17

4: Forages

Clitoria ternatea L.

Sp. Pl.: 753 (1753).

LEGUMINOSAE

2n = 16

Clitoria zanzibarensis Vatke (1878), Clitoria tanganicensis Micheli (1897), Clitoria mearnsii De Wild. (1925).

Butterfly pea, K(C)ordofan pea, blue pea, Asian pigeon-wings (En). Indonesia: bunga biru (Malay), kembang telang (Javanese, Sundanese). Malaysia: bunga biru, kacang telang. Philippines: kolokanting (Tagalog), giting princesa (Bikol), balog-balog (Visaya). Cambodia: rum'choan. Laos: 'ang s'an dam, bang s'an dam. Thailand: anchan. Vietnam: dâu biê'c.

Clitoria ternatea is pantropical (20 °N-24 °S). Its true origin is obscured by extensive cultivation or naturalization in the humid lowland tropics of Asia, Africa, the Pacific Islands, and the Americas. It is widespread throughout South-East Asia.

Butterfly pea has a reputation as a potential fodder plant, hay or cover crop. It has been extensively tested as such, especially in the subhumid to semi-arid tropics. It has never been used in extensive areas, although it is used by smallholders. It is used as a cover crop in coconut in southern India and in rubber in Malaysia. It is widely grown as an ornamental on fences and trellises because of its showy blue or white flowers, and is grown for dye production and medicinal purposes in India. In the Philippines young pods are eaten as a vegetable.

Nitrogen concentrations of whole tops range from 1.7-4.0% depending on the season and stage of growth. For example, in Brazil, hay cut every 42 days had 3.7% N whereas hay cut every 84 days had 3.0%. Hays from Brazil and India contained 24-38% crude fibre, 38-47% acid detergent fibre, 11-16% lignin and 21-29% cellulose (44% crude cellulose).
Seeds contain 38% protein (2.5% lysine), 5% total sugars, 10% oil and a powerful cathartic compound. Seed size ranges from 15-35 seeds/g.

Perennial climbing, scrambling or trailing herb with a strong woody rootstock. Stems do not root at the nodes, slender, 0.5-3 m long, mostly pubescent or glabrescent, sometimes suberect at the base. Leaves pinnate with 5 or 7 leaflets; leaflets elliptical, oblong, oblong-lanceolate, or almost round, 1-7 cm x 0.3-4 cm, acute, rounded or emarginate at the apex, acute to rounded at the base, glabrescent above, adpressed pubescent beneath; petiole 1-3 cm long; rachis 1-6 cm long; petiolules 1-3 mm long; stipules persistent, lanceolate, (2-)4-10 mm long, veined. Flowers axillary, solitary or paired; peduncle 3-10 mm long; pedicel 6-9 mm long and twisted 180ø so that the standard is held lowermost; bracteoles ovate or round, 4-17 mm x 2.5-15 mm, veined; calyx pubescent, veined, tube 8-12 mm long, lobes oblong-lanceolate or triangular, 7-10 mm x 2.5-3 mm, acute or acuminate, the upper pair joined for less than one third of their length; standard oblong-obovate, 25-50 mm x 15-35 mm, white or greenish-white often blue margined or entirely blue, basal central area often yellow or greenish, very finely puberulous, margins sometimes finely ciliate. Pod linear-oblong, flattened, 6-12.5 cm x 7-12 mm, margined, apiculate, glabrous or with a mixture of sparse adpressed long hairs and very short hairs. Seeds 8-10, ellipsoid, oblong or oblong-reniform, sometimes truncate at one end, 4.5-7 mm x 3-4 mm, 2-2.5 mm, olive, pale brown or deep reddish-brown with dark mottling, or almost black, minutely pitted.

Germination is epigeal; the radicle emerges within 48-72 hours and seedlings emerge in 3-6 days, depending on planting depth. Early growth is rapid in warm moist conditions.
Growth of established plants is mostly from the apices of the main axis and axillary branches; very few new shoots arise from ground level. Flowers are cleistogamous but a small level of outcrossing occurs. Time to flowering in a collection of 58 lines (sown in January at 19 °40'S) ranged from 7-11 weeks, with most lines flowering 8-9 weeks after sowing. Subsequent flowering flushes overlap pod maturation from the previous flush, and they continue throughout the year in frost-free regions. At higher latitudes in the tropics, there is usually a peak at the end of the wet season and again at the end of the cool season, if moisture is available. Pods mature in 8-10 weeks after flowering and shatter readily once fully dry. Growth is more or less continuous in the humid tropics, or with irrigation in other hot regions. Individual plants may live for several years and grow into large vines if undisturbed.

There is considerable variation in the size of flowers and leaflets. Most 'cultivars' mentioned in the literature to date are ecotypes or agrotypes, not named cultivars in the true sense. However, cultivar 'Milgarra' was released in Australia in 1990.

Butterfly pea is essentially a plant of the humid and subhumid tropical lowlands, but it has a reputation for drought tolerance in the seasonally dry tropics (500-900 mm rainfall) and it has survived moderate frost damage in the subtropics (26 °S). It occurs in grassland, open woodland, bush, riverine vegetation, and disturbed places throughout its natural range.
Butterfly pea grows best in full sun. Its annual rainfall requirements for survival may be as low as 400 mm, but it requires about 1500 mm (or supplementary irrigation) for best production. Its altitudinal range is 0-1600(-1800) m and annual mean temperature range is 19-28 °C.
It has wide soil adaptation (pH 5.5-8.9), but prefers fertile friable soils and grows poorly on infertile sandy soils if not fertilized. It is one of the few herbaceous legumes well adapted to heavy clay soils in the subhumid to semi-arid tropics and the only one with potential in irrigated pasture mixtures on these soils. It will not tolerate flooding or waterlogging.
In the seasonally dry tropics and in cool regions, growth is limited by lack of moisture or low temperatures. Leaves are shed in response to these stresses and top growth may be killed by frost or fire. However, recovery during the following growing season is usually good, provided grazing is not heavy and continuous.

It is propagated by seed and readily self- propagates and spreads under favourable conditions by seed thrown vigorously from the dehiscing dry pods. Seed is also spread in cattle dung.
Normally sown from the beginning until the middle of the wet season at rates of (1-)3-5 kg/ha in well-prepared seed-beds with seed placement 1.5-4 cm deep and lightly covered. Higher rates (5-8 kg/ha) may be required when sowing pastures in rough conditions.
Successful stands have been established by broadcasting seed (10 kg/ha) into burnt or heavily grazed grassland, but success is very dependent on good seasonal conditions following planting.
Hand-harvested seed often remains hard-seeded for a long time and requires scarification prior to sowing. Mechanical abrasion, hot water or sulphuric acid can be used to break this dormancy. Mechanically harvested or threshed seed is usually satisfactory for sowing the following wet season without further treatment.
Inoculation of butterfly pea seed with rhizobia is not usually necessary; but, if it is required, broad spectrum cowpea inoculum should be used.

Butterfly pea competes fairly well with weeds once established and can cover the ground in 4-6 weeks when sown at a population of 4 plants/m². Establishment may be a problem on fertile soils if sown with a vigorous companion grass or oversown into an existing pasture. It combines better with tussock than stoloniferous grasses in mixed pastures.
If a pure stand is required (e.g. for seed production), cultivation or hand weeding will be required during early growth. Alternatively, trifluralin (800 g/ha) may be incorporated pre-planting to control grass weeds, and bentazone may be used at rates up to 1900 g/ha to control susceptible broad-leafed weeds. Because butterfly pea is very palatable it must be carefully managed to avoid overgrazing and loss of the stand. The location of its growing points at the ends of the main branches makes it susceptible to frequent low cutting as well as to continuous heavy grazing (for example, it did not persist in irrigated pastures on a heavy clay soil in northwest Australia when grazed at a stocking rate of 2.5 steers/ha). Superphosphate fertilizer application will increase DM yield and plant density on infertile soils.
For seed production on a small scale, plants may be grown on trellises to maximize yield and to make hand harvesting easier. However, for large-scale mechanized seed production, butterfly pea is best grown as an annual row crop suitable for direct heading.

Various fungi (e.g. Cercospora, Colletotrichum, Oidium and Rhizoctonia) and nematodes (Meloidogyne and Pratylenchus) have been recorded on butterfly pea but damage is rarely bad and control measures are unpractical or uneconomic in pastures. Fungicides such as benomyl may be useful in seed crops if diseases break out. Grass hoppers and leaf-eating caterpillars have caused damage in Australia.

Pasture forage is normally harvested by direct grazing or as cut-and-carry forage. Rotational grazing is preferred rather than set stocking whenever the plants are growing actively. Butterfly pea makes good quality palatable hay but it is difficult to harvest and handle because of its viny nature.

Yields of butterfly pea vary enormously because of highly variable growing conditions and management. Moreover, levels of productivity projected from short-term trials are probably unrealistic because of its susceptibility to frequent cutting. For example, when mixed pastures in Colombia were harvested every 6-8 weeks, the amount of butterfly pea in the sward declined from 25-35% to 5% in one year. Worldwide, reported DM yields have ranged 0.2-16.5 t/ha in forage crops and pastures. Crops grown under irrigation on good soils in the lowland dry tropics generally 7-13 t/ha DM, whereas dryland crops usually 3-5 t/ha on good soils and 1-2.5 t/ha on light soils or under low rainfall.
Under upland conditions in the Philippines butterfly pea produced only 0.1-0.6 t/ha forage DM in the first season and 1.3-2.8 t/ha in the second when grown as an intercrop with grain legumes under dry conditions. When sown following rice under lowland conditions the DM of butterfly pea was 8.8 t/ha (4 cuts) as a forage crop and 3.6 t/ha (3 cuts) as an intercrop with mungbean (Vigna radiata (L.) Wilczek). Lablab purpureus (L.) Sweet produced twice as much forage as an intercrop but it reduced mungbean grain whereas butterfly pea did not.
Seed may reach 300 g/plant hand harvested but it varies widely among lines. Yields of up to 700 kg/ha have been recorded for direct headed seed crops in northeast Australia.
Liveweight gain of steers on irrigated pastures in northeast Australia was 0.68 kg/head per day over 41 weeks for a mixture of butterfly pea and para grass (Brachiaria mutica (Forssk.) Stapf) compared with 0.58 kg/head per day for centro (Centrosema pubescens Benth.) and para grass. In Mexico, cattle grazing butterfly pea and pangola grass (Digitaria eriantha Steudel) produced 0.40 kg/head per day over 16 weeks compared with 0.24 kg/head per day from siratro (Macroptilium atropurpureum (DC.) Urban) and pangola grass, but both groups were also fed 1.5 kg/head per day of supplement containing 11.5% crude protein and 64% TDN.

The main collections are held at ATFGRC (CSIRO, Australia) and CIAT (Colombia).

Variation exists among lines in flowering time, pod dehiscence, seed and total dry matter yield, and plant habit. No programmes are known but a major objective would be to improve persistence under grazing and cutting, perhaps by developing forms with more growing points at ground level.

Butterfly pea has been considered a promising forage plant wherever it has been evaluated throughout Australia, Africa, Central and South America and South-East Asia. It may have wider application to smallholder farm systems in South-East Asia. Its drought tolerance and adaptation to heavy clay soils, and the palatability and quality of its forage, suggest it could be used to improve natural grassland in extensive farm systems in the subhumid to semi-arid tropics, given appropriate grazing management. Its susceptibility to close grazing or cutting is a major limitation to general use.

Crowder, L.V., 1974. Clitoria ternatea (L.) Due. as a forage and cover crop - a review. Nigerian Agricultural Journal 11: 61-65.
Gillett, J.B., Polhill, R.M. & Verdcourt, B., 1971. 44. Clitoria. In: Milne-Redhead, E. & Polhill, R.M. (Editors): Flora of tropical East Africa. Leguminosae 4 - Papilionoideae 2. Crown Agents for Oversea Governments and Administrations, London. pp. 515-518.
Hall, T.J., 1985. Adaptation and agronomy of Clitoria ternatea L. in northern Australia. Tropical Grasslands 19: 156-163.
Reid, R. & Sinclair, D.F., 1980. An evaluation of a collection of Clitoria ternatea for forage and grain production. CSIRO, Australia, Division of Tropical Crops & Pastures, St Lucia, Queensland. Genetic Resources Communication No 1. 8 pp.
Skerman, P.J., Cameron, D.G. & Riveros, F., 1988. Tropical forage legumes. FAO, Rome. pp. 258-261.

I.B. Staples

Staples, I.B., 1992. Clitoria ternatea L.. In: Mannetje, L.'t and Jones, R.M. (Editors): Plant Resources of South-East Asia No 4: Forages. PROSEA Foundation, Bogor, Indonesia. Database record: prota4u.org/prosea