.

Production potential

Dry matter

Dry matter yields range from as little as 1 t/ha to a high of 7 t/ha, depending on soil and climatic conditions.  Yields are depressed by the presence of taller grasses.

Animal production

Top

Can support up to 2.5 beasts/ha, although 0.5-1 beasts/ha is more realistic, increasing carrying capacity of unimproved pasture considerably. Average liveweight gain of 0.3-0.5 kg/hd/day achievable.

Genetics/breeding

Largely self-pollinating;  2n = 20.  Colchicine induced tetraploids have been produced.  S. humilis has been identified as the probable maternal parent of both S. sympodialis and the allotetraploid , S. hamata sensu lato.

Seed production

Average yield, about 330 kg/ha but yields up to 1,100 kg/ha have been obtained under good conditions.  Frosts limit the options for seed production in the subtropics.

Herbicide effects

Tolerates 2,4-D at 125 and 250 g a.i./ha.

Strengths

  • Adapted to low fertility soils.
  • Tolerates high soil manganese and aluminium.
  • Free-seeding, self-regenerating.
  • Tolerates heavy grazing.

Limitations

Top

  • Susceptibility to anthracnose disease.
  • Low to moderate production.
  • Intolerant of shade.
  • Hooked seed difficult to sow.

Other comments

S. humilis was present in dense populations in the tropics and subtropics of northern Australia until the inadvertent introduction of anthracnose disease in 1973.  There are still vestigial populations in some areas, significant in some seasons, but markedly reduced compared with the pre-disease peak.

Selected references

Bogdan, A.V. (1977) Tropical Pasture and Fodder Plants. (Longman: London and New York).
Edye, L.A. and Topark-Ngarm, A. (1992) Stylosanthes humilis Kunth. In: 't Mannetje, L. and Jones, R.M. (eds) Plant Resources of South-East Asia No. 4. Forages . pp. 216-218. (Pudoc Scientific Publishers, Wageningen, the Netherlands).
Stace, H.M. and Edye, L.A. (eds) (1984) The biology and agronomy of Stylosanthes . (Academic Press: Sydney, Australia).

Internet links

Cultivars

Cultivars

Country/date released

Details

'Gordon' Australia (1968) Erect type, selected from naturalised population in Northern Territory for late flowering and good production compared with prostrate types.  Adapted to tropical areas with an annual rainfall of 1,130 mm or more, and with a marked dry season.  Succumbed to anthracnose.
'Khon Kaen'
(CPI 61674)
Thailand (1984) Institutional collection from Venezuela.  Low growing, prostrate type, with unrestricted height of 30-40 cm.  Less productive but more persistent than S. hamata 'Verano' (yield about half that of 'Verano'), but still capable of up to 7 t/ha DM.  Resistant to anthracnose and tolerant of heavy grazing.
'Lawson' Australia (1968) Erect type, selected from naturalised population in north Queensland for mid-season flowering and good production compared with prostrate types. Adapted to tropical and subtropical areas with an annual rainfall of 890-1,130 mm, and a long dry season.  First flowers mid-March extending over 8-10 weeks.  Succumbed to anthracnose.
'Paterson' Australia (1969) Erect type, selected for early flowering and good production compared with prostrate types.  Distinguished from 'Lawson' and 'Gordon' by its purplish black seeds (versus brown seed for other two cultivars).  Immature seeds are brown or brown with purple mottling.  Succumbed to anthracnose.

Promising accessions

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Promising accessions

Country

Details

None reported.