Cajanus cajan (PROSEA)
Cajanus cajan (L.) Millsp.
- Protologue: Field Columb. Mus. Bot. 2(1): 53 (1900).
- Family: Leguminosae
- Chromosome number: 2n = 22, 44, 46
- Cytisus cajan L. (1753),
- Cajanus indicus Spreng. (1826).
- Pigeonpea (En)
- pois d'Angole, ambrevade (Fr)
- Indonesia: kacang bali, kacang gude, kacang kayu
- Malaysia: kacang, kacang dal, kacang hiris
- Philippines: tabios, kardis, kidis
- Thailand: thua rae, thua maetaai, ma hae
- Vietnam: cay dau chieu, dau sang, dau thong
- Laos: thwàx h'ê
- Cambodia: sândaèk dai, sândaèk kroëb sâ, sândaèk klöng.
Origin and geographic distribution
Pigeonpea originated in India and spread to South-East Asia in the early centuries of our era. It reached Africa about 2000 BC or earlier, and found its way to the Americas with the conquests and slave trade, probably through both the Atlantic and the Pacific. Now it is grown all over the tropics, but is of most importance in the Indian subcontinent and East Africa.
In contrast to the Indian subcontinent, where pigeonpea is mainly used as a pulse (dhal = split pea), the use of fresh seeds and even pods as a vegetable in sayors (spicy soups) and other side-dishes preponderates in South-East Asia. Ripe seeds are also eaten roasted. Pigeonpea may replace soyabeans for making tempeh and tahu (fermented products). Pigeonpea is useful as tall hedges on dry soil and on the bunds of paddy fields. The branches and stems can be used for basketry and fuel. It is often grown as a shade crop, cover crop or windbreak, or even as support for vanilla. After establishment, pigeonpea improves the soil by its extensive root system, nitrogen fixation by Rhizobium and the mulch provided by the fallen leaves. It may serve as host for silkworms (Madagascar) or the lac insect (north Bengal, Thailand). Traditional uses as medicine are many, e.g. on Java, young leaves are applied to sores, herpes and itches.
Production and international trade
Pigeonpea covers 3 million ha, of which 85% are in India, and produces 2 million t per year. Major areas are eastern Africa and the Caribbean; in almost 50 countries, the crop is of local importance. In South-East Asia, it is occasionally employed as hedge or garden crop. No reliable statistics exist but the plant has a good potential in drier areas.
Per 100 g edible portion, dry seeds contain: water 7-10.3 g, protein 14-30 g, fat 1-9 g, carbohydrates 36-65.8 g, fibre 5-9.4 g, ash 3.8 g. The energetic value averages 1450 kJ/100 g. Cooking time of dhal varies from 24 to 68 minutes, smaller grains are ready sooner. Fresh seeds contribute vitamins, especially provitamin A and vitamin B complex. Seed weight varies between 4 and 26 g/100 seeds.
- A glandular-pubescent, short-lived perennial (1-5 years) shrub, usually grown as an annual, 0.5-4 m high, with thin roots up to 2 m deep. Stems up to 15 cm in diameter. Branches many, slender.
- Leaves alternate, trifoliolate, glandular punctate; leaflets elliptical, 3-13.7 cm x 1.3-5.7 cm.
- Flowers in pseudoracemes, sometimes concentrated and synchronous (determinate), ussually scattered and flowering over a long period (indeterminate), papilionaceous, corolla yellow or cream, standard dorsally red, orange or purple.
- Fruit a straight or sickle-shaped pod with (2-)4-9 globose to ellipsoid or squarish seeds.
- Seeds white, cream, brown, purplish to almost black, plain or mottled, strophiole usually virtually absent.
- Seedlings with hypogeal germination, first leaves simple.
Growth and development
Emergence is completed 2-3 weeks after sowing, vegetative development starts slowly. After 2-3 months, growth accelerates. Flowering (of 50% of the plants) starts 56-210 days after sowing; maturity ranges from 95 to 256 days in normal conditions with rainy season and long days. Under short days, growth in length is less and flowering accelerated. In Indonesia, flowering and fruiting may continue throughout the year.
Other botanical information
Ten maturity groups may be distinguished under Indian conditions, usually combined into four categories: extra early, early, medium and late-maturing cultivars (120, 145, 185, more than 200 days after sowing, respectively). Continuous variation in present-day world collections shows that formal varieties (var. flavus (DC.) Purseglove and var. bicolor (DC.) Purseglove, described by De Candolle as species) can no longer be maintained.
Flowering is triggered by short days and vegetative development ususally takes place with long days, as in the rainy season of India. There are very few truly day-neutral forms. Optimum temperatures range from 18 to 38°C, frost is not tolerated. Above 29°C, soil moisture and fertility need to be adequate. Rainfall optimum is 600-1000 mm, waterlogging is harmful. Above 2000 m altitude, pigeonpea is rarely found. Drained soils of reasonable water-holding capacity and with pH 5-7 or higher are favourable. Electrical conductivity (salinity) is tolerated from 0.6 to 1.2 S/m.
Propagation is by seed; stem cuttings rarely succeed.
Seeds should be sown in rows with plant spacing 30-50 cm × 75-150 cm. In intercropping, the crop performs well with 2 rows of cereals (e.g. sorghum, millets), cotton or groundnut. After harvest of the intercrop, long-duration pigeonpea continues to grow and protects the soil. As a field crop, pigeonpea may be typified as rather primitive, the tall genotypes in particular are quite cumbersome in cultivation. Weed control is necessary to alleviate slow initial growth. Wind may bend the plants but staking is not practised. Irrigation as a life-saver can be economic; in intensive cropping of short-duration cultivars, irrigation may be required. Mechanization is only possible with short cultivars. Response to fertilizers is rarely economic; a phosphate dressing is generally recommended at 20-100 kg/ha.
Diseases and pests
Because of its long flowering period, pests such as Heliothis borers and Agromyza fruit flies may be compensated for by renewed flushes. Chemical control is cumbersome and expensive in tall indeterminate forms. Crop rotation is advisable against diseases such as Fusarium wilt.
The crop is usually cut near the ground when most pods are mature; many leaves are still green at that stage. Green pods are picked over a long period of time in home gardens or hedge crops. Mechanical harvesting of ripe pods is possible with combine-harvesters, but only for cultivars maturing uniformly with pods at a uniform level above the soil.
In India, yield averages 716 kg/ha. In marginal areas, yield is 700 kg/ha in sole cropping, but under optimum conditions yields of more than 5000 kg/ha are possible. In intercropping with maize in Indonesia low yields of 175 kg/ha were obtained, but in the eastern part of Indonesia sole cropping may produce 3000-4000 kg/ha.
Handling after harvest
Entire air-dried plants are threshed, usually by hand or with cattle, and seed is cleaned. Clean bins prevent insect attack, which can be considerable. Storage as split peas reduces bruchid attack. Processing includes dhal-making, either wet (after sprinkling heaps of seed) or dry, by milling. In the West Indies, canning and freezing of fresh pigeonpeas is a million-dollar export business, for instance to the USA.
The world germplasm collection has covered India and several African countries, and some Caribbean islands for a second time. More than 11 000 samples are available in the ICRISAT collection near Hyderabad, India, and various breeders and institutes have parts of this collection. Attempts are continuing to cover all areas of occurrence.
Breeding for high yield, and for consumer and miller preference are prime criteria. Stability of yield may be obtained by selecting for photoperiod insensitivity, disease and pest resistance, suitablility for intercropping and for multiple harvests. For most of these characteristics, improved genotypes are now available. Resistance is available in wild relatives and there are promising pest-resistant and disease-resistant genotypes. Short-duration Indian cultivars include 'Prabhat', Pusa Ageti', 'Sharda', 'T21', 'UPAS-120'; good medium duration cultivars are 'C 11', 'BDN-1', and several ICP lines. Hybrid cultivars exist too, including 'ICPH 2, 5, 6, 8'. Several wild relatives, e.g. Cajanus albicans (W.& A.) Maesen, C. sericeus (Benth. ex Bak.) Maesen, C. scarabaeoides (L.) Thouars, cross with pigeonpea, the closest one is C. cajanifolius (Haines) Maesen (= Atylosia cajanifolia). Hybrids have contributed male sterility, but the transfer of insect resistance (from C. scarabaeoides), high protein content (several species), improved drought resistance (C. acutifolius (Benth.) Maesen) or annuality (C. platycarpus (Benth.) Maesen) has not yet materialized. In Malaysia, Singapore, Indonesia, Brunei, the Philippines and Papua New Guinea the following wild species are found: Cajanus crassus (Prain ex King) Maesen, C. goensis Dalz., C. platycarpus (Benth.) Maesen, C. reticulatus (Dryander) F. von Muell. var. grandifolius (F. von Muell.) Maesen, C. scarabaeoides (L.) Thouars, C. volubilis (Blanco) Blanco. Accessions from South-East Asia are still lacking in gene banks.
As a multi-purpose crop pigeonpea is well known but ought to be promoted especially in more semi-arid regions of Indonesia (East Java, Sunda Islands) and the Philippines. It fits in smallholders garden cropping and along hedges and bunds of rice fields.
- Dahiya, B.S. 1980. An annotated bibliography of pigeon pea 1900 - 1977. ICRISAT, Patancheru, A.P., India. 183 pp.
- ICRISAT, 1984. Grain legumes in Asia. Summary Proceedings of the Consultative Group Meeting for Asian Regional Research on Grain Legumes (Groundnut, Chickpea, Pigeonpea). ICRISAT Center, 11-15 Dec. 1983. ICRISAT, Patancheru, A.P., India. 98 pp.
- Nene, Y.L. & Kumble, V. (Editors), 1981. Proceedings of the International Workshop on Pigeonpeas. 15-19 Dec. 1980, Patancheru, A.P. India. ICRISAT, India. Vols 1 and 2, 508 and 451 pp.
- van der Maesen, L.J.G., 1985. Cajanus DC. and Atylosia W.& A. (Leguminosae). A revision of all taxa closely related to the pigeonpea, with notes on other related genera within the subtribe Cajaninae. Agricultural University Wageningen Papers 85-4. 225 pp.
- Whiteman, P.C., Byth, D.E. & Wallis, E.S., 1985. Pigeonpea. In: Summerfield, R.J. & Roberts, E.H. (Editors): Grain legume crops. Collins, London. p. 658-698.
- L.J.G. van der Maesen