1

1: Pulses

Cajanus cajan (L.) Millsp.

Field Columbian Museum, Botanical Series 2(1): 53 (1900).

LEGUMINOSAE

2n = 22, 44, 46

Cytisus cajan L. (1753), Cajanus indicus Spreng. (1826).

Pigeon pea (En). Pois d'Angole, ambrévade (Fr). Indonesia: kacang Bali, kacang gude, kacang kayu. Malaysia: kacang, kacang dal, kacang hiris. The Philippines: tabios, kardis, kidis. Cambodia: sândaèk dai, sândaèk kroëb sâ, sândaèk klöng. Laos: thwàx h'ê. Thailand: thua rae, thua maetaai, ma hae. Vietnam: cay dau chieu, dau sang, dau thong.

Pigeon pea originated in India and spread to South-East Asia in the early centuries of our era. It reached Africa 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. It is now grown all over the tropics but especially in the Indian Subcontinent and East Africa.

In contrast to the Indian Subcontinent, where pigeon pea 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 eaten roasted too. Pigeon pea may replace soya beans to make tempeh and tahu (fermented products). Pigeon pea is useful as tall hedges on dry soil and on the bunds of paddy fields. The branches and stems can be used for baskets and fuel. It is often grown as a shade crop, cover crop or windbreak, or even as support for vanilla. After establishment, pigeon pea 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 (northern Bengal, Thailand). Traditional uses as medicine are many, e.g. young leaves are applied to sores, herpes and itches in Java.

Pigeon pea covers 3 million ha, of which 85 % are in India, and produces 2 million t/year. Major areas of production 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 a hedge or garden crop. No reliable statistics exist but the plant can yield well in drier areas.

Per 100 g edible portion of 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 energy content averages 1450 kJ/100 g. Cooking time of dhal is 24-68 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), usually 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.

Emergence is complete 2-3 weeks after sowing. Vegetative development starts slowly. After 2-3 months, growth accelerates. Flowering (of half the plants) starts 56-210 days after sowing. Maturity ranges from 95 to 256 days in normal conditions with rainy season and long days. With short days, growth in length is less and flowering accelerated. In Indonesia, flowering and fruiting may continue throughout the year.

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 and 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 plants grow vegetatively with long days, as in the rainy season of India. There are 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/year, waterlogging is harmful. Pigeon pea is rarely found above altitude 2000 m. Drained soils of reasonable water-holding capacity and with pH 5-7 or more are favourable. The plant tolerates an electrical conductivity (salinity) from 0.6 to 1.2 S/m.

Propagation is by seed. Stem cuttings rarely succeed.

Seeds should be sown in rows with spacing 30-50 cm x 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 pigeon pea continues to grow and protects the soil. As a field crop, pigeon pea may be typified as rather primitive, particularly the tall genotypes being cumbersome in cultivation. Weeds must be controlled 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 for short cultivars. Response to fertilizers is rarely economic; a phosphate dressing is generally recommended at 20-100 kg/ha.

Because of its long flowering period, pests such as Heliothis borers and Agromyza fruitflies 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 then still green. Green pods are picked over a long period in home gardens or hedge crops. Ripe pods can be harvested with combine-harvesters but only for cultivars maturing uniformly with pods at a uniform level above the ground.

In India, yield averages 716 kg/ha. In marginal areas, yield is 700 kg/ha in sole cropping, but with 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.

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 pigeon peas is a million-dollar export business, for instance to the United States.

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 that collection. Attempts are continuing to cover all areas of occurrence.

High yield and consumer and miller preference are prime criteria. Stability of yield may be obtained by selecting for photoperiod insensitivity, disease and pest resistance, suitability for intercropping and for multiple harvests. For most of those 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, Cajanus sericeus (Benth. ex Bak.) Maesen, Cajanus scarabaeoides (L.) Thouars, cross with pigeon pea, the closest one is Cajanus cajanifolius (Haines) Maesen (= Atylosia cajanifolia Haines). Hybrids have contributed male sterility, but the transfer of insect resistance (from Cajanus scarabaeoides), high content of protein (several species), improved drought resistance (Cajanus acutifolius (Benth.) Maesen) and annuality (Cajanus platycarpus (Benth.) Maesen) have 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, Cajanus goensis Dalz., Cajanus platycarpus (Benth.) Maesen, Cajanus reticulatus (Dryander) F. von Muell. var. grandifolius (F. von Muell.) Maesen, Cajanus scarabaeoides (L.) Thouars, Cajanus volubilis (Blanco) Blanco. Accessions from South-East Asia are still missing from gene banks.

As a multipurpose crop, pigeon pea is well known but ought to be promoted especially in more semiarid 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, 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. Vol. 1 (508 pp.) and Vol. 2 (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. pp. 658-698.

L.J.G. van der Maesen

Van der Maesen, L.J.G., 1989. Cajanus cajan (L.) Millsp.. In: van der Maesen, L.J.G. & Somaatmadja, S. (Editors): Plant Resources of South-East Asia No 1: Pulses. PROSEA Foundation, Bogor, Indonesia. Database record: prota4u.org/prosea