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Vigna parkeri Baker. |
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Leguminosae V. gracilis auct., non (Guill. and Perr.) Hook.; Dolichos maranguënsis Taub.; V. maranguënsis (Taub.) Harms. Creeping vigna (Australia). A perennial climbing or prostrate legume, sometimes forming mats 0.1 to 2 m long. Main root-stock rather slender but tough. Stems slender, often rooting at the nodes, sparsely to rather densely covered with mostly spreading hairs. Three leaflets, round, ovate or ovate-lanceolate, 1 to 8.8 x 0.8 to 5.4 cm, rounded to acuminate at the apex, rounded to subacute at the base, pubescent on both faces, margins densely ciliate; petiole 1 to 8.5 cm long. Two petiolules, about 3.5 mm long. Stipules persistent, lanceolate, 2.5 to 8 mm long, prolonged below the point of insertion and bilobed at the base. Two to five inflorescences, axillary, sometimes 10-flowered. Rachis 0.5 to 2.5 cm long, glandular-nodular. Peduncle 2 to 13 cm long. Pedicels 1 to 3 mm long. Calyx sparsely pubescent, tube 1.5 to 2 mm long, lobes deltoid, ovate or lanceolate, 1 to 1.5 mm long, the upper pair joined to form a more-or-less rounded lobe. Standard blue, turning purple-blue, yellow or white, usually paler at the base, oblate, 5 to 8.5 (12) x 5 to 8 (10) mm, glabrous. Wings blue, purple at the tips or yellow. Keel greenish with purple tip or yellowish, the beak not curved inwards. Pods linear-oblong, compressed 1.3 to 2 (0.9 to 3) cm long, 4.5 to 5.5 cm wide, pubescent or glabrescent, two- to five-seeded. Seeds grey to brown with black mottling, oblong-ovoid, 3 to 4 x 2 to 3 mm, 2 mm thick (Gillett, Polhill and Verdcourt, 1971).In addition to ssp. parkeri, which is rare, there are two other subspecies in East Africa: maranguënsis (Taub.) Verde. (syn. V. maranguënsis [Taub.] Harms.), and ssp. acutifolia Verde. (Gillett, Polhill and Verdcourt, 1971). Ssp. maranguënsis occurs in Zaire, Rwanda and Angola to Ethiopia (?), generally from 1 000 to 2 460 m in elevation and sometimes as high as 2 700 m. It is extremely common in East Africa. Ssp. acutifolia occurs in Kenya, Tanzania, Zanzibar and Mozambique from sea level to 1 000 m in elevation (Gillett, Polhill and Verdcourt, 1971). V. parkeri is typical warm-season species, its growth pattern more closely resembling that of greenleaf desmodium than siratro in south-east Queensland, Australia. Frost tolerance and regrowth after frosting Top growth is killed by even light frosts but stands regenerate readily from the root-stock. Early season growth is often rather slow, possibly owing to lack of moisture during this rather dry time of year in south-east Queensland (B.G. Cook, personal communication). Initially considered essentially a plant for wet areas, V. parkeri is now believed to be adapted to most areas that will carry greenleaf desmodium in south-east Queensland, that is areas with annual rainfall exceeding 1 200 mm and with good moisture-holding soils. Established plants have little drought tolerance and are readily killed by dry conditions. Where these conditions occur only infrequently, regeneration from seed in the soil rapidly occurs. Soil seed reserves ranging from 50 to more than 1 000 seeds/m2 (mean 450) have been measured (B.G. Cook, personal communication). While V. parkeri is regarded as a useful plant for seasonally wet areas in south-eastern Queensland, and has persisted for over 20 years in one area subjected to intermittent flooding, CQ 1374 was in the fourth and least tolerant group of 17 legumes tested for flooding tolerance in pots at the University of Queensland. In this group, no plants survived and no adventitious roots were formed when flooding was imposed at first flowering for 10 or 21 days. Others in this group were glycine, axillaris, silverleaf desmodium, centro and lablab (Whiteman et al., 1984). The true picture is therefore unclear. The main soil requirement for V. parkeri appears to be a good moisture-holding ability, so adequate depth of the useful profile is important. V. parkeri persisted and spread from old trial plots on soils with pH as low as 4.6, acid and bicarbonate P levels as low as 7 and 13 ppm respectively, and exchangeable and replaceable K levels as low as 0.09 and 0.13 percent respectively in south-east Queensland (B.G. Cook, personal communication). V. parkeri nodulates with a wide range of Rhizobium strains. Eleven of 19 strains tested, including CB 756, gave yields equal to or in excess of the nitrogen-fertilized controls (Pentney, Whiteman and Sivasupiramiam, 1984). Material planted during the 1960s has survived and spread away from the trial sites in a number of areas in south-east Queensland. It has spread into areas carrying, among other species, Imperata cylindrica and Pennisetum clandestinum (B.G. Cook, personal communication).Land preparation for establishment Naturally, a well-prepared seed bed will give the best establishment from sparse seed, but the plant has the ability to establish into lesser quality seed beds as well. Shallow planting is indicated. 2 kg. seed/ha. Plant at the break of the season. 75 000 for CQ 1374 (B.G. Cook, personal communication).Seed treatment before planting Up to 96 percent hard seeds have been recorded in freshly harvested samples, so that seed scarification is essential (B.G. Cook, personal communication). Nutrient requirements have yet to be investigated, though the plant will persist and spread on fairly infertile soil. It will almost certainly respond strongly to fertilizer application.Compatibility with grasses and other legumes While the main stolons stay close to the ground surface, secondary branches from the leaf axils can climb up to the light through taller-growing species. V. parkeri is particularly compatible with the sward-forming species pangola and Kikuyu, but as long as the stand is not dense and undergrazed it is also able to persist in setaria stands. It is more akin to Lotononis bainesii cv. Miles and Trifolium semipilosum cv. Safari in its growth habits and species compatibility than to the more robust twining legumes (B.G. Cook, personal communication). Stands are inclined to be slow to start, although in pots the plants established rapidly, forming 10 or more stolons per plant at 15 weeks from sowing. These stolons creep readily and root rapidly from the nodes (Pentney, Whiteman and Sivasupiramiam, 1984). Associated grasses generally show signs of nitrogen input, and nitrogen levels in the legume dry matter in excess of 3 percent have been recorded for CPI 25378 (B.G. Cook, personal communication). Because of its growth habit, V. parkeri can tolerate somewhat heavier grazing pressures than the robust twining species such as siratro. It does not, however, tolerate as severe use as Trifolium semipilosum.Dry-matter and green-matter yields Under infrequent harvest regimes V. parkeri is not a high-yielding, bulky species, which is why it was initially passed over during selection of such species as greenleaf desmodium and siratro, but it is nevertheless able to contribute quite a useful yield. None known. Harvesting methods have yet to be developed. As V. parkeri is a rather low-growing plant and the pods shatter readily, it is likely that conventional header harvesting will still be possible from well-grown stands. As blue-flowered material does not flower until May/June, it will be necessary to plant in areas that remain frost free in early winter in order to achieve mature seed crops. The yellow-flowered lines have a much longer flowering period, beginning as early as October. V. parkeri occurs in grasslands, grasslands with scattered trees, thickets, forests and sometimes as a weed of cultivation. Ssp. maranguënsis was long known to agronomists as V. gracilis. It is not V. gracilis (Guill. et Pers.) Hook. (syn. Dolichos gracilis Guill. et Pers.), which comes from the region of the Senegal and Gambia rivers in eastern Senegal and western Mali. Ssp. maranguënsis is a fine legume, often forming natural mixtures with grasses on moist ground in East Africa and producing excellent grazing (Bogdan, 1977).This plant was introduced into Australia in the 1950s and early 1960s as V. gracilis and widely tested before it was passed over for higher yielding plants such as desmodiums and siratro. However, these early plantings of a range of accessions have survived and spread in the Beerwah, Cooroy and Gympie districts of coastal south-east Queensland. As a result, since 1975 it has been under consideration as a plant for use in low lying moist areas in these above 1 200 mm rainfall districts. Its possible suitability to a wider range of habitats is also being appreciated. Cultivar 'Shaw' was released by the Queensland Herbage Plant Liaison Committee in August, 1984. Previously it was identified as CQ1374, but is believed to be derived from CPI 25378, from Entebbe, Uganda, received in 1958.
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