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Vigna unguiculata (L.) Walp. ssp. unguiculata

Syn: Vigna sinensis (L.) Savi ex Hassk. Fabaceae
Cowpea, Crowder pea, Black-eyed pea, Southern pea

Source: James A. Duke. 1983. Handbook of Energy Crops. unpublished.

  1. Uses
  2. Folk Medicine
  3. Chemistry
  4. Description
  5. Germplasm
  6. Distribution
  7. Ecology
  8. Cultivation
  9. Harvesting
  10. Yields and Economics
  11. Energy
  12. Biotic Factors
  13. References


Cultivated for the seeds (shelled green or dried), the pods and/or leaves that are consumed as green vegetables or for pasturage, hay, ensilage, and green manure. The tendency of indeterminate cvs to ripen fruits over a long time makes them more amenable to subsistence than to commercial farming. However, erect and determinate cvs, more suited to monocultural production systems, are now available. If ctut back, many cvs continue to produce new leaves, that are eaten as a potherb. Leaves may be boiled, drained, sun-dried and then stored for later use. In the United States, green seeds are sometimes roasted like peanuts. The roots are eaten in Sudan and Ethiopia. Scorched seeds are occasionally used as a coffee substitute. Peduncles are retted for fiber in northern Nigeria. Crop used to some extent as pasturage, especially for hogs, and may be used for silage, for which it is usually mixed with corn or sorghum. Crop is very useful as a green manure, and leafy prostrate cvs reduce soil erosion.

Folk Medicine

Cowpeas are sacred to Hausa and Yoruba tribes, and are prescribed for sacrifices to abate evil and to pacify the spirits of sickly children. Hausa and Edo tribes use cowpeas medicinally, 1 or 2 seeds ground and mixed with soil or oil to treat stubborn boils.


Raw mature seeds typically contain (per 100 g): ca. 11.4% moisture, 338 calories, 22.5g protein. 1.4 g fat, 61.0 g total carbohydrate, 5.4g fiber. 3.7 g ash, 104 mg Ca, 416 g P, 0.08 mg thiamine, 0.09 mg riboflavin, 4.0 mg niacin, and 2 mg ascorbic acid. In results at IITA, based on seveal thousand distinct cvs, protein averaged 23–25%, protein, ranged from 18 to 29%, with potential for perhaps 35%. The proteins consist of 90%, water-insoluble globulins and 10% water-soluble albumins. The reported amino acid content is (mg/g N): isoleucine, 239, leucine 440, lysine 427, methionine 73, cystine 68, phenylalanine 323, tyrosine 163, threonine 225, tryptophan 68, valine 283, arginine 400, histidine 204, alanine 257, aspartic acid 689, glutamic acid 1027, glycine 234, proline 244, and serine 268. Although much variation occurs, cowpeas are deficient in cystine, methionine, and tryptophan. Total sugars range from 13.7 to 19.7% and include: 1.5% sucrose, 0.4% raffinose, 2.0% stachyose, 3.1% verbascose. Starch may vary from 50.6 to 67.0% with 20.9–48.7%, amylose, 11.4–36.6% amylopectin. The fatty acid compostion of Pakistani seed oil is reported as: linolenic 12.3, linoleic 27.4, oleic 12.2, 1.1 lignoceric, 4.0 behenic, 0.9 arachidic, 7.1 stearic, 33,4 palmitic. Seeds also contain 0.025% stigmasterol. Immature pods also contain (per 100 g): 85.3% moisture, 47 calories, 3.6 g protein. 0.3 g fat, 10.0 g total carbohydrate, 1.8 g fiber, 0.8 ash, 45 mg Ca, 52 mg P, 1.2 mg Fe, 170 ug vitamin A, 0.13 mg thiamine, 0.10 mg riboflavin, 1.0 mg niacin, and 22 mg ascorbic acid. Raw immature seeds contain (per 100 g): 66.8% moisture, 127 calories, 9.0 g protein, 0.8 g fat, 21.8 g total carbohydrate, 1.8 g fiber, 1.6 mg ash, 27 mg Ca, 175 mg P, 2.3 mg Fe, 2 mg Na, 541 mg K, 370 IU vitamin A value, 0.43 mg thiamine, 0.13 mg riboflavin, 1.6 mg niacin, and 29 mg ascorbic acid. Tender shoot apices, raw, contain (per 100 g): 89% moisture, 30 calories, 4.8 g protein, 0.3g fat, 4.4 g total carbohydrate, 1.8 g ash, 73 mg Ca, 106 mg P, 2.2 mg Fe, 0.35 mg thiamine, 0.18 mg riboflavin, 1.1 mg niacin, and 36 mg ascorbic acid. The hay contains per 100 g: 9.6% moisture, 18.6 g crude protein, 23.3 g crude fiber, 2.6 g fat, 34.6 g N-free extract, and 11.3 g ash. Digestibility is improved by grinding the seeds into a fine powder. Seeds contain a trypsin inhibitor, a chymotrypsin inhibitor and a cyanogen in concentrations of ca. 2 mg/100 ml extract. Cooking improves the nutritive value, perhaps because the activity of trypsin inhibitors and/or the amount of other toxins are decreased by heat.


Annual herb, erect or suberect, spreading, to 80 cm or more tall, glabrous, taproot stout with laterals near soil surface, roots with large nodules, stems usually procumbent, often tinged with purple, first leaves above cotyledons are simple and opposite, subsequent trifoliolate leaves are alternate, the terminal leaflet often bigger and longer than the two asymmetrical laterals, petiole, stout, grooved, 5–15 cm long; leaflets ovoid-rhombic, entire or slightly lobed, apex acute, 6.5–16 cm long, 4–11 cm wide, lateral leaflets oblique; inflorescence axillary, 2–4-flowered, crowded, near tips on short curved peduncles 2.5–15 cm long; calyx campanulate with triangular teeth, the upper 2 teeth connate and longer than rest; corona dull white, yellow, or violet with standard 2–3 cm in diameter, keel truncate; stamens diadelphous, the anthers uniform; pods curved, straight or coiled; seeds 2–12 mm long, globular to reniform, smooth or wrinkled, red, black, brown, green buff or white, as dominant color; full colored, spotted, marbled, speckled, eyed, or blotched; (5–30 g/100 seeds, depending on the cv). Germination phanerocotylar. Fl. early summer. Fr. mid- and late summer, depending on the cv sensitivity tp ;pca;photoperiod and tmperature conditions.


The most sensitive collection of germplasm (and literature) is at IITA (over 7,000 cv accessions in 1975). Cowpea cvs may be grouped in the following manner for the United States: 'Crowder peas': seeds black, speckled, brown, or brown-eyed, crowded in pods, seed usually globose; 'Brown Crowder' a good cv in Puerto Rico; 'Black-eyed': seeds white with black-eye around hilum, not crowded in pods. Extensively grown in California and southeastern United States and Puerto Rico; 'Cream' cvs: seed cream-colored, not crowded in pods; intermediates between 'Crowder' and 'Black-eyed' types, as 'Purple Hill' with deep purple mature pods and buff or maroon eyed seed; forage cvs: as 'New Era,' useful also for dry seeds in other geographical locations, e.g. western Africa. Other standard cvs are: 'Block,' 'Brabham,' 'Early Bluff,' 'Iron,' 'Taylor,' and 'Victor.' 'Gub-gub' is an excellent table cv. Assigned to the African and Hindustani Centers of Diversity, cowpea or cvs thereof as reported to exhibit tolerance to aluminum, drought, high pH, heat, laterite, low pH, nematodes, poor soil, shade, slope. virus, weeds, and wilt. (2n = 22.)


Of ancient culture in Africa and Asia, and widespread in Africa, spreading by way of Egypt or Arabia to Asia and the Mediterranean. Now widely cultivated throughout the tropics and subtropics. Wild and cultivated forms readily cross. Steele (1972) and Sauer (1952) agree on a solely Ethiopian center of origin, followed by subsequent evolution predominantly In the ancient farming systems of the African Savanna.


Thrives on many kinds of soil, from highly acid to neutral; less well adapted to alkaline. Crop grows and yields at relatively low fertility levels, but often responds to P fertilization, N applications rarely effective on well-nodulated plants. Can withstand considerable drought and a moderate amount of shade, but is less tolerant of waterlogging than soybean. Some plants are indeterminant in growth, and continue to grow until killed by frost. In the tropics, such indeterminate plants may be weak perennials and continue growing as long as conditions are favorable. In some determinate types, the later flower initiation, the higher up the stem it is, the more flowers, and the greater the ultimate seed yield providing the growing season is sufficiently long. Dry matter production, seed yield, and root nodulation are reduced in photoperiods less than 12 hr, 13 min. Differences of as short as 12 min can affect flowering and seed yield. Cowpeas are short-day, warm-weather plants, sensitive to cold and killed by frost. They tolerate heat and relatively dry conditions and can be grown with less rainfall and under more adverse conditions than Phaseolus vulgaris or P. lunatus. Over a range of 21°C day/16°C night to 36°C day/ 31°C night dry matter production was greater at 27°C day/22°C night. Night temperatures strongly affect many phases of the life cycle and differences in day temperature during reproductive growth markedly affect crop duration and yield. Marked cv differences in environmental responses have been identified. Ranging from Warm Temperate Thorn to Moist through Tropical Thorn to Wet Forest Life Zones, cowpea is reported to tolerate anntial precipitation of 2.8–41.0 dm (mean of 54 cases = 14.2). Annual mean temperature of 12.5° - 27.8°C (mean of 54 cases = 22.1), and PH of 4.3–7.9 (mean of 46 cases = 6.2).


Seeds remain viable for several years. Germination is epigeal. Should be planted after danger from frost is past. If seeded for hay or seed, crop should be sown early, but for green manure and pasture purposes, may be seeded late with good results. Rate of seeding varies with method: when planted in rows 10–40 kg/ha, for broadcasting, 90 kg/ha. Cowpeas may be planted in rows, broadcast, or mixed with such other plants as cassava, corn, sorghum, sudangrass, johnsongrass, millets, peanuts, or soybeans. When grown for seed, it is painted in rows, for forage or green manture, broadcast. For hog feed or silage, cowpeas are planted with corn, either at the sime time as or at the last cultivation of corn. In rows, cowpeas are spaced of 5–7.5 cm apart, in rows 75–90 cm apart two or more cultivations are necessary to control weeds. Ordinary corn cultivator equipment is satisfactory, and cultivation should stop when flowering begins. In United States, 600–1,000 kg/ha of a 4-8-8 NPK fertilizer may be applied in bands 5 cm below seeds when planting. Cowpeas are usually grown rainfed, rarely irrigated. For weed control, amines of 2-4-D and MCPA are said to be effective as preemergence sprays. Trifluralin at 0.56–1.12 kg/ha just before sowing is said to give good control. Cowpeas respond slightly to K application up to 45 kg/ha. Calcium ions in the soil aid inoculation. In the United States, application of ca. 1 MT of lime is recommended and favors seed increase more than hay increase. Superphosphate recommendations are 112–224 kg/ha in the United States. Sulfur can limit seed production and/or protein synthesis. Molybdenum recommendations are 20–50 g/ha, and Mn, Cu, Zn, and B are essential, in very small quantities, for effective nodulation and seed yield increases. The cowpea symbiosis has genetic potential for large seed yields: cowpea Rhizobium associations should require only nominal amounts of fertilizer N, if any.


Early maturing cvs produce pods in 50 days, seed in 90 days, late cvs mature seed in 240 days. Crop ripens unevenly and proper Stage for harvesting is difficult to determine. Usually flowers and green and ripe pods occur on vines at same time. Crop is cut for seed when one-half to two-thirds of pods are ripe. May be harvested by hand, with a special harvester or by self-rake reapers. For hay, crop cut when most pods are fully developed, and first ones have ripened. If cut too early, hay is difficult to cure; if cut too late, stems are long and woody and seed and leaves shatter badly. Ordinary mowing machine is used for harvesting cowpeas.

Yields and Economics

Yields vary with cv climate, soil, and culture. Yields are: in the tropics, 400–600 kg dried beans/ha: in the United States, 1,000–1,500 kg/ha, but up to 3,000 kg/ha in California. World production in 1975 from 5,170,000 ha was 1,097,000 MT seed, (212 kg/ha). Africa produced 1,003,000 MT (199 kg/ha); North America, 57,000 MT (715 kg/ha); Asia, 27,000 MT (629 kg/ht); Europe, 6,000 (803 kg/ha). Oceania produced 3,000 MT, averaging 633 kg/ha. Nigeria had the highest national production with 850,000 MT; Upper Volta, 75,000, Haiti, 37,000, Senegal, 23,000, and United States, 20,000. Highest reported national yields were Trinidad with 3,457 kg/ha, Egypt, 3,103, Sri Lanka, 1,107, Japan, 1,000; and Greece, 803 (FAO, 1976). With good cvs and integrated insect control, yields of 2,000 kg/ha would be feasible. Cowpea is the second most important pulse in tropical Africa and in Tropical America, especially Venezuela (ca. 35,000 ha) and Brazil (ca. 400,000 MT). In the United States cowpeas ranked 36th in acreage in 1965 and 30th in value ($3.5 million). World producuon was estimated then at 272,000 MT annually (probably conservative). In southeastern United States cowpeas are grown mainly for green pods and green seeds in southeastern United States and for dry beans in California.


According to the Phytomass Files (Duke, 1981b), NPP ranges from 3–6 MT/ha. But the global average N-fixation rate for this important intercrop is ca 200 kg/ha (Duke 1981b). Vigna aconitifolia is reported to have NPP of 6–8 MT/ha/yr; V. marina, 7–9; V. radiata, 6; V. umbellata, 4–10.

Biotic Factors

In either dry or humid areas ofUnited States and Africa, cowpeas almost entirely self-pollinated. Some outcrossing (10–15%) probably almays occurs with ants, flies, and bees as the main vectors. Flowers open early in morning, close by noon and fall off the same day. Pollen is sticky and heavy. Grasshoppers may be the worst pests of cowpeas but are not serious in western Africa; where Maruca tesulalis, Enarmonia pseudonectis and some Heliothis spp. damage foliage, flowers, buds and pods; thrips and leafhoppers damage foliage, and bruchids damage dry seeds. In southeastern United States, the cowpea curculio is the most serious pest. Other insects recorded as attacking cowpeas are: southern cowpea weevil (Callosobruchus maculatus), fall armyworm (Spodoptera frugiperda) green cloverworm (Plathypena scabra): bean leaf beetle (Cerotoma trifurcata), Mexican bean beetle (Epilachna varivestis): spotted cucumber beetle (Diabrotica undecimpunctata), white fringed beetle (Graphognathus leucoloma), garden fleahopper (Halticus apterus) and caterpillars of Heliothis zea. In West Africa, Ootheca mutabilis, Maruca testulalis, and Enarmonia pseudonectis have been controlled with 8 applications of a BHC/DDT mixture at 5-day intervals. Dieldrin has proved effective against Maruca testulalis and diazinon against Ophiomyia phaseoli. With effective integrated insect control, seed yield has increased 30-fold. Rust (Uromyces phaseoli), canker (Xanthomonas vignicola), wilt (Fusarium oxysporum), mildew (Erysiphe polygoni), and charcoal rot (Sclerotium bataticola) are the principal diseases. Anthracnose (Colletotrichum lindemuthianum) is damaging in humid situations, and is very important in western Africa, where rust and leaf-spot prevail. Resistance to stemrot (Phytophthora vignae) is reported. Following fungi have been recorded as attacking cowpeas: Aristastoma oenconomicum, Ascochyta pisi, Botrytis cinerea, Botryodiplodia theobromae, Cercospora canescens, C. cruenta, C. dolichi, C. vignicaulis, Chaetoseptoria vignae, C. wellmanii, Choanephora cucurbitarum, Cladosporium cladosporioides, C. vignae, Colletotrichum capsici, C. lindemuthianum, Corticium solani, Corynespora casiicola, Diaporthe phaseolorum, Diplodia natalensis, Erysiphe polygoni, Fusarium oxysporum forma tracheiphilum, (cowpea wilt, most destructive disease in California), Glomerella cingulata, G. lindemuthianum, G. vignicaulis, Helminthosporium vignae, Leptosphaerulina vignae, Macrophomina phaseoli, Microsphaera alni, Mycosphaerella pinodes, Myrothecium roridum, Nematospora phaseoli, Pellicularia filamentosa, P. koleroga, Periconia byssoides, Peronospora trifoliorum, Phoma bakeriana, P. vignae, Phyllosticta phaseolina, Phymatotrichum omnivorum, Phytophthora cactorum, P. vignae (stem rot), Pythium artotrogus, P. debaryanum, P. splendens, P. ultimum, Rhizobium japonicum, Rhizoctonia solani, Rhizopus stolonifer, Sclerotinia sclerotiorum, Sclerotium bataticola, (charcoal rot), S. rolfsii, Septoria melanophthalmi, S. vignae, S. vignicola, Sphaerotheca fuliginea, Synchytrium dolichi, Stagonospora phaseoli, Thielaviopsis basicola, Thyrospora solani, Uromyces appendiculatus, U. phaseoli, U. vignae, Verticillium alboatrum, and Woroninella dolichi. Cowpeas are infected by the following bacterial diseases: Pseudomonas phaseolicola, Ps. solanacearum, Ps. tabaci, and Xanthomonas vignicola (serious in West Africa). Virus disease of cowpeas are: alfalfa mosaic, Argentina sunflower, Brazilian tobacco streak, bushy stunt of tomato, carnation ringspot, clover mosaic, coconut wilt, cucumber mosaic, cucumber necrosis, eggplant mosaic, green mosaic, lucerne mosaic, of Crotalaria hirsuta, mosaic of Crotalaria mucronata, peach yellow bud mosaic, Pelargonium leaf curl, ringspot disease of red raspberry, subterranean clover stunt, tobacco etch, tobacco mosaic, tobacco necrosis, tomato aspermy, tomato black ring, tomato spotted wilt, cowpea mosaic (seed-borne, carried by bean-leaf beetle, Cerotoma ruficornis), white clover mosaic. Cowpeas are parasitized in Africa by Striga gesneriodes, S. lutea, and S. senegalensis. Despite nearly 75 years of efforts to find cvs resistant to root-knot nematodes (Meloidogyne spp.) and sting nematodes (Belonolaimus gracilis) the problems are still acute. Nematodes which infest cowpeas are: Belonolaimus gracilis Criconemoides spp., Ditylenchus dipsaci, Helicotylenchus cavenessi, H. pseudorobustus, Hemicycliophora arnaria, Heterodera cajani, H. glycines, H. schachtii, H. vigna, Hoplolaimus seinhorsti, Meloidogyne arenaria, M. hapla, Meloidogyne incognita, M. i. acrita, M. javanica, M. thamesi, Paratylenchus, minutus, Peltamigratus, nigeriensis, Pratylenchus brachyurus, P. coffeae, P. goodeyi, P. minyus, P. penetrans, P. pratensis, P. scribaeri, Pratylenchus thornei, P. vulnus, P. zeae, Radopholus similis, Rotylenchus renibormis, Scutellonema bradys, S. clathricaudatum, Trichodorus sp., Tylenchorhynchus brevidens, Xiphinema americanuum, X. basiri, X. ifacolum, and Zygotylenchus guevarai.


Complete list of references for Duke, Handbook of Energy Crops
Last update Friday, January 9, 1998 by aw