Desmanthus leptophyllus


Scientific name

Desmanthus leptophyllus Kunth

Turner (1950) regarded Desmanthus virgatus as an all-encompassing species, comprising D. virgatus , D. pubescens , D. pernambucanus , D. glandulosus and D. leptophyllus .  Despite taxonomic revision by Luckow (1993) that resolved the complex to distinct species, many authors continued to refer to all species as D. virgatus in the literature until the late 1990s.  Correct nomenclature is now generally used.

Synonyms

Acuan guadeloupense Britton & Rose
Acuan insulare Britton & Rose
Acuan latum Britton & Rose
Desmanthus insularis (Britton & Rose) Leon
Desmanthus latus (Britton & Rose) Standley
Desmanthus multiglandulosus Britton & Killip

Family/tribe

Family: Fabaceae (alt. Leguminosae) subfamily: Mimosoideae tribe: Mimoseae.  Also placed in: Mimosaceae.

Common names

desmanthus (Australia);  frijolillo (Brazil);  guashe chico, guashillo (Nicaragua);  malicia de bode (Peru) urpa micuna.

Morphological description

Small erect shrub to 3 m tall, woody at the base and generally strongly branched.  Young stems green and hairless, angular with golden corky ridges.  Older stems hairless, shiny red or brown.
Bipinnate leaf 4-11 cm long with 4-8 pairs of pinnae 16-39 mm long and 16-36 pairs of leaflets/pinnae 2-6 mm long and 0.5-1.0 mm wide.  Persistent stipules 3-10 mm long.
Small flowering heads (condensed spikes) 0.5-0.9 cm long, occur singly in leaf axils on short peduncles (to 2.7 cm long).  Heads contain 5-12 flowers that may be perfect, functionally male or sterile.  Sterile flowers occur rarely, when present 1-2 occur at the base of the head.  Male flowers occur towards the base of the head above the sterile flowers, but below the perfect flowers and number 0-7.  Perfect flowers occur apically and are 2.0-3.7 mm long.  Fruiting stalks 1.0-3.3 cm long bear 1-9 pods.
Pods are linear , 2.2-8.8 cm long and 2.5-4.0 mm wide, opening along both margins.  Reddish-brown to nearly black at maturity.
Seeds 9-27/pod, 2.1-2.9 x 1.4-2.7 mm, flattened and ovate in shape and reddish- or golden-brown in colour.

Distribution

Native to:
Natural distribution ranges from Veracruz and Chiapas in Mexico, south throughout Central America to Colombia, Venezuela, Ecuador, Peru, Chile and northern Brazil.
Occurs naturally in coastal thickets, roadsides and marshes on sandy, rocky limestone and saline soils at altitudes of sea level to 1,500 m.

Uses/applications

Grazed by herbivores in the native range.  Exotic component of improved permanent pastures in northern Australia, and protein banks and hedgerows in south-east Asia.  Has potential as a long-term (>3 years) phase legume in cropping systems.

Ecology

Soil requirements

Occurs on a wide range of soil types from coastal sands to rocky limestone and saline soils.  In exotic locations, Desmanthus spp. are generally selected for their persistence on heavy clays, including alkaline soils, but will grow productively on lighter soils of neutral to alkaline reaction.

Moisture

Top

Occurs naturally in more or less strongly seasonally wet environments with 1,000-2,000 mm annual rainfall.  Well-adapted to 550-1,000 mm average rainfall environments in exotic locations.

Temperature

Primarily a species of lowland, humid-tropical locations with average annual temperature ranging from 22-28°C and with only minor monthly fluctuations in temperature .  It is reasonably cold tolerant however, growing into the subtropics in exotic locations.  Although defoliated by heavy frosts, it will regrow from crowns once there is sufficient heat and moisture.

Light

Poor tolerance of medium to heavy shade.

Reproductive development

Flowering and fruiting occurs predominantly throughout autumn and to a lesser extent, in spring.

Defoliation

Tolerant of regular cutting and grazing by ruminants.

Fire

Top

Will regrow from the crown after moderate fire.  Fire can be useful in breaking seed dormancy.  Germination of accessions CPI 37143 and CPI 38581 was increased from <10% to 40-75% after being subjected to temperatures of 60-100°C.  Seed buried at 0.5-3.0 cm is subjected to these temperatures during grass fires.

Agronomy

Establishment

Sow 2 kg/ha of scarified seed at a depth of 0.5–2.0 cm into moist soil with at least 50–60 cm depth of good moist soil to ensure establishment.  Deeper planting depths may prevent or delay emergence.  Surface broadcasting onto a well-prepared seed-bed, followed by rolling, and planting using a “crocodile” seeder have also given good results.  D. leptophyllus has been sown successfully into cultivated strips, and sod-seeded into slashed pasture treated with glyphosate to suppress grass growth.
Fresh seed is extremely hard-seeded and should be scarified, either abrasively (eg. using a rice polisher) or by hot water treatment (4-10 seconds in boiling water), to raise the germination to a minimum of 50–70%.  It is important to achieve good establishment from the plant crop as seed produced from paddock plants will remain hard-seeded for 5–6 years.

Fertiliser

May respond to S, Mo, P, Cu and Mn on clay soils.  A critical leaf tissue concentration of 0.2% S is required for optimum productivity.  Highest DM yields at P-deficient sites were achieved with the addition of 50 kg/ha at Maharashtra, India, and 80 kg/ha P2O5 at Texas, USA.  Higher rates of P-fertiliser decreased DM yields at both sites.

Compatibility (with other species)

Its deep-rooted habit enables it to be grown with stoloniferous grasses.  In northern Australia, plant crops of cv. Bayamo generally persist strongly in buffel grass (Cenchrus ciliaris ) and other tropical grass pastures, but long term persistence is commonly poor in sub-tropical environments due to low seed production in the late-flowering cv. Bayamo and the extreme hardseededness of any seed that is produced.  Has formed productive mixtures in exotic, sown pastures, as well as with native species.

Companion species

Top

Grasses:  Buffel grass (Cenchrus ciliaris), Bambatsi panic (Panicum coloratum var. makarikariense), Queensland bluegrass (Dichanthium sericeum ).
Legumes:  Medicago sativa is sometimes sown with desmanthus/grass pastures in subtropical areas of southern Queensland.

Pests and diseases

Occasional, minor damage by psyllid insects (Accizia spp.) has been reported in northern Australia.  The psyllids cause more serious damage in seed crops.  Several seed-eating bruchid beetles (five Acanthoscelides spp. and one Stator sp.) are known to infest Desmanthus.  No other reports of serious pests and diseases were cited.

Ability to spread

Being late flowering and producing only limited seed, cv. Bayamo does not generally spread under grazing.  Early seeding cultivars capable of moderate to high seed production are required to ensure long-term persistence in grazed pastures.

Weed potential

Has potential to become a weed of disturbed areas in humid-tropical environments due to its high seed production and erect, woody habit , but is not currently listed as a major weed.  Unlikely to become weedy in sub-tropical environments due to poor seed set.

Feeding value

Nutritive value

Top

Evaluations generally do not distinguish between species of Desmanthus, and are based on cvs. Marc, Bayamo and Uman.  Crude protein content of the entire plant ranged from 10.5-15.5%, with leaves averaging 22.4% and stems 7.1%.  A study of 18 accessions grown in India reported an average CP content of 21% (range 15-27%), and average NDF and ADF contents were 42 and 35%, respectively.
In sacco digestibility of leaves of CPI 38351 was 51% after 48 hrs and 77% after 96 hrs.

 

Palatability/acceptability

Palatable to grazing ruminants and grazed by beef cattle throughout the growing seasonDesmanthus has been observed to be less palatable than leucaena (Leucaena leucocephala ) but more readily eaten than Stylosanthes scabra cv. Seca.  Accession CPI 38351 was similar to D. virgatus Q9153, being more palatable than other Desmanthus accessions.

Toxicity

No toxicities to ruminant livestock were reported in the literature.  Desmanthus spp. do not cause bloat in ruminants because they contain 2-3% (of total DM as tannic acid equivalent) condensed tannins.

Production potential

Dry matter

CPI 38351 was the highest yielding accession of 47 Desmanthus accessions grown at 8 sites in Queensland, Australia, out-yielding accessions of D. virgatus and D. pubescens .  All accessions of D. leptopyllus were high yielding in the evaluation producing DM yields of 2.4–3.9 t/ha/year.
‘Bayamo’ produced over 9 t/ha DM under irrigation in a sub-humid environment.
Presentation yields of D. leptophyllus CPI 38351 in grazed pastures in subtropical Australia ranged from 100–500 kg/ha DM during the first 5 years following planting and contributed between 3 and 13% of total DM yield.  Poor seed set limited persistence in this subtropical environment.
In permanent, grass-legume pastures, contribution to DM will be greatest on soils of moderate fertility in tropical, sub-humid environments where grass competition will be only moderate and D. leptophyllus will seed freely and recruit from seed.

Animal production

Top

In a pen feeding experiment where a Mitchell grass (Astrebla spp.) basal diet was supplemented with CPI 38351, DM intake of merino wethers increased from 580 to 742 g/head/day, and wool growth increased from 0.48 to 0.66 g/day/cm².
No grazing trials assessing animal liveweight gains from D. leptophyllus are reported in the literature.

Genetics/breeding

Taxonomic confusion within the genus has led to a vast range of accessions from D. pernambucanus , D. leptophyllus , D. pubescens and D. virgatus being evaluated as D. virgatus .  However, there is a wide range of genetic and morphological diversity within D. leptophyllus and many of those accessions have cultivar potential.  Evidence from small plot seed production suggests that the species is predominantly self-pollinating.
No breeding work has occurred to date.

Seed production

Seed yields of 500-600 kg/ha are achieved from direct-headed crops, but considerable seed losses occur due to uneven ripening and early seed fall.  The potential seed yield using a suction harvester is in excess of 1,000 kg/ha, however the suction required to collect the dense Desmanthus seed can result in large quantities of small stones in the sample.
Late-flowering types require an extended period of favourable moisture conditions to flower and set seed.  A high proportion of under-developed, immature embryos that are non-viable or of low vigour can occur in late-flowering types grown in sub-tropical environments were frosting and moisture stress may occur during seed development.  These seeds are of similar dimensions to fully mature seeds and are therefore very difficult to remove during conventional seed grading.
A psyllid insect (Accizia spp.) can cause severe damage to seed crops in Australia and may need to be controlled using insecticides.
In Jhansi, India, seed production was increased by adding 60 kg/ha P2O5.

Herbicide effects

Killed by Access® herbicide (120 g/L picloram and 240 g/L triclopyr).

Strengths

  • High DM productivity.
  • High seed production.
  • Tolerant of heavy grazing.
  • Persistent in low rainfall environments.
  • Has potential as a ley legume species due to high DM yields and late flowering.
  • Tolerant of alkaline, sodic, saline and heavy clay soils.

Limitations

Top

  • Establishment on heavy soils can be problematic because of small seeds.
  • Not suitable for short-term pastures (<3 years) because of establishment risks.
  • Highly specific in its rhizobium requirements (CB3126).

Other comments

Recruitment from seed in grass-legume pastures will not occur until hardseededness has been overcome by weathering.  In the absence of fire, this will require several seasons to occur.  Grass fires can soften seed of D. leptophyllus .  Success depends on the intensity of the fire and the depth of seed in the soil.

Selected references

Burt, R.L. (1993) Desmanthus: a tropical and subtropical forage legume . Part 1. General Review. Herbage Abstracts, 63, 401-413.
Clem, R.L. and Cook, B.G. (2004) Identification and development of forage species for long-term pasture leys for the southern speargrass region of Queensland. In: Whitbread, A.M. and Pengelly, B.C. (eds) Tropical legumes for sustainable farming systems in southern Africa and Australia. ACIAR Proceedings No115. pp. 64–79. (Australian Centre for International Agricultural Research, Canberra, Australia).
Gardiner C.P. and Burt R.L. (1995) Performance characteristics of Desmanthus virgatus in two contrasting tropical environments.Tropical Grasslands29, 183-187.
Hopkinson, J.M. and English, B.H. (2004) Germination and hardseededness in Desmanthus. Tropical Grasslands, 38, 1-16.
Jones, R.M., Bishop, H.G., Clem, R.L., Conway, M.J., Cook, B.G., Moore, K. and Pengelly, B.C. (2000) Measurements of nutritive value of a range of tropical legumes and their use in legume evaluation. Tropical Grasslands, 34, 78–90.
Jones, R.M. and Brandon, N.J. (1998) Persistence and productivity of eight accessions of Desmanthus virgatus under a range of grazing pressures in subtropical Queensland. Tropical Grasslands, 32, 145-152.
Luckow, M. (1993) Monograph of Desmanthus (Leguminosae-Mimosoideae). Systematic Botany Monographs. Vol. 38. The American Society of Plant Taxonomists.
Pengelly, B.C. and Liu, C.J. (2001) Genetic relationships and variation in the tropical mimosoid legume Desmanthus assessed by random amplified polymorphic DNA. Genetic Resources and Crop Evolution, 48, 91-99.
Spiers, P.R.., Brandon, N.J., Date, R.A., Bahnisch, L.M. and Gearge, D. (1998) Nutrient limitations of clay soils for Desmanthus virgatus II. A glasshouse study of 7 soils. Tropical Grasslands, 32, 6–12.

Internet links

Cultivars

Cultivars

Country/date released

Details

'Bayamo'
(CPI 82285)

Queensland, Australia A tall (100–150 cm), mid-season cultivar, flowering in 110 days.  Among the highest yielding of the Desmanthus accessions evaluated in southern and central Queensland.  Better suited to southern Texas than Desmanthus spp. cvv. Marc and Uman.

Promising accessions

Top

Promising accessions

Country

Details

CPI 38351 Queensland, Australia Tall, late-flowering accession from Venezuela.  Prolific early seed production, persistence and moderate productivity under heavy grazing during 6 dry years in northern Australia.  Also performed strongly in agronomic trials at 8 sites.
CPI 63453 and CPI 38820 Queensland, Australia High-yielding accessions selected for use as a ley legume for run-down cropping lands in central Queensland, Australia.  Produced very high seed yields (1.3-1.5 t/ha), although significant losses from direct heading are expected.
CPI 92806, CPI 92809 CPI 92818 and TQ 90 Queensland, Australia Persistent, high yielding accessions in small plot trials in Heteropogon contortus pastures in south-east Queensland.
AC10 and AC11 Queensland, Australia Accessions well adapted to clay soils in north Queensland.