This species, the range of which is strictly African, has in the past been confused with the Asian species Aeschynomene aspera L.[].

Common Name:

General Information

Aeschynomene afraspera is an annual to perennial plant that can grow 1 - 3 metres tall with stems that can become somewhat woody and persist[]. Plants growing in isolation are sub-erect to spreading, with abundant branching; when growing in a dense stand they are erect with a single stem. The root and thick stem can be hollow or filled with pith[].
The plant is harvested from the wild for local use as a medicine and source of materials. It is being increasingly grown as a green manure crop in rice paddies.
Aeschynomene afraspera is widespread with an assumed stable population and no major widespread threats. The plant is classified as 'Least Concern' in the IUCN Red List of Threatened Species(2018)[].

Known Hazards

None known

Botanical References

Range

Africa - originally sub-Saharan from Senegal to Sudan, now widespread in the tropical lowlands.

Habitat

A semi-aquatic pioneer plant of marshes and temporarily wet places; at elevations up to 1,050 metres[, ]. It can form dense stands in soil depressions that are waterlogged during the rainy season, and in coastal freshwater lakes and rivers[].

Properties

Conservation Status	Least Concern
Medicinal Rating
Other Uses Rating
Habit	Annual/Perennial
Height	2.00 m
Growth Rate	Fast
Pollinators	Insects
Cultivation Status	Cultivated, Wild

Cultivation Details

Aeschynomene afraspera is found at elevations from sea level to 900 metres in tropical areas with a distinct dry season and a monomodal rainfall distribution[].
Succeeds in a wide range of soils, from pure dune sands along rivers to peat soils in mangrove swamps so long as there is sufficient plant-available phosphorus (at least 10 ppm). Soil reaction can range from alkaline in salt flats to highly acidic in acid sulphate soils[].
The plant occasionally appears as a weed in rice fields[].
A fast-growing plant, though initial growth until the fifth leaf has been produced is slow[]. With the onset of stem nodulation and/or closure of the canopy the plant then grows rapidly, and can reach a height of 60 - 150cm within 2 months[].
In the Philippines the plant starts flowering 65 days after sowing during the short-day season, and after 80 days when daylength exceeds 12 hours. With prolonged soil flooding, the otherwise short flowering period can extend to over 2 months[].
Fruit ripening causes drying and brown discolouration of leaves and stems, ending the growth cycle[].
An 8-week-old crop grown in a pure stand can accumulate a dry biomass of 4 - 6 tonnes per hectare, with a corresponding nitrogen yield of 80 - 200 kilos, provided sufficient water and soil P are available; 70% or more of this may be the result of biological nitrogen-fixation. As an intercrop, 35 - 60 kilos of nitrogen per hectare can be accumulated[].
Reported increases in rice grain yield due to the incorporation of a 6 - 8-week-old green manure range from 0.8 - 3.2 tonnes per hectare[]
This species has a symbiotic relationship with certain soil bacteria; these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby[].
The most distinctive characteristic of Aeschynomene afraspera is the presence of nitrogen-fixing nodules, not only on the roots but also on predetermined, sub-epidermal primordia of adventitious roots on stems and branches. Upon infection with rhizobia via rain splash or insect activity the root primordia can develop into nitrogen-fixing nodules. Since root nodules are scarce under anaerobic conditions in flooded soils, the plant has to rely on stem nodules to fix atmospheric nitrogen. Root primordia on stems become visible in 2-week-old plants, and profuse stem nodulation is apparent 3 - 5 weeks after germination. Up to 400 nodules can be found on the stem of a 2-month-old plant and 70 - 80% of the nitrogen in the biomass is reportedly derived from biological nitrogen fixation, indicating the high efficiency of the symbiosis in stem nodules[].

Edible Uses

None known

Medicinal

The pith of the stems is astringent and is applied to stop bleeding[].

Agroforestry Uses:

The potential use of this species as a fast-growing nitrogen source for wet-rice fields has only recently been noted. Since the late 1980s it has been widely used as a pre-rice green manure crop on experimental stations and in extension demonstration trials. So far it is only occasionally used by farmers in South and South-East Asia[].
The ability of the plant to form above-ground nodules and to fix nitrogen in waterlogged and marginal soils largely determines its value as a green manure in wet rice[].
Due to its soft structure, the green manure is easily incorporated into the soil and mineralizes rapidly even under flooded conditions. After 6 - 8 weeks of growth it is ploughed into the soil and the rice is transplanted 1 - 7 days later[].
In eastern India it is sometimes sown as an intercrop between rows of rice and trampled into the soil before it starts shading the rice[].
Relay planting has been used successfully to exploit the short fallow period between two rice crops in multiple cropping systems[].

Other Uses

The pith of the stems is used as insulation material[].
The stems are bouyant and are commonly made into floats[].

The stem can be used for fuel and, when soaked with oil, it can be used as a torch[, ].

Propagation

Seed - it has a hard seedcoat and may benefit from scarification before sowing in order to speed up and improve germination. This can usually be done by pouring a small amount of nearly boiling water on the seeds (being careful not to cook them!) and then soaking them for 12 - 24 hours in warm water. By this time they should have imbibed moisture and swollen - if they have not, then carefully make a nick in the seedcoat (being careful not to damage the embryo) and soak for a further 12 hours before sowing[].
Seeds require high soil moisture or flooded conditions for germination, but more than 2cm of standing water prevents seedling growth[].
Vegetative propagation is possible using stem cuttings with root primordia. Cuttings 15 - 20cm long from the basal stem show the highest survival rate and best growth.
Vegetative propagation may not be economic for green manure purposes, and is mostly used to establish seed production plants[].

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