Stylosanthes seabrana


Scientific name

Stylosanthes seabrana B.L. Maass & 't Mannetje

Synonyms

Stylosanthes sp. aff. S. scabra
Stylosanthes sp. nov. aff. S. scabra

Family/tribe

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

Common names

caatinga stylo, aff. scabra.

Morphological description

Perennial (plants living 2-4 years) with woody base;  younger stems pilose on one side, viscid bristles (>1 mm) near the nodes.  Stipules pilose, very bristly, long lateral bristles present on stipule teeth, but rarely with a terminal bristle;  if so, very short.  Leaflets lanceolate to elliptic acute, upper surface glabrous, lower surface glabrescent, except for long often viscid bristles on the midrib below and on the margins;  veins raised, prominent below, whitish.  Inflorescence small capitate spike, yellow papilionaceous flowers with standard.  2-segmented pod, both segments usually fertile;  the upper segment 4-5 mm long (including recurved beak or hook 1-2 mm long), and the lower segment 2-3 mm long, densely pilose.  Seed asymmetrically reniform, 1.5 mm long, cream-coloured.  450,000 seed-in-pod and 690,000 dehulled seeds/kg.
Differs from S. scabra in having narrower, hairless leaflets, lateral bristles on the stipule horn, cream seed colour, lanceolate leaflets and being very early flowering.  It is intermediate in appearance between S. scabra cv. Seca and S. hamata cvv. Verano, Amiga.

Distribution

Native to:
Natural distribution restricted to between 9 and 14ºS and 40 and 46ºW in Bahia State, Brazil.

Uses/applications

For use as grazed pasture legume and summer ley legume on heavier textured soils where S. scabra and S. hamata do not grow well.  Extends the range of stylos into the frost-prone sub-tropics.

Ecology

Soil requirements

Occurs mainly on medium to heavy textured red or yellow earths in caatinga vegetation (variable deciduous forest and thorny thicket in the interior of north eastern Brazil, growing in an area of erratic rainfall and, in places, arid conditions).  Adapted to a wide range of soil types, particularly heavy clays, but also clay -loams, loams and sandy-earths, but not sands.  Prefers more fertile soils, but can accommodate soils that are fairly low in phosphorus and calcium and is often found at the same sites as S. scabra in its natural distribution.

Moisture

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Collected in areas with annual rainfall from 400-1,190 mm and a 2-7 month dry season.  Well-adapted to tropical and subtropical environments with summer-dominant rainfall between 500-1,000 mm.  Best performance in years with a long growing season.  Very drought tolerant but does not grow in seasonally flooded soils.

Temperature

Occurs from 9.9-14.2°S in situations, 400-1,050 m asl.  Although a tropical legume , it is much more frost tolerant than either S. scabra or S. hamata , withstanding night frosts down to -8 °C by developing crowns below the soil surface.  Does not grow in cool temperatures and drops leaves in winter, although basal stems can remain green if moisture is available and frosts are not severe.  Plants that are frosted to ground level regrow when moisture and temperature conditions are suitable in spring.  Seedlings may die during heatwaves in early summer.  The cultivars have succeeded in cultivation to at least 27º latitude (300 m asl ).

Light

No information available.

Reproductive development

In the southern hemisphere tropics, both cultivars began flowering in early February after sowing in December, with peak flowering in March and April, and large numbers of mature pods present from early May, with 'Primar' more advanced than 'Unica'.  'Primar' flowers 2-4 weeks earlier than 'Unica' in the establishment year, and can be harvested early July and 'Unica' in late July.  Appears to flower and set seed through much of the growing season in subsequent years.

Defoliation

Seeds well, developing a large bank of soil seed, with seed lasting in the soil for 2 or more years.  Seedling cohorts appear with each rainfall event during the warm season.  Management needs to favour development of occasional seedling cohorts to ensure maintenance of legume component.  Best achieved by reducing shading effect of taller grasses, being careful not to cause permanent damage to the grass since S. seabrana , once established, is more tolerant of heavy grazing than many associated grasses.  Heavy grazing early in the growing season favours the stylo, while light grazing or spelling at this stage favours the grass component.

Fire

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No information available.

Agronomy

Establishment

Can have high levels of hard seed (>70%) but usually hard seed levels are much lower than other stylos such as S. scabra and S. hamata .  Nevertheless it may be necessary to scarify seed to achieve 50% germination.  Highly specific inoculum requirement, not nodulating effectively with native strains of rhizobia.  CB 3481 strain Bradyrhizobium is used in Australia.  Poor nodulation may not be evident initially on fertile soils, as the legume utilises nitrogen mineralised during land preparation.  Nitrogen deficiency symptoms, including poor growth, yellowing of older leaves, and poor seed set, develop as available soil nitrogen declines, if the correct Bradyrhizobium strain is not present.  The effective strain can be introduced by inoculating seed in a preceding winter crop such as wheat, prior to sowing uninoculated S. seabrana .
Early sowing is recommended to give sufficient time for larger plants to develop and more seed to mature in preparation for the initial dry season or winter.  The small, dehulled seeds should be planted at 1-3 kg/ha (up to 6 kg/ha in hull), on the surface or no deeper than 1 cm.  Best sown into a well-cultivated, fallowed seedbed with good subsoil moisture and weed control.  Young seedlings compete poorly with established grasses or vigorous weeds in old cultivation, and sometimes fail when soil moisture is marginal or heat wave conditions occur.  Establishment and growth can be slow in the first two years.

Fertiliser

Application of 10-20 kg/ha P at planting and every 2 or 3 years after establishment (to maintain available soil P levels at ±8 ppm (mg/kg) improves both plant and animal performance.  Molybdenum and sulphur may also be necessary in some situations.

Compatibility (with other species)

Forms good associations with grasses adapted to clay and clay loam soils under rotational and continuous grazing systems.  Competes effectively with, and can suppress weeds such as Heliotropium amplexicaule, a major problem in cultivation on lighter soils.

Companion species

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Pests and diseases

High levels of resistance to anthracnose, Colletotrichum gloeosporioides.  May require treatment with benomyl if anthracnose develops in seed crops grown in humid environment.  No other major problems.  Botrytis flower blight caused by Botrytis cinerea, does occur but is not severe.  The phytoplasma disease that severely affects seed crops of S. scabra has not been a problem in S. seabrana .

Ability to spread

Initially constrained by lack of appropriate rhizobium, but establishes readily once effective inoculum is present.

Weed potential

High seed production and relatively high levels of hard seed suggest the species may have some potential weediness once an effective rhizobium strain spreads, although there is no evidence that this has occurred.

Feeding value

Nutritive value

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For one sample of 'Unica', 23% CP, 0.22% P and 22% ADF in the leaf, 11% CP, 0.17% P, and 38% ADF in the stem of the terminal 15 cm of shoots.  Leaf constituted about 54% of the sample.

Palatability/acceptability

Moderate palatability - generally only lightly grazed, stock preferring the associated green grass leaf.  The main contribution is to improve the quality of associated grass and provide higher quality feed as grasses mature in grazing situations and in improving soil fertility for succeeding crops.

Toxicity

None recorded.

Production potential

Dry matter

In good growing conditions and in pure swards, can produce over 4 t/ha DM during the growing season .  DM yields often higher than those of S. scabra .

Animal production

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0.6 kg/hd/day LWG for 10 months of the year from steers grazing a mixed S. seabrana /Panicum coloratum /native grass pasture, equating to over 100 kg/ha/yr LWG for this period.  Can give 80-85% increase in cattle performance over that from unimproved pasture .

Genetics/breeding

Diploid 2n = 20;  possible progenitor, along with the diploid , S. viscosa , of the allotetraploid , S. scabra .

Seed production

Mature pods from May onwards, with 'Primar' more advanced than 'Unica'.  May need to use fertiliser N to compensate for slow nodulation.  'Primar' harvested early July and 'Unica' in late July.  Seed holds well in head.  Single pass with mechanical harvester can produce about 700 kg/ha of good quality seed in hull with no nitrogen applied, and up to 1,000 kg/ha, particularly if N is applied.

Herbicide effects

Susceptible to 2,4-D at the seedling stage, but moderately tolerant when mature, with only temporary curling of plants.  May also be susceptible to trifluralin, but is tolerant of imazethapyr, which is used in seed crops for pre-emergent grass control.

Strengths

  • Suitable for clay and clay loam soils.
  • More cold-tolerant than S. scabra or S. hamata .
  • Early flowering, and prolific seeding.
  • Tolerant of heavy grazing.
  • Anthracnose resistant.

Limitations

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  • Drops leaf in cool/dry season.
  • Highly specific rhizobium requirement.

Other comments

  

Selected references

Edye, L.A. and Maass, Brigitte L. (1997) Recent advances in studies of anthracnose of Stylosanthes. I. The biogeography of Stylosanthes hamata , S. scabra and "Stylosanthes seabrana ".  Tropical Grasslands, 31, 417-423.
Hall, T.J. and Glatzle, A (2004) Cattle production from Stylosanthes pastures. In Chakraborty, S. (ed.) High yielding anthracnose-resistant Stylosanthes for agricultural systems. ACIAR Monograph No. 111 .
Maass, B.L. and 't Mannetje, L. (2002) Stylosanthes seabrana (Leguminosae: Papilionoideae), a new species from Bahia, Brazil. Novon, 12, 497-500.
Pengelly, B.C., Clem, R.L. and Whitbread, A.M. (2004) The role of Stylosanthes spp. in mixed crop-livestock systems in Africa and Australia. In Chakraborty, S. (ed.) High yielding anthracnose-resistant Stylosanthes for agricultural systems. ACIAR Monograph No. 111 .

Internet links

Cultivars

Cultivars

Country/date released

Details

'Primar'
(CPI 92838B)
Australia (1996) Origin unknown - contaminant in seedlot.  Ascendant habit, dome shaped to 40-50 cm (erect to 1 m in vigorous, dense stand), with profuse branching.  Reddish stems and inflorescence , especially in mature plants.  Earlier flowering and more cool tolerant than 'Unica'.  Selected for application in the subtropics.  Minor anthracnose in the tropics.
'Unica'
(CPI 110361, CIAT 10033)
Australia (1996) From Bahia, Brazil (12.33ºS, 41.06ºW, 470 m asl, rainfall 960 mm).  Erect, vase-shaped growth habit to 40-50 cm (to 1 m in vigorous, dense stand) green stems.  Flowers 2-4 weeks later than 'Primar', especially in the establishment year.  Selected for use in more tropical environments.  Has been found to be persistent and productive under grazing in the sub-humid/semi-arid subtropics.  More anthracnose resistant than 'Primar'.

Promising accessions

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Promising accessions

Country

Details

CPI 104710 Australia From Bahia, Brazil (12.2ºS, 42.5ºW, 800 m asl, rainfall 680 mm).  Similar to 'Unica', vigorous growth, good seed yield, but lower leaf/stem ratio.