Cajanus cajan (L.) Millsp.
|Author: Le Houérou|
Guandul, poroto guandul, poroto paraguayo, sachacafé, falso café, arveja (Argentina), guando (Brazil), quinchoncho (Venezuela), frijol de árbol (Mexico), Cumandái (Paraguay), red gram, tur, arhar, dahl (India), catjang, kachang (Asia), pigeon pea (Australia), pigeon pea, angola pea (United Kingdom), pois d'angole (French-speaking West Africa), Puerto Rican bean, pigeon pea (Hawaii).
Annual, or more usually short-term perennial shrub that may reach 4-5 m in height, but usually 1-2 m only, woody at the base, with a variable habit, but usually erect. Deep and quick growing tap root. Angular stem resulting from three ribs starting from the base of each petiole. Leaves trifoliate, alternate set in a spiral along the stem. Leaflets oblong, lanceolate 5-10 cm long x 2-4 cm wide, pubescent likewise the stem. Lateral petioles, 2-3 mm the terminal one reaching 10-20 mm. Stipules linear 2-3 mm long, stipulets filiform 1-2 mm long. Flowers usually yellow but they may also be striated with purple streaks or plain red. Corolla 20-25 mm, with the flag 18-20 mm wide. Calyx 10-12 mm long, with 5 linear teeth. Inflorescence composed of racemes having 5-10 flowers on top of an axillary, little divided peduncle. Pods flat, with an acuminate tip, pubescent and of variable colour, 5-9 cm long x 12-13 mm wide, containing 2-9 seeds in shades of brown, red or black. Husks bearing deep, oblique furrows underlining the septa between the seeds. Life span, up to 5 years. Pigeon pea is extremely variable from the genetic view point hence the very many cultivars. Reproduction system is ca 60 % autogamous, the chromosomic number is 2n = 22. There are 16,000-18,000 seeds per kg and some 10 % hard seeds.
It is a short-day plant. Gooding (1962) reported two groups of plants in Trinidad one group spans 60 to 106 days in the time taken from sowing to podding, the other up to 237 days. It flowers over about two months as days become shorter, and has flowers and ripe pods on the plant at the same time. It flowers in 98 days in the Kimberley district in northern Australia (lat. 15°S) with pods maturing in 178 days. It flowers in eight months in the Bombay district in India (lat. 20°N). Too much shading causes the plant to make spindly growth and to bear thin, pale green foliage and few pods (Krause, 1932). The growing period lasts from 60 to 235 days, depending on cultivar and latitude.
Cajanus cajan is very heat-tolerant. Prefers hot moist conditions. Under Hawaiian conditions grows between 18 and 30°C. Will grow at temperatures above 35°C under adequate soil conditions of moisture and fertility. Does not tolerate frost, but will grow in temperatures to just above frost level. Will seed as a perennial at 1840 m down to a minimum night temperature of 10°C (Krause, 1932). Subject to frost damage (Schofield, 1945). Tall plants may escape light frosts because of the height of the foliage.
Cajanus cajan is one of the most drought tolerant legume crops, with a wide range of rainfall tolerance, but prefers more than 625 mm and in elevated areas exceeding 2 000 m cold nights and cloudy weather interfere with fertilization of flowers. Flowers well where rainfall is 1 500 to 2 000 mm. On deep, well-structured soil will grow where rainfall is 250 to 375 mm (Krause, 1932).
Tolerates a wide range of soils, from sands to heavy black clays. Tolerates a wide range of pH, but the most favourable range is pH 5.0 to 7.0. It is sensitive to salt spray, high salinity and to water logging. Will grow in sand provided it does not contain more than 0.0005 g of sodium chloride per gram of soil (Krause, 1932).
Of unknown origin, probably Indian and African. Cultivated in ancient Egypt, Africa and Asia since prehistoric times, later introduced to America. Now acclimatized in several tropical countries. The major producer is India with over 100 cultivars, 2.4 million ha cultivated and 90% of world production. Its altitude range is 1250 m in Hawaii (Ripperton and Hosaka, 1942), at heights of 1230 to 1500 m it fails to set seed; 0 to 3000 m in India (Krause, 1932) and Colombia (Crowder, 1960). Essentially a plant of the semi-dry lowlands but has wide adaptability. Generally should not be planted above 770 m. Latitudinal limit is 30° N and S, the optimal being 15-20° for most cultivars.
There are no registered commercial cultivars in Australia, but in India there are numerous varieties. Whyte (1964) reported 86 different types. Commercially there are the late, tall, long-podded, many-grained "arhar" type of north-west and eastern India, and the early, small, few-seeded "tur" type of Madhya Pradesh, western and peninsular India.
Pigeon pea constitutes an important domestic fuel over large areas, albeit its caloric power is low. On certain types of soils such as vertisols the wood production may exceed that of Leucaena. Feed value of the fodder is excellent with 10-15 % CP on the green material DM. But pigeon pea is not always readily accepted by stock that has not acquired a taste for it (Wickens in Litt.,2000). Leaves remain on the plant throughout the dry season. Yields of fodder vary widely with the ecological conditions and the care given to the crop. Tall perennial varieties are amenable to trimming as fodder, but also as green manure (2.6 % nitrogen). The effect of pigeon pea on soil fertility has been studied in detail (Ong & Daniel, 1990). Due to its deep rooting system pigeon pea offers little competition to associated crops and is therefore much used in intercropping systems with cereals such as millet, sorghum and even maize, it also provides a good means to improve fertility in fallows. Fodder yields may reach 25 t DM / ha / yr in close to optimal conditions without fertilization, and 38 t with a 100 kg nitrogen and phosporus applications. Grain yields may vary from 1 to 10 t /ha / yr of shelled grain. Naturally, under the conditions of the South Sahel the expected results are much lower : 2-4 t DM of fodder and stalks plus 600-1,200 kg of clean beans / ha / yr. As a human food, pigeon pea produces, under the Sahel conditions, some 650 kg of beans / ha / yr, having some 25 % crude protein, with a well balanced composition in amino-acids, save for methionine and cystine which are too low for an ideal human food. The pods may be consumed green, used as green peas, or as ripe beans, like cowpea. Nitrogen fixing ability for a density of 7,000-10,000 plants ha is of the order of 100-120 kg N2 / ha / yr (ca 15 mg / pl / yr). The crop has long been used as a windbreak and shade for young coffee trees, forest seedling nurseries and vegetable beds, and is an important honey-producing plant. The canning of green pigeon peas is a major industry in Puerto Rico and Trinidad.
The grain is used for human and stock feed. Straw, husks and screenings are useful roughages. Nearly 2 350 000 hectares are grown in India yearly. In one single harvest in Hawaii, the fully podded tops gave 11.2 tonnes of green forage, 4.97 tonnes of dry matter and 400 kg. protein per hectare (Takahashi and Ripperton, 1949). Cattle fed wholly on pigeon-pea pasture have gained in weight from 0.7 to 1.25 kg. per head per day at a carrying capacity of 1 to 3.75 beasts/ha, and liveweight gains of 200 to 500 kg. per hectare per annum have been recorded (Krause, 1932). In Brazil, von Schaaffhausen (1966) found that Zebu bulls grazing a pangola grass/pigeon pea pasture gained an average of 35 kg. in 90 days during a severe drought, while animals on a control pasture lost 6 kg. On rotation pastures of Lablab purpureus, pigeon pea and grasses, 47 bulls gained 40 kg. in 63 days.
Pigeon pea is harvested for hay and for milling for meal in Hawaii when a large percentage of pods are mature probably two-thirds to three quarters of the pods in sight because a large part of the nutritive value of the plant is contained in the seed. Harvest not more than the upper third of the plant to avoid the woody base unless the plant is spindly. Cure on the cut surface of the plant which has just been harvested for six to eight days and then mill into meal. Pigeon-pea hay is an effective substitute for more expensive industrial concentrates. Otero (1952) recorded that in Brazil it made good silage and was very palatable to the animals. If Cajanus is not frosted, it will stand over very well for winter and dry-season feeding.
The plant has a high feeding value for beef and dairy cattle, swine, sheep and goats. The well-leaved and fully podded branches, cut at 0.8 metres, have 40 to 50 percent dry matter, and protein up to 16 percent of the dry matter (Takahashi and Ripperton, 1949). The plant is also a good source of vitamin A. Otero (1952) recorded 11.46 percent crude protein and 22.6 percent crude fibre in the leaves, and 18.36 crude protein and 5.43 percent crude fibre in the seeds. From silage made from the foliage he recorded 15.09 percent crude protein, 26.05 percent crude fibre, and 32.8 percent nitrogen-free extract in the dry matter. The silage had 66.7 percent crude fibre, and 32.8 percent nitrogen-free extract in the dry matter. The silage had 66.7 percent moisture. The forage is not relished by cattle in the immature stage. Grazing should be deferred to the early green-pod stage (Hosaka and Ripperton, 1944). Mature plants may cause irritation of the rumen of cattle (Stanton, 1966).
Parbery (1967a) harvested 25.45 tonnes of dry matter in 372 days (unfertilized) and 37.96 tonnes/ha when fertilized with 100 kg. N/ha on Cunnunurra clay but only 1 071 kg./ha, unfertilized, on Cockatoo sand in the Kimberley district of northern Australia. One hundred kg. N/ha depressed its yield on Cockatoo sand. The yield of 37.96 tonnes when fertilized with 100 kg./ha represents 7 704 kg./ha of protein. In Colombia, Herrera and Crowder (1963) obtained 14 000 kg. DM/ha and more than 2 000 kg./ha of crude protein from cutting pigeon pea at ground level or at 15 cm when the plants were 150 cm tall. No regrowth occurred when the plants were cut to ground level.
Whyte (1964) records that it is attacked by caterpillars, pod borers, gall fly, wilt (Fusarium udum) and leaf spot. Colbran (1963) found that the roots were attacked by the nematode Helicotylenchus dihystera. In Hawaii it is attacked by the scale insect, Coccus elongatus, a stem borer, termites, a pod borer (Lycaena boetica) and leaf eating caterpillars (Krause, 1932). A 4 percent DDT spray controlled pod borers in Mauritius (Gooding, 1962). The ability to compete with weeds is not high in the seedling stage, but thereafter quickly shades out weeds. Dry season leaf fall also helps suppress weeds (Stanton, 1966). In Puerto Rico it has been affected by spotting of the leaves and pods and seed destruction by Colletotrichum cajani (Krause, 1932). Gooding (1962) reports collar and stem canker caused by Physalaspora and possibly Diplodia, and Hammerton (1975), rust (Uredo cajani).
Gooding 1962 ; Krause 1932 ; Nichols 1964 ; Akinola, Whiteman and Wallis 1975 ; Whyte et al. 1955 ; Berhaut 1975 ; Berhaut 1976 ; NAS 1980 ; Vandenbelt 1988 ; Ong & Daniel 1990 ; Skerman 1977 ; Skerman et al. 1991 ; Dommergues et al. 1999.
It is the opinion of the present writer that pidgeon pea deserves much more attention on the part of agriculture developers in the Sahel than it has received to-date.