Common names
American joint vetch (United States and Australia), thornless mimosa (Sri Lanka),
bastard sensitive plant (Jamaica), pega pega, pega ropa, antejuela, ronte, cujicillo,
dormilonga and others (Latin America) (Rudd, 1955).
Description
An erect-ascending, annual or short-lived perennial, shrub-like legume, 1 to 2 m tall.
Stems hairless, often hard but pithy in the lower regions; upper sections hairy, usually
glandular. Leaves 3 to 7 cm long. Leaflets 8 to 38 pairs, 5 to 15 mm long, 1 to 2 mm wide,
linear or linear to oblong, sensitive, folding together when touched. Stipules persistent,
linear-lanceolate, 1 to 2 cm long. Inflorescence a loose, few-flowered raceme, often
branched. Calyx about 4 mm long, deeply two-lipped. Corolla varying in colour from white
tinged with mauve or light violet to purple to flesh coloured, sometimes pinkish orange, 6
to 10 mm long. Pod usually slightly curved, four to eight jointed, up to 4 cm long, the
upper margin entire, the lower deeply indented at each segment joint; each segment
one-seeded; semi-circular, about 4 mm long. Seeds grey-green to dark and light brown.
Distribution
Native to Central America and tropical South America, extending as far south as
Argentina and north to Florida, United States, and the West Indies. Var. flabellata is
found mainly in wet or moist places at elevations up to 2 800 m. Used in Indonesia for
green manure and in Florida and Queensland, Australia, for forage.
Rudd (1955) identified three varieties: var. americana, found predominantly in the
Caribbean and adjacent areas; var. glandulosa (Poir.) Rudd, native to Central America and
tropical and subtropical South America; and var. flabellata Rudd, from Central Mexico.
Season of growth
Germinates in the first spring storms and grows through summer. Flowers and matures
from autumn till early winter.
Frost tolerance and regrowth after
frosting
None.
Altitude range
Sea level to 1 000 m in Jamaica (Adams, 1972).
Rainfall requirements
Essentially a wetland plant, requiring a minimum of 1 000 mm mean annual rainfall.
Drought tolerance
Slight.
Tolerance of flooding
Excellent. Its main natural habitats are low-lying wet areas and drainage ditches. A.
indica is probably better adapted to very wet sites and longer periods of flooding.
Soil requirements
Quite widely adapted, but particularly suited to wet, low-lying, sandy soils and to
similarly located solodics of coastal lowland country.
Rhizobium relationships
Promiscuous and nodulates readily with broad-spectrum cowpea-type inoculants.
Ability to spread naturally
Seed is widely distributed by cattle, both on their coats and in dung. Spread is rapid
and effective, generally with no rhizobial limitations, particularly in suitable wet
habitats.
Land preparation for establishment
The better the seed bed the better the establishment, but it has been satisfactorily
established into existing pastures in the Mackay region of central Queensland, with a
simple renovation and subsequent broadcasting of seed. In subsequent years, regeneration
occurs without further soil disturbance.
Sowing methods
Seed in pod or dehulled seed can be drilled into fully prepared seed beds or introduced
into existing sown or native pastures using strip cultivation and planting methods.
Herbicidal treatments and sod-seeding can also be used.
Sowing depth and cover
Hodges et al. (1982) recommend planting no deeper than 2.5 cm since seedling emergence
is reduced at greater depths.
Sowing time and rate
Planting is best done at the onset of the wet season (from June 1 to July 1 in central
Florida) (Hodges et al., 1982). Initial season production is reduced from later plantings.
The recommended planting rate in Florida is 5 kg./ha of dehulled seed or 12 kg./ha of seed
in pods (Hodges et al., 1982).
Number of seeds per kg.
For cv. Glenn, 368 000.
Percentage of hard seed
Seed in pod can be greater than 90 percent hard or as little as 55 percent, while the
mere act of dehulling samples can reduce the hard-seed level to 20 percent or less. If
necessary, further scarification can be applied.
Seed treatment before planting
Generally, dehulling of the seed is sufficient, but if the sample already has an
adequately low hard-seed content and seed is readily available, an increase in the sowing
rate to that for seed in pods is all that is required.
Nutrient requirements
On phosphate deficient soils, American joint vetch responds strongly to applied
phosphate. At Mackay, on soils with only 3 to 6 ppm available P, applications of 20 kg./ha
of P have given two- to fourfold increases in dry-matter yield (H.G. Bishop, personal
communication).
Response to lime at 2.24 tonnes/ha ground limestone was clear on very acid soils at Ona,
Florida, but responses to P and K have been variable on deficient soils (Hodges et al.,
1982). American joint vetch at least will grow on low-phosphorus soils. Liming should be
aimed at adjusting the pH to the range 5.5 to 6.0 (Hodges et al., 1982).
Compatibility with grasses and other
legumes
In the seedling regeneration phase at the beginning of each growing season, joint vetch
can be susceptible to competition from more vigorous grasses. Once established, the tall
and erect growing plants can stand competition. There are few legumes adapted to the wet
locations, so these rarely worry American joint vetch. The same remark applies to weeds.
Tolerance to herbicides
In seed-production stands, American joint vetch is tolerant to both trifluralin and
2,4-D (J.M. Hopkinson, personal communication).
Seedling vigour
In Florida, initial growth is slow. Plants require 60-70 days to reach a height of 60
cm and need special care at this stage. In existing stands the area should be heavily
grazed over winter, after seed set is complete, but grazing should cease when seedlings
reach a height of 5 cm, and not recommence until they are 45 cm tall (Hodges et al.,
1982).
Vigour of growth and growth rhythm
Once seedlings are established, growth is vigorous and difficult to control. It
continues until full flowering is achieved. Once maturity commences, growth ceases. After
frosting, residues rapidly break down.
Nitrogen-fixing ability
It is estimated in Florida that the equivalent of 112 kg./ ha N are added each year to
the pasture system by American joint vetch (Hodges et al.., 1982).
Response to defoliation
American joint vetch withstands heavy grazing well; under these conditions it branches
readily close to the ground and develops a low, dense, leafy canopy.
Grazing management
The only stage when special attention to grazing management is required is during
seedling establishment. In Australia, continuous grazing is then practised on most
pastures and American joint vetch accepts this well. In Florida, with rotational grazing,
a 3- to 5-week regrowth period between grazings is recommended for maximum production
(Hodges et al.., 1982).
Response to fire
Fire during the growing season is unlikely and a fire during the late dry season is
most likely to increase the germination of the hard seed, at the same time reducing
competition for the establishing seedlings.
Breeding system
Uncertain, but believed to be essentially cleistogamic, pollination taking place before
the flowers open.
Dry-matter and green-matter yields
In Malawi, a Rhodes grass/A. americana mixture yielded more than a Rhodes
grass/Neonotonia wightii mixture. A. americana, however, was less palatable than glycine:
only 65 percent of the herbage was consumed by animals, compared with 74 percent for the
glycine (Papua New Guinea, 1961). Parbery (1967a) obtained a maximum dry-matter yield of
13 325 kg./ha on Cunnunurra clay in 220 days. Applied nitrogen depressed the yield but
increased the protein percentage from 9.4 to 13.4 percent. The plant was 1 m high at
maturity and woody at the base. In Sri Lanka, five cuttings, each two months apart,
yielded 26.4 tonnes/ha of green material (Paul, 1951).
Suitability for hay and silage
It has been used for green chop, silage and hay making in Florida, but the high
moisture and mucilaginous nature of the green material make it difficult to handle, while
the hay dries brittle and twiggy. As a result, it is not ideal for these uses (Hodges et
al., 1982).
Value as a standover or deferred feed
Slight, as it becomes dry and brittle once mature, especially after frosting, and
disintegrates readily.
Feeding value
The mature pods contained 19.6 percent protein at Cunnunurra, north-west Australia
(Parbery, 1967a), while, when grown in dense stands at Peradeniya, Sri Lanka, hay had an
analysis of 12.72 percent moisture, 21.27 percent crude protein, 7.7 percent ash and 22.5
percent crude fibre (Paul, 1951). In Florida, stands of American joint vetch cut to 13 cm
stubbles when 30 cm tall, over two years averaged 17.5 percent crude protein and 70
percent in vitro organic matter digestion. Crops allowed to grow to 90 cm before cutting
gave poor-quality forage (Hodges et al., 1982).
Toxicity
None recorded.
Seed harvesting methods
Seed is readily harvested with a conventional wheat header. Crops need to be sprayed
with insecticide at flowering to control pod-boring insects. Seed crops in northern
Queensland are invariably attacked by powdery mildew late in the season, but this does not
appear to cause any trouble (J.M. Hopkinson, personal communication).
Seed yield
Yields of seed in pod as high as 2 tonnes/ha have been obtained from small plots in
Queensland (J.M. Hopkinson, personal communication).
Cultivars
An unnamed cultivar under the common name American joint vetch has come into use in
Florida in recent years. This comes from material tested in the early 1950s. Unnamed
material has also been used as a green manure crop in Indonesia (Whyte, Nilsson-Leissner
and Trumble, 1953) while it was studied as a forage and soil cover in Sri Lanka (Paul,
1951).
In 1983, cv. Glenn was released in Queensland for use on the wet coastal lowlands around
Mackay. 'Glenn' derives from seed collected in 1971 some 45 km south of Tampico, Mexico,
at an altitude of 15 m and a similar latitude (22° N) and rainfall (1 000 mm/year) to
Mackay. It is very similar to the Florida common material, maturing by mid-season, with
mature seed present by mid-May. One earlier-flowering and numerous later-flowering
accessions were present in the Mackay collection (H.G. Bishop, personal communication).
Diseases
The only disease noted to date has been powdery mildew on ungrazed seed crops.
Main attributes
Ability to thrive on low-lying, wet, rather infertile soils is its outstanding feature.
Main deficiencies
Lack of carryover forage for dry season use.
Performance
Cattle readily graze A. americana, and weight gains of 0.54 kg./ head/day have been
recorded over an 85-day period (Hodges et al., 1982), while gains of 0.51 kg./head/day for
177 days (December 5 to June 20) were recorded at Mackay (H.G. Bishop, personal
communication). In the latter case, the area was stocked at 2 steers per 1.25 ha.
Main reference
Hodges et al. (1982).
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