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Desmanthus virgatus (L.) Willd. |
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Leguminosae
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Author: Le Houérou
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Dwarf koa, desmanthus (Hawaii). Under-shrub or small shrub, 2 to 3 m tall, habit variable, nearly erect or (more commonly) diffuse or decumbent; branchlets glabrous. Looks like a dwarf non-thorny Acacia or Leucaena leucocephala but has slender, angular, pithy stems, smaller leaflets and narrow pods. Leaves moderately small, bipinnate; 10 to 20 leaflet pairs per pinna, petiole usually no more than 5 mm long. Inflorescence of axillary, pedunculate heads toward the tips of the twigs; head small, dense, few-flowered, the flowers all erect, whitish, sessile; pod linear, 4 to 6 cm long and 3 to 4 m wide, flat, glabrous, shortbeaked, dehiscent on both valves, seeds oblique. Under cutting treatments, Desmanthus developed a crown similar in many respects to that of alfalfa (lucerne). The size of the crown gradually increased with each successive crop until it was up to 15 cm across after three years. This well-developed, vigorous crown produced as many as 50 slender, erect stems, seldom branched, pithy in the centre, brittle and fairly soft. In its native and naturalized habitats Desmanthus tends to colonize open, disturbed land and environments such as roadsides, unused blocks of land, quarries etc. It does not occur in pastures in Hawaii. Grows best in hot weather; its frost tolerance is unknown. In Santiago, Cape Verde, it became invasive under 250 mm of MAR but it usually occurs under a rainfall regime of 1000 to 1500 mm. It is quite drought tolerant. Grows best in sandy and other open-textured soils. In Paraguay it occurs on clay soils. Its pH preference is from 5.0 to 6.5 (Fretes, Samudio and Gray, 1970). Native to the American tropics and sub-tropics, sometimes naturalized in African dry lands (e.g. Santiago, Cape Verde), Senegal, Zambia, South Africa. Found in Florida and Texas, United States, to Argentina; West Indies; Galapagos Islands; Hawaii. Found at elevations from sea level up to 300 m. Being deep rooted it stands competition from perennial grasses. However, stoloniferous grasses compete with it. It is highly palatabile and can be harvested four times a year in Hawaii, cutting it at the early pod stage. It flowers 45 to 50 days after cutting. In Hawaii, the plants were cut 5 to 7.5 cm above ground with a mower. Cutting at 91-day (four cuts per year) intervals gave the highest yield, 23.68 tonnes/ha/ year over three years; Leucaena leucocephala gave a significantly higher yield than desmanthus. The yield of oven-dry forage decreased in the second and third years, but there was no mortality up to the fourth year. In every way, Leucaena leucocephala performed better than desmanthus in Hawaii, but desmanthus is non-toxic (Takahashi and Ripperton, 1949). At Sigatoka in Fiji, desmanthus yielded an average of 7590 kg. DM/ha, of which 64 percent was produced in the wet season and 26 percent in the dry season in a 2000-mm rainfall regime (Payne et al., 1955). At the Kimberley Research Station in northern Australia, Parbery (1967a) obtained dry-matter yields of 35.08 tonnes/ha/year without added nitrogen on Cunnunurra clay and 26.05 tonnes/ha with 100 kg./ha of added nitrogen, cutting the whole plant. When the foliage above 45 cm only was taken, he harvested 63.29 tonnes/ha unfertilized and 70.33 tonnes/ha with 100 kg. added N per hectare, each from four cuts per year. It is sown on a well-prepared seed bed at 2 kg./ha and at a depth of 1 to 1.5 cm. The seed should be treated with concentrated sulphuric acid for 8 minutes to break dormancy. It is regarded as a useful forage plant in Argentina (Burkart, 1943) and Colombia (Bermudez et al., 1968). It appears to fix ample nitrogen. Nutritional Quality and Animal Production The crude-protein content of the whole plant cut at 61-, 91- and 122-day intervals was 10.55 percent, 12.27 percent and 15.52 percent respectively and the average protein content of the leaves was 22.4 percent and of the stems 7.10 percent. Leucaena surpassed desmanthus in protein percentage by one-third. Whyte et al. 1955 ; Le Houérou 1980e ; Skerman 1977 ; Skerman et al. 1991 ; Lock 1989.
Additional Information by Dr. P. Izaguirre de Artucio |