Acacia nilotica


Scientific name

Acacia nilotica (L.) Delile

Subordinate taxa:
Acacia nilotica subsp. adstringens (Schumach. & Thonn.) Roberty
Acacia nilotica subsp. kraussiana (Benth.) Brenan
Acacia nilotica subsp. nilotica A. F. Hill

Some references also list Acacia nilotica subsp. tomentosa but this subspecies is not recognised by GRIN.

Synonyms

Acacia arabica (Lam.) Willd.
Acacia scorpioides W. Wight
Mimosa arabica Lam.
Mimosa nilotica L.
Mimosa scorpioides L.

Family/tribe

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

Common names

acacia gomifera, acacia de cayenne, acacia gomme, arabische gummiakazie, babul, babul acacia, black piquant, casha, cassie, egyptian acacia, goma arabica, gommier rouge, gum arabic tree, Indian gum-arabic-tree, gum arabic tree , thorn-mimosa, thorny acacia.

Morphological description

Perennial shrub or tree, 2.5–10 (–20) m tall, variable in many aspects. Branches spreading, forming a dense flat or rounded crown with dark to black coloured stems; branchlets purple-brown, shortly or densely pubescent , with lenticels. Bark thin, rough, fissured, deep red-brown.
Spines (thorns) thin, straight, light-grey in axillary pairs, usually in 3–12 pairs, 5–7.5 cm long in young trees, mature trees commonly without thorns. Leaves bipinnate 30–40 mm long, often with 1–2 petiolar glands and other glands between all or only the uppermost pinnae; pinnae 2–11 (–17) pairs, with 7–25 pairs of leaflets (1.5–7 mm long) per pinnae.  Peduncles clustered at nodes of leafy and leafless branchlets. Flowers prolific, golden yellow, in globulus heads 1.2–1.5 cm in diameter. Pods straight or slightly curved, 5–15 cm long on a pedicel, 0.5–1.2 cm wide, with constrictions between the seeds giving the appearance of a string of pearls, fleshy when young, indehiscent, becoming black and hard at maturity. Seeds deep blackish-brown, smooth, sub-circular, compressed, areole 6–7 mm long, 4.5–5 mm wide. Seed weight ranges from 5,000–16,000 seed/kg.

Subsp. nilotica is characterized by glabrous pods and twigs, or nearly so, while subsp. kraussiana has strongly constricted white-grey hairy pods. Pods lightly, or not constricted in subsp. adstringens .

Distribution

Native to:
Africa:  Algeria, Angola, Botswana, Egypt, Ethiopia, Gambia, Ghana, Guinea-Bissau, Kenya, Libya, Malawi, Mali, Mozambique, Niger, Nigeria, Senegal, Somalia, South Africa - Transvaal, Sudan, Tanzania, Togo, Uganda, Zambia, Zimbabwe.
Asia:
Arabian Peninsula:  Oman, Saudi Arabia, Yemen.
Western Asia:  Iran, Iraq, Israel, Syria.
Indian Subcontinent:  India, Nepal, Pakistan.

A. nilotica subsp. nilotica is restricted to well-drained seasonally flooded and riverine habitats from Senegal and northern Nigeria, to Sudan, Arabia and India.
A. nilotica subsp. kraussiana is the most common form in east tropical Africa including Botswana, Zambia, Rhodesia, Malawi, Tanzania, Angola, Mozambique, Transvaal, and Natal.
A. nilotica subsp. adstringens is the commonest variety in west Africa, from Senegal to Nigeria and widespread in northern parts of tropical Africa. Occurs in wooded grasslands, savannas and dry scrub forests above the flood plains.

Naturalised in:
Northern, sub-humid Australia where it is considered to be an invasive weed. Also naturalised in areas of eastern Indonesia.

Uses/applications

Drought forage, browse, foliage and seeds are eaten by a wide range of herbivores. Highly valued as fodder and fuelwood in regions of semi-arid Africa and India. Used as a pioneer species in land rehabilitation and as a barrier to desertification. The timber has been used to produce railway sleepers, fence-posts and fuel-wood. Non-forage/timber uses include gum/resin, tannin /dyestuff; traditional medicine and vertebrate poisons.

Ecology

Soil requirements

Tolerates a wide range of soil types, thriving in alluvial and heavy clay soils with pH 5.0–9.0. When used in land reclamation, A. nilotica can be planted onto degraded saline/alkaline soils with a soluble salt content below 3%.

Moisture

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Adapted to annual rainfall of 300–2,200 mm. Vigorous in seasonally flooded environments.

Temperature

Grows from 0–1,340 m altitude, with an annual mean temperature of 18–28°C. Tolerates extremes of temperature (-1–50°C) when established, but is frost sensitive as a seedling.

Light

Seedlings are shade intolerant.

Reproductive development

Flower initiation is triggered by declining temperature and possibly by declining soil moisture (generally throughout autumn); green pods form during the dry season and ripen into the late dry/early wet season.

Defoliation

Tolerant of regular grazing and defoliation . Protected from severe grazing by the presence of long thorns. Heavy grazing by goats (12 head/ha) can be used to control A. nilotica , although only a small percentage of trees will be killed.

Fire

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Tolerant of fire.

Agronomy

Establishment

Seed is hard-coated and must be scarified (mechanical abrasion, acid, or hot-water treatment) before planting. Can be established by direct seeding of scarified seeds or by transplanting of nursery-grown seedlings. Can be aerially seeded.

Fertiliser

No information available.

Compatibility (with other species)

Has formed thickets where the rate of utilisation is low. Stands of 25–30% tree canopy have reduced productivity of Mitchell grass (Astrebla spp.) in Australia by up to 50%.

Companion species

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Not generally planted in combination with other forage species. May be integrated as a hedgerow species or windbreak.

Pests and diseases

Affected by a wide range of pests and diseases across the native range. The stem borer Cerostema scabrator damages young plantations in India.  A number of bruchid beetles infest seed, destroying up to 70% of seed crops. A range of leaf-eating insects occasionally defoliate stands in India.
Fungal pathogens can also be damaging.

Ability to spread

Cattle eat the mature pods and at least 40% of seed remains viable after passing through the gut. Seed germinates readily in the dung. Viability of seed eaten by sheep and goats is much lower than for cattle because sheep and goats tend to chew the seed. Seed can also be transported by water.

Weed potential

Introduced into Myanmar, Iran, Vietnam, Indonesia, the Caribbean and Australia where it is spreading vigorously in many locations. Is classed as a “weed of national significance” in Australia, infesting over 7 million ha of rangelands in the arid and semi-arid tropics. With the exception of A. nilotica subsp. kraussiana in southern Africa, the tree is not known to be weedy in its native range because seed numbers are greatly reduced by a wide range of herbivores and insects.

Feeding value

Nutritive value

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Leaves contain 2.2–2.6% N, 16.9–20.0% NDF, 13.3–14.1% ADF, 7.2–8.7 MJ/kg energy, 10–21% crude fibre and 6–9% condensed tannins. Pod and seed contain 1.6–2.2% N, 10 MJ/kg energy, 12–18% crude fibre and 4–7% condensed tannins. Pods alone contain 2% N, 25% NDF, 17% ADF .
In digestibility trials conducted in Zimbabwe, of several species browse species tested, intake of A. nilotica was the lowest.

Palatability/acceptability

Leaves and pods are generally well accepted by small ruminants. Cattle require prior experience or an extended period of adaptation. Dried pods are relished by herbivores in the native range.

Toxicity

A. nilotica has been reported to contain l-arabinose, catechol, galactan, galactoaraban, galactose, N-acetyldjenkolic acid, N-acetyldjenkolic acid, sulphoxides pentosan, saponin and tannin .

Production potential

Dry matter

No reports of DM production were cited. Forage use is generally as a browse for sheep and goats, or as a drought relief feed.

Animal production

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Used as a protein supplement in semi-arid and sub-humid rangelands to increase the protein content of grasses during the dry season.
Replacing conventional concentrate feeds of both weaner kids and lambs with 25% mango seed kernels and 23% A. nilotica seeds reduced feed costs without affecting feed intake, nutrient utilization, growth rate, blood profile and carcass traits.
In Australia, A. nilotica is kept under control when grazed by sheep, goats and camels, whereas it continues to spread in paddocks grazed solely by cattle.

Genetics/breeding

Wide range of intraspecific diversity exists and agronomic assessments of provenances have been conducted. The taxa form a polyploid complex. Most are tetraploids including subsp. adstringens, (2n = 4x = 52); but higher numbers have been found in subsp. nilotica (2n = 8x = 104) and subsp. tomentosa 2n = 16x = 208).

Seed production

Flowers prolifically over an extended period, but only a very small proportion (0.1%) may form pods.  Seed production varies with provenance, but mature trees can produce up to 2–4 kg seed in a good fruiting season. Seed viability declines rapidly and 95% of seed may be dead after 2 years. However, a small percentage of seed will remain viable for up to 15 years.

Herbicide effects

Can be controlled by basal bark spray or cut stump application of common arboricides. Young plants can be controlled using an overall foliar spray. Soil-applied herbicides have also been successfully used.

Strengths

  • Can be established readily from seed.
  • Extremely drought tolerant.
  • Leaves and pods have high CP content.

Limitations

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  • Extremely invasive in exotic habitats.
  • Large spines reduce consumption of the foliage by ruminants.
  • Anti-nutritive compounds reduce forage quality.
  • Susceptible to a wide range of pests and diseases in native range.

Other comments

In the Sudan, timber trees are managed on a 15–20 year rotation, primarily for use as railway sleepers. The wood is heavy and durable and is used for heavy construction as well as tool handles and carts. Makes high quality charcoal and fuelwood.

Selected references

Carter, J.O. (1994) Acacia nilotica : A tree legume out of control. In: Gutteridge, R.C. and Shelton, H.M. (eds) Forage Tree Legumes in Tropical Agriculture. pp. 338–351. (CAB International, Wallingford, UK).
Fagg, C. (2001) Acacia nilotica : Pioneer for dry lands. In: Roshetko, JM (ed.) Agroforestry Species and Technologies. pp. 23–24. (Winrock International, Arizona, USA). 
Spies, P. and March, N. (2004) Prickly acacia – Approaches to the management of prickly acacia (Acacia nilotica ) in Australia. Department of Natural Resources, Mines and Energy, Queensland, Australia.

Internet links

Cultivars

Cultivars

Country/date released

Details

No cultivars have been officially released.      

Promising accessions

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Promising accessions

Country

Details

   Burkina Faso Provenances from Burkina Faso and Senegal had by far the best agronomic performance, compared with growth of provenances from India, which was very poor.