Considering all the protein sources that might possibly help Africa’s malnourished millions, none seems more promising or more practical than grain legumes. Legume seeds famously deliver the amino acids needed to grow or repair protein-based tissues such as brain, nerve, and muscle, as well as to construct the enzymes and proteinaceous hormones necessary for normal life functions. As tools for balancing nutrition they can have a powerful overall effect among the impoverished masses. By providing protein (not to mention vitamins, minerals, and energy), they make main foods—notably, the bulky staples, such as rice, maize, cassava—work better in the body. In this sense, they help increase the bioavailability of other nutrients. Grain legumes, in other words, act like nutritional cogwheels, making everything else go round and round in proper order.
Luckily for the particular malnourished millions in Africa there are grain legumes for almost every local soil and climatic zone.1 In the specific areas most at risk of hunger and malnutrition, though, the leading locally domesticated candidate is cowpea. Although hardly known in global terms, cowpea constitutes Subsaharan Africa’s most widely planted native legume. At present it is the second most important grain legume continent-wide; only peanut—a native of the Americas—occupies more African farmland. West Africa’s farmers alone grow cowpea on an estimated 6 million hectares. More than 95 percent of the world crop comes from that area; Nigeria, the biggest producer, grows an amount variously estimated at several million tons a year.
Given quantities like that, one might question this species’ inclusion in a “lost crops” book. But the cowpea’s widespread occurrence and importance in the lives of the most malnourished makes this particular grain legume critical for lifting the nutritional baseline for many societies and many levels of those societies. In a sense, it is a fulcrum for leveraging Africa’s basic nutrition. For all that, though, it is now not being intensively used to leverage the continental wellbeing. In this special sense, then, cowpea is being “lost,” at least to future progress.
Regarded strictly from a botanical perspective, this crop seems strong enough to help lift Africa’s food quality in the 21st century. The species is exceptionally rich in useful genetic diversity. It produces several different tasty foods. The plant is deep rooted, vigorous in growth, and reliable in production. It is both drought-tolerant and adapted to poor soils. The seeds are exceptionally nutritious, possessing protein (up to 24 percent in dry seeds) and a trove of other essential nutrients. As a dietary component, it complements the otherwise unbalanced diets the poorest sectors are forced to stomach. And, perhaps because of its African birth it beats out other legumes for performance on a variety of soils and an adversity of conditions found across this multiform continent. Indeed, cowpea has been called “a nearly perfect match for the African soil, weather, and people.”
This crop originated as an inconspicuous little creeper among the rocks of the dusty southern Sahel and the bone-dry upper rim of central Africa. Africans living there thousands of years ago saved the best seeds they could
find and ultimately brought cowpea entirely under their care. Today, inter-pollinated descendants of their creations grow on millions of smallholder farms in a sweeping arc from Senegal eastward to Sudan and Somalia and southward to Zimbabwe, Botswana, and Mozambique.
In that great sweep, covering half of Subsaharan Africa, two hundred million children, women, and men live off the plant—consuming the grain daily whenever supplies make that possible. Widely appreciated by the poor, cowpea is not only rich in protein but in digestible carbohydrate too. Its energy content nearly equals that of cereal grains. In addition, the seed is low in antinutritional factors. And the seeds of select strains cook fast, an important consideration where fuelwood is scarce and expensive, as it is in that vast parched crescent of concern between Senegal and Mozambique.
One of the more remarkable and valuable things about this species is that certain of its cultivars mature with as little as 300 mm of rainfall. This makes it the grain legume of choice for the Sahelian zone and its contiguous savannas, both of which are population-dense, hungry, and vulnerable to outbreaks of malnutrition and mass misery.
No less remarkable is cowpea’s value to the environment. The deep roots help stabilize the soil and the plant’s shade and dense cover helps protect the ground and preserve moisture. Both these traits are of particular importance in the dry zones, where moisture is at a premium, soil is fragile, and wind a dirt-scouring demon. Like other legumes, cowpea fixes atmospheric nitrogen, thus lifting the nitrogen content in the land around it. It is often intercropped with sorghum, millet, or maize, as much to foster their good health as to furnish its own beans.
Beyond its value to the malnourished, this is a crop of high potential for rural development. Although Nigeria produces it by the millions of tons, production in East, Central and Southern Africa is still very low.
Because of its combination of benefits, cowpea is perhaps the most vital of all Africa’s native vegetables. It seems thus likely that it has the best potential for boosting the nutrition of the greatest number of needful Africans. Even a small lift in cowpea performance can have a significant spillover benefiting millions2 .
Humid Areas Prospects here seem moderate, but could rise quickly. In wet areas, cowpea falls victim to hosts of pests and diseases. Nonetheless,
types that flourish in moist savannas are coming available, and those could provide a solid foundation to build a better future.
Dry Areas Excellent. Cowpeas are more drought-tolerant than peanut or maize (but not more than millet), and are vitally important in the West African savanna, where the bulk of the crop is produced.
Upland Areas Variable, depending on location, but no less promising for all that. Most cowpea varieties do not withstand cold conditions that well. They either fail to germinate, grow slowly, or do not flower at all. Production in the highlands during hot, dry seasons can be very high however.
The dried seeds are eaten in parts of the Asian and American tropics and subtropics. They are, for example, well known in India, Brazil, the Caribbean, and United States, known there as blackeye peas. As better cultivars come available, cowpeas could become even more important in the dryland tropics. According to reports, cowpea is taking off in Thailand. China and a number of other nations seem ideal targets for future expansion. There, cowpea could contribute inexpensive protein to many predominantly starchy diets.
Unlike other legumes, cowpea can be consumed at different stages in its development: fresh green leaves, dry leaves, green pods, green beans, or dry grain. The most popular—or at least most common—is the last.
Pods The immature seeds and the immature seed pods are boiled and eaten as a vegetable. This is a very special and highly promising usage. Indeed, we have dedicated a separate chapter to a cowpea variant called long bean, which developed far from Africa’s shores and now deserves better back home.
Seeds Traditional West African cooking has found a variety of uses for this food. There, most cowpeas are cooked with vegetables, spices, and palm oil to produce a thick soup that accompanies the basic staple, notably cassava, yam, or plantain. The seeds are also decorticated, ground into a flour, mixed with chopped onion and spices, and pressed into cakes that are either deep-fried (akara balls) or steamed (moin-moin). Some are ground or crushed into meal that is used in buns, fritters, and sauces. Cowpea meal is also boiled, mashed, and served in puddings, porridges, and soups. The seeds are commonly boiled with maize, eaten as porridge, or even boiled in
their pods. Alternatively they may be steamed or fried to make a paste or sauce that is often eaten with ugali or other thick starchy staple. Canned cowpea has rapidly become popular in the Zimbabwean markets.
Forage In most locations cowpea is treated as a dual-purpose crop, in which one of the two products is hay. In years of poor rainfall, when stockfeed is scarce, it can be worth far more than the seeds. Livestock, particularly cattle, thrive on the stems and leaves left once the seeds have been harvested. Those haulms can also be dried, bundled, and stored away for the dry months when little else is around to keep domestic creatures happy and healthy.
Green Manure Cowpea fixes nitrogen efficiently, with amounts of up to 70 kilograms per hectare per year added to the soil. This makes it a useful living mulch for reconstructing broken-down land.
Other Uses Occasionally, cowpeas are roasted, ground, and served as a coffee substitute. In the United States, the green seeds are sometimes roasted to produce peanut-like snack foods.
Dried cowpea seed is exceptionally nutritious, with up to 24-percent protein and 2 percent oil, with the remainder being carbohydrate, minerals, and lesser nutrients. This combination means that cowpea packs solid nutrition. On top of that it is palatable and relatively free of the kind of metabolites that suppress soybean’s food value.
The protein itself is of good nutritional quality, consisting of 90 percent water-insoluble globulins and 10 percent water-soluble albumins. There is considerable genetic variation in amino-acid content, but lysine seems always in good supply. Indeed, that is one of the greatest features: combined with cereals in the diet, cowpea makes up for the lysine-poor cereals and roots. As in other grain legumes, methionine, cystine and tryptophan are deficient.
Most of the crop is grown for home consumption. A portion comes from kitchen gardens or village compounds, but most cowpeas are grown in the main production fields as an intercrop with cereals and/or other crops such as tomato, okra, peppers, and eggplant.3 In both dry- and moist savannas the cereal is millet, sorghum, or maize. This combination of legume and cereal
makes for a complex, dynamic, hard-to-manage system, but it meets the critical needs of growers, who above all must produce the family’s yearlong subsistence. When the first rains appear, they typically plant the cereal together with an early-maturing cowpea (which is often destined for fodder rather than food). Once the cereal is growing well, a second cowpea crop is sown among the strengthening stems—a strategy used notably in the drier areas to avoid early season drought damage. Clambering types are considered best because they climb over and crush any weeds that try to interfere. Once the creeping cowpeas start moving out weeds are no worry.
Traditional cowpea types in the Sahel and savannas are attuned to subtle differences in the length of day. As if reading a calendar, they burst into flower just as the rainy season ends and the long period of dryness begins. That is a clever way to avoid devastation from pests and diseases, because vulnerable parts of the plant emerge after enemies have subsided. It is, however, a risky strategy because it puts the plants at the mercy of drought and blistering heat. Also, in this seemingly synergistic cultivation system, the crops compete for each other’s light, nutrients, and moisture, which limits the capabilities of both. It the rains disappear too quickly, as occurs too often, the competition between cereal and cowpea can have catastrophic consequences on the quantity of food the family gets to eat that year.4
HARVESTING AND HANDLING
Depending on cultivar and climate, cowpeas may take as few as 60 or as many as 240 days to mature their seeds. Harvesting is complicated by the prolonged and uneven ripening characterizing many types. The pods must be harvested as soon as they mature because they shatter easily and after a few days wantonly scatter the seeds on the ground. Further, seeds that get damp from rain or excessive humidity before being harvested start sprouting inside the pods while yet on the plants.
Under conditions of subsistence agriculture, the average yield of dry seed normally ranges between 100 and 300 kg per hectare. Compared to yields of modern soybean (3,000 kg per hectare and up), peanut (2,000), or even cowpea grown on experiment stations and in countries such as India (at least 2,000), this is an appalling level Much of the difference is due to the fact that cowpea occupies only a small part of each hectare of the mixed cropping system. But some is due to the particular types used by Africa’s subsistence farmers. Those traditionally selected plants may be very clever at dodging their enemies but from a productivity standpoint, they aren’t very good.
Whatever the climate, locale, or cultivation method, insects are the major constraint. In the lowland tropics the effect can be so devastating that overcoming them could send grain production soaring 20 fold or more, according to literature reports. But it is not an easy task. Africa has at least 15 major and more than 100 minor insect pests that challenge cowpea.
By comparison with the insect onslaught, diseases are less troublesome, but that’s not saying much. Fungi sometimes cause terrible damage, especially in the wetter areas. Devastating attacks are not unknown in the drier areas as well.
Even when the harvest is in hand, the farmer’s fight for her food is far from over. Certain insects make their living on cowpeas in storage. Cowpea weevil and bruchid beetle are the major threat here. They begin infesting the plant in the field, but really capitalize when the seeds are crammed together in a grain bin or silo. There in weevil heaven each female produces 20 ravenous larvae every 3 or 4 weeks, so within a few months nearly every seed has a neat hole drilled in its side. And within six months little that is edible remains. Food prepared with even partially infested grain tastes bad, and selling seed exhibiting even a few of the telltale beetle holes is difficult. In Nigeria it has been estimated that some 30,000 tons of cowpea grain are lost annually, most of it during storage.
Perhaps the quickest way to get cowpeas in Africa producing up to their fullest potential is to activate programs in Asia and the Americas. A global effort, involving say 20 nations from China to Chile and Australia to Arabia, could change the whole dynamic. This is not such an unlikely notion. Almost all nations face a long-term need for more drought-tolerant and more nutritious crops. In fact, cowpea is already rising slowly as a global resource. From this worldwide movement, the humanitarian benefit to the continent that produced the plant in the first place could be the greatest of all. But by developing new methods of production, new gene combinations, and new basic knowledge, all countries would be benefiting their own farmers and citizenry while building new momentum for a largely forgotten global crop.
So far, the main thrust of research for the cowpea-zone of Africa has been to induce farmers to grow the crop in pure stands rather than mixed with cereals. This is clearly a good thing if one considers only cowpea. But the subsistence farmers depend on the combination, and the switch to a single crop can reduce overall productivity. For small-scale farmers it may also weaken their security by taking away millet or sorghum, their most dependable crops. Nonetheless, for farmers with surplus land and labor, pure-stand cowpea makes an attractive cash crop. Researchers involved in it are not wasting their time. Some observers claim that such commercial production will never benefit enough cowpea growers to justify the research, but they could well be wrong. Cowpea has the potential to be a tool the
millions of impoverished farmers employ to lift themselves from poverty to prosperity. Given a chance to make a good profit they may embrace commercial cowpea with gusto.
Demand for cowpea fodder far exceeds current production, and a ready market exists for cowpea haulms, which can command nearly the same price as cowpea grain. Some emphasis should be put on this usage, even though feeding animals may seem a roundabout means for getting food to people. In this arena, cultivars primarily for fodder or green manure merit exploration.
Commercial Promotion The status of cowpea could be greatly lifted by stimulating demand through a sophisticated marketing campaign. Cowpea lends itself to this. It is a delicious food; it is grown, at least in Africa, organically without chemical inputs; it is a product that supports the poorest of African farmers; and it allows them to make a living from a hostile environment. Such a campaign could be targeted at local, regional, and international consumers (such as in Europe and North America). With bigger markets, research stations will fund more research, the private sector will finance product development, and the farmers of Africa will grow more cowpea and make a better living.
Food Technology The seeds have a relatively high protein content and it has been suggested that this could be extracted to prepare protein concentrates for the food manufacturing, textile and paper industries. In this regard, cowpea might end up Africa’s counterpart of Asia’s soybean…one of the world’s top crops.
Combating the cowpea’s enemies in storage is far from easy. Some progress is being made, however. In Nigeria it is recognized that harvesting promptly reduces the initial damage and that storage in the pod affords a degree of protection. Fumigation is effective, but difficult for small farmers to perform efficiently and safely. The hermetic storage of cowpeas in small granaries, silos and pits is being developed in Nigeria, where a very encouraging development has been the use of plastic liners in traditional dried-earth granaries. Investigations in Senegal have shown that cowpeas may be stored satisfactorily for up to a year in plastic sacks, albeit using as a fumigant the very toxic carbon tetrachloride. In India, the leaves of the neem tree are added to bins containing grains such as cowpea. Neem grows well in the cowpea zone of Africa, and this is another likely means for securing safe storage.5 Cowpeas treated with palm, peanut or coconut oils are reported safe against insect infestation for as long as 6 months, but that affects the taste of some foods, and the seeds may lose their viability. Progress has been made, too, with breeding or selecting plants whose seeds resist bruchids, but
these seeds tend to be dark and thick-skinned, and that can make people resistant too.
Horticultural Development A dominant factor limiting seed yields is depredation by insects feeding off plants. Thrips are often most important, and these flower-eating scourges are so efficient that often no blossoms remain to form pods. Also slashing yields are pod borers that ream their way inside the pod and consume the soft contents before any seeds mature.
Controlling these pests seems a good topic for the methods and principles of integrated pest management. Already, it is known that destroying all diseased plant material in the field, employing mixed cropping system to reduce pest load, as well as rotating crops, helps lower insect depredations.
Fast-maturing cowpea types minimize the exposure to diseases (not to mention pests and even harsh weather), and are very desirable and important. However, the most effective long-term solution to the disease problems lies in the development of resistant cultivars. Research has already attempted this, but without producing breakthroughs big enough to cause the millions of subsistence farmers to switch.
The process of mixed-stand cultivation has fallen in and out of fashion with researchers in the region since the 1970s, without significant technologies resulting. Yet this is how African farmers grow cowpea, and it is begging for better understanding and support. The field layout is one feature for consideration.6 The genetics of the plants is another. Farmers committed to the dual-cropping system with cereals and cowpea need daylength sensitive types that produce a flush of flowers after the cereal harvest. Breeding for every latitude and local preference would be a logistical and financial nightmare. But research aimed at improving plants for the main growing regions is well justified.
On a slightly different note, in Guinea cowpeas are being experimented with as a fallow crop in lowland rice fields. Initial results in 1999-2000 were said to be very promising with good yields, high levels of farmer interest, and noted contributions to soil fertility (which were the reasons for initiating the trials). This may introduce cowpea to a completely new, high potential environment, where it can make important contributions.
Storage The problem of insect infestation cannot be over-emphasized. One of our reviewers writes: “In Zimbabwe, we have tremendous difficulties with bruchids and must make sure crop gets from farmer to warehouse where it can be fumigated as soon as possible. It makes on farm storage and factory storage problematic.” In this regard, an appropriate technology was developed at Michigan State University in the 1980s. Researchers discovered that simply turning the sack in which beans are stored is enough to virtually eliminate weevil damage. Weevils require upwards of 24 hrs to bore into a grain. During this time they need to brace themselves against neighboring grains in order to drill into their target. Turning the sack end-over-end 2-3 times once a day causes the weevils to loose their place, and require them to start afresh. After several aborted attempts the weevils die without having laid a single egg!7
Botanical Name Vigna unguiculata (L.) Walp.
Synonyms Vigna sinensis, Vigna sesquipedalis
Family Leguminosae. Subfamily: Papilionoideae (Faboideae)—Pea family
Common Names (for grain types)
Arabic: Lupia (in Sudan)
English: cowpea, blackeye pea, blackeye bean, marble pea
Spanish: chicharo de vaca
Ethiopia: adanguari, nori
Nigeria: agwa, akidiani
Uganda: amuli, boo-ngor, omugobe, boo (in Acholi and Luo)
Zambia: ilanda, nyabo (in Tonga language)
Zimbabwe: nyemba (Shona) ndlubu (Ndebele, Zulu)
Botswana: dinawa, Nyeru or Dinawa (in Setswana)
Kenya: boo (in Luo language); kunde (in Swahili); thoroko (in Kikuyu)
Portuguese: ervihia de vaca
India: barbata, charla, Nindu pea, paythenkai, thattapayru (Tamil)
Sri Lanka: me-karak
Malaysia: kachang bol
Philippines: karkala, kibal
Thailand: tonkin pea
Mauritius: voehme (in Mauritian Creole)
Tanzania: kunde (in Swahili); nkunde (in Nyiha)
Lesotho: lLinaoa (in Sesotho)
South Africa: dinawa (in Northern Sotho)
Malawi: nkunde (in Tumbuka); khobwe (in Chewa)
Swaziland: tinhlumayi (in Siswati)
Seychelles: brenm (in Seychellois Creole)
Namibia: omakunde, olunya (white with black eye), omandume or ongoli (mixed black, brown, purple) (in Oshiwambo language, Ovambo tribe)
Cowpeas are an annual crop. There are many different types, varying in growth habit from erect or semi-upright to spreading and climbing. They range in height (or length) from 20 to 200 cm, the latter being the climbing ones. The species is largely self-pollinating, but up to 2 percent outcrossing has been reported.8 Flowers may be purple, pink, white, blue, or yellow. Pods tend to be long, smooth, cylindrical, and somewhat constricted between the seeds. Between 8 and 20 seeds occur per pod. They are globular to kidney-shaped, 5-12 mm long, smooth or wrinkled, and ranging in color from white, cream, or yellow to red, brown, or black, while some are speckled or blotched. The seeds are characteristic in having a marked white hilum surrounded by a dark ring. The most commonly grown are the white types or those with a black mark around the hilum, the latter being called
‘black-eyed.’ Pods of most varieties hang downwards but in some they point sideways or upwards.
Within Africa The leading cowpea growing countries are Nigeria and Niger, but the land area planted to the crop is substantial in Senegal, Mauritania, Mali, Burkina Faso, Côte D’Ivoire, Ghana, Benin, Togo, Chad, Cameroon, Central African Republic, Congo, Uganda, Tanzania, Sudan, Ethiopia, Kenya, Angola, Somalia, Zambia, Mozambique, Zimbabwe, Botswana, Namibia, South Africa, and Madagascar. Of total world production, about 80 percent comes from Nigeria, 80 percent of whose harvest comes from the parched northern states of Kano, Sokoto, and Borno.
Beyond Africa Cowpea is an important crop in some tropical American countries, especially in northeastern Brazil. In the USA, where “black eye peas” is a heritage crop, there is considerable cowpea production; California, Texas, Arkansas and the southeastern states yielding 20,000 tons a year. Most production is for the dry grain, but in the southeast it is grown primarily to serve the fresh and frozen market. It is also grown on a limited scale in the Mediterranean region and Australia. In India, the crop is grown especially for the immature pods and beans, fodder, and green manure. Indians enjoy cowpeas either boiled whole or mashed into dhal.
Because of the large number of distinct forms and the fact that hybridization is readily achieved, there is much confusion and disagreement on the proper classification of the vast, spreading genepool of the crop called cowpea. All the forms are interfertile, can be crossed freely, and free gene flow is possible, and it now seems widely accepted that there should be no distinction at the species level. In other words, there is a single species Vigna unguiculata, with the other names as synonyms (and, often, subspecies). It seems probable that some, if not all, of the cultivated forms are in fact hybrids.
Nonetheless, the vast diversity selected by humans over thousands of years in this species has scarcely been tapped by modern science. There are myriad forms that could provide rewarding work to aspiring plant champions, and great benefits to humanity. One of these, the long bean (subspecies sesquipedalis), is highlighted in Chapter 12. A related species of Vigna (a genus of about 150 species) is the bambara bean (V. subterranea), discussed in Chapter 2.