Common Name: Calopo
Calopo is a short-lived, vigorous, creeping, twining or trailing herb, that can send out stems up to several metres long and form a tangled mass of foliage 30 - 50 cm deep[
The plant is often grown as a green manure in the tropics[
]. Calopo was introduced into tropical Africa and Asia in the early 1900s and to Australia in the 1930s. It was taken into use as a green manure and cover crop in Sumatra in 1922 and soon thereafter in the rubber and sisal plantations of the central and eastern parts of Java. It was then brought to Malaysia as a cover crop for rubber. Calopo became naturalized in Indonesia and Malaysia, and has spread to most humid tropical areas of the world.
Tropical America and the West Indies.
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Calopo is a plant of the hot humid tropics, where it succeeds at elevations from sea level to 2,000 metres, though it is best adapted to elevations of 300 - 1,500 metres[
]. It grows best in areas where the annual rainfall exceeds 1,250 mm[
]. Plants are not tolerant of frost[
Vigorous growth occurs on soils of all textures[
]. Succeeds in very acid soils with a pH as low as 4.5 - 5[
]. Requires a sunny position - growth declines markedly if the plant is shaded[
]. Plants are moderately drought-tolerant but may die out if the dry season is prolonged[
Calopo grows rapidly and is able to cover the soil in 3 - 6 months after sowing and even sooner on newly cleared, fertile land. It forms a dense entangled sward in 4 - 5 months after sowing, but the plants are short-lived and may only persist for 1 - 2 years[
When grown as a cover crop in plantation crops in a mixture with tropical kudzu and centro, calopo is the first to become established but also the first to be shaded out. Long-term persistence is through recruitment of new plants from seedlings.
The root system is dense and rather shallow, its deepest roots reaching a depth of about 50 cm[
Flowering in calopo is initiated by short days. It is self-pollinated and seeds freely[
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[
A valuable pioneer legume, planted as a green manure to protect the soil surface, reduce soil temperature, fix atmospheric nitrogen, improve soil fertility and control the growth of weeds[
]. It is an important cover crop for plantation crops, especially rubber and oil palm, where it is often grown in a mixture with centro (Centrosema pubescens) and tropical kudzu (Pueraria phaseoloides)[
Calopo grows vigorously, shedding a large amount of leaf litter onto the soil which smothers most weeds[
The effect of calopo and associated legumes in improving soil fertility may last for 14 - 16 years. In an experiment in Malang, Indonesia, a green manure crop of calopo grown for 3 months contained about 65 kg/ha nitrogen in its leaves, shoots and roots[
Calopo is usually propagated by seed, sown at 1-3 kg/ha. Seed is normally drilled in rows when sown into new plantations or broadcast in stands to be used for forage production. After seed is broadcast, the seed-bed may be rolled to improve establishment. Newly harvested seed usually has more than 75% hard seed. Mechanical scarification, soaking in concentrated sulphuric acid for 30 minutes, or soaking in hot water (75°C) for 3 minutes is recommended to enhance germination. Although calopo stems root at the nodes when in contact with moist soil the establishment of stem cuttings inserted directly into soil is generally poor. Use of pre and post-emergence herbicides or hand weeding promotes the establishment of calopo. As calopo nodulates promiscuously with native rhizobia, seeds are usually not inoculated. If inoculum is applied, then cowpea strains such as the Australian CB 756 are used. When planted as a cover crop in plantations it is usually sown in a mixture with other legumes such as Calopogonium caeruleum, Centrosema pubescens and Pueraria phaseoloides with 1-3 kg/ha of calopo in a total mixture of 10- 15 kg/ha of legume seed. When sown for forage production, calopo has been successfully used in mixtures with stoloniferous grasses, such as molasses grass (Melinis minutiflora Beauv.) and Rhodes grass (Chloris gayana Kunth), and with tussock grasses such as setaria (Setaria sphacelata (Schumacher) Stapf & Hubbard ex M.B. Moss). Good results have been obtained from oversowing it into existing stands of pangola grass (Digitaria eriantha Steud.) which have been harrowed
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