A total of 54 cowpea germplasm accessions were collected (Table 1) in the 16 surveyed villages (Figure 1). Among these, 45 (83%) were local varieties and 9 (17%) were commercial varieties introduced by the Federal Ministry of Agriculture of Ethiopia, the Melkassa Agricultural Research Center (MARC) and the Sirinka Agricultural Research Center (SARC). Phenotypic diversity was observed in terms of growth habit, seed color, size and shape (Table 2).
Vernacular names of cowpea
Local farmers are generators and information base for modern taxonomy since indigenous knowledge is adaptive skill of the local farmers acquired informally through interaction with the natural environment. Accordingly, cowpea has different names in different areas of northern Ethiopia by local farmers based on the multiple purposes of the crop and the unique characteristics of each landrace type (Table 2) and information on morphological diversity of the landraces is given in Table 3.
Farmers’ knowledge and utilization of cowpea
All the eighty farmers interviewed claimed to know modern agricultural production system especially in pre- and post-harvest technology. The majority of the farmers interviewed (75%) cultivated the erect type of cowpea in North Wello, Central Tigray and Waghimra zones. A reasonable number of farmers (25%) grew both the erect and prostrate or spreading types of cowpea mainly in Kalu and Bati districts. This is because in Bati and Kalu, local farmers grew cowpea when the soils are more degraded and/or where livestock are more important components of the farming system. The majority of farmers (60- 75%) preferred the erect type because they perceived that the ability to produce grains during famine season is due to its early maturing habit. Furthermore, local farmers preferred the erect types of cowpea for a variety of reasons such as high grain and straw yield, disease resistance, drought tolerance, adaptability to all types of soil, early maturity, market value, food quality, feed value and its multiple purposes. The spreading type of cowpea produced much more vegetative parts than grains and farmers mainly used this type for improving soil fertility and as animal feed. Grains, fresh vegetative parts and straw are the desired products of cowpea for all of the farmers who participated in the interview.
Based on results of the primary data, cowpea contributes to smallholders’ income and to diet as a cost-effective source of protein intake especially in Central Tigray, South Wello and Oromia Special zones found in Amhara Region. On the other hand, in Amhara Region, cowpea is mainly used for human food in the form of boiled grains (Nifro), baked as thin bread (Kita) mixed with other cereals and prepared into various sauces (Shiro Wet). The seeds are a major source of plant proteins and vitamins for humans, feed for livestock and also a source of income. The immature pods are occasionally eaten as raw vegetables in South Wello and Oromia Special zones. It is traditionally important as a source of protein especially in the leant (fasting) season of Christians in the northern part of the country. Moreover, cowpea also plays an important role in improving soil fertility in cereal crops (such as sorghum and maize) farming system when grown via intercropping and crop rotation. Informants, explanations about the use of cowpea as food, income source, forage, medicinal The best use of cowpea for a given wereda received the highest ranking value (5), while the least useful is assigned a ranking value of two (2) in this exercise.
Farming system and practices
The farmers in northern Ethiopia gave a description of the farming system and practices. They underlined that the rainy season commences in May and ends in October. They prepare the land between the months of March and May. Land preparation is mainly done by oxen ploughand weeding activity is done by manual hand-weeding and handheld hoeing. Planting commences towards the end of May, right after the first substantial rains have been received through to July and early August. By the end of November, all farmers harvested cowpea from the field.
The result of this study revealed that, cowpea is pre-dominantly grown as a sole crop (48.75%) and followed by intercropping (35%) (Figure 2).
Traditional cropping systems reported by farmers showed that farmers’ perceptions was found cowpea is mostly intercropped with cereals.
Common combinations are sorghum with cowpea and maize with cowpea using different planting methods mainly broadcasting (85%) and row planting (13.75%) (Figure 2). Furthermore, farmers produce cowpea in sandy and marginal soil conditions since the crop has the ability to with-stand drought and poor soil fertility conditions. Farmers produce this crop in their entire farms (main field, 60%; home garden, 8.75% and at borders of farm fields, 31.25%) during the rainy season except farmers from Central Tigray (Wereie Leke) where they use irrigation. The majority of farmers (60%) used their home saved seed (Figure 3) for the next growing season except in Werie Leke District where they use mostly seed obtained from agricultural office and sometimes they used their own home saved seed for the next growing season. The secondary seed source for cowpea production has been found to be local market (17.5%) (Figure 3).
Gender roles for maintaining the landrace diversity of cowpea
Traditionally, in northern Ethiopia cowpea cropping is mostly done by men including the agronomic activities such as land preparation, planting, weeding, harvesting, threshing and drying. The major responsibilities of women are preparing processed the products of cowpea in the form of local recipes. Women also participate in many activities, together with their children, to support their husbands, including in weeding and harvesting. Women are also especially involved in variety selection, post-harvest treatment (during storage), marketing of the grain and processing for animal feed.
Market value of cowpea
In addition to its food, soil improvement and forage values, cowpea has economic importance as income source; farmers often sell the grain in the local markets. The market price varied in the different districts of the study area (Figure 4). In Lasta Lalibela District, cowpea seed/grain had lower value, about Birr four per kg. Farmers in this area mostly use it as ground cover rather than for income generation. This is because farmers primarily focus on other legumes including: faba bean (Vicia faba), chickpea (Cicer aritienum) and field pea (Pisum sativum), which have higher demand than cowpea. They also mentioned some unpleasant organo-leptic characters of cowpea as a factor discouraging its consumption by people. In Werie Leke District, cowpea has higher market price (Birr 17.5 per kg) than in other districts. This is because, in Werie Leke there is scarcity of livestock forage and the local farmers grew cowpea via intercropping with maize for livestock feed and for marketing.
The cowpea value chain consists of local exchanges and markets that ensure a movement of grain from producers to consumers. Therefore, exchange begins with the production of cowpea by small scale farmers. In northern Ethiopia, farmers typically sell their cowpea grains directly to consumers or some times to rural assemblers, who in turn sell it directly to consumers and bigger merchants.
Production constraints
In Northern Ethiopia, small holder farmers are facing different constraints on cropping, storage and con-sumption of cowpea including storage pests, field insects, parasitic weeds and diseases. However, farmers were unable to identify the names of insect pests and diseases. Nonetheless, according to the descriptions they provided aphids and pod borers were the most important insect pest problems for farmers. The primary insect pest causing losses to stored cowpea in northern Ethiopia according to the local farmers is storage weevil (Callosobruchus maculatus) locally called Nekez. Another menace is parasitic plant, locally called Akanchira, a parasitic weed typically found in the study area causing yield losses as a root parasite.
DISCUSSION
Cowpea landrace diversity in northern Ethiopia
Landraces, also called farmers’ varieties are the result of several years of natural and artificial selections by farmers for better adaptation to local growing conditions (Hegde and Mishra, 2009). Cowpea landraces collected from northern Ethiopia did not show much variation for plant growth pattern and growth habit. All local farmers grew determinate types with prostrate to erect growth habit. Such types are preferred by farmers because of their better performance under marginal conditions of rain fed environments where cowpea is commonly grown. Thulin (1989) reported that Vigna unguiculata subsp. Sesquipedalis and subsp. dekindtiana are mainly cultivated in northern Ethiopia. In the present study, landraces belonging to Vigna unguiculata subsp. unguiculata and Vigna unguiculata subsp. cylindrica were found under cultivation as components of different cropping systems under marginal rain fed conditions. The local landraces (83%) are more popular than the released commercial varieties because of farmers’ preference owing mainly to their multi-purpose nature, organoleptic characters and higher market prices. The majority of landraces collected from Bati and Kalu districts of Amhara Region belonged to Vigna unguiculata subsp. unguiculata farmers’ variety Jergadie having prostrate (climbing) nature with higher vegetative growth and long pods in contrast to the erect type of cowpea. The collected landrace accessions were found both in mixed and uniform seed colors. Similar results were reported by Sariah (2010) where landrace accessions are mostly found both in mixed and uniform seed colors. From it that they grow cowpea for home consumption, livestock feed, income source and improving soil fertility. Thus, almost all collections from each district were found to be uniform in seed color except in some areas where accessions with mixed seed colors were found ranging from white to black, with cream and light red colors dominating mainly in Bati and Kalu districts and these were described as large seeded Jergadie. This landrace type is mainly produced in Tanqua Abergelle and Bati as a major crop.
Cowpea is an important component of diets in northern Ethiopia, thus widely cultivated in Central Tigray (Tanqua Abergelle, Kola Temben and Werie Leke), Waghimra (Abergelle), South Wello (Kalu) and Oromiya Special zones (Bati). This is not the case in North Wello Zone (Lasta Lalibela), farmers said cowpea is predominantly grown for income generation, contingency of land use (ground cover) and sometimes for food. The reverse is true for Central Tigray local farmers where cowpea has an equal value with sorghum in terms of price value and major uses for home consumption primarily grown for food, income generation and forage.
Farmers’ knowledge and perceptions
Cowpea is a versatile food crop that contributes to food culture in many parts of Africa (Timko and Singh, 2008) and referred to as the "hungry-season crop" given that it is the first crop to be harvested before the cereal crops are ready (Carlos, 2004). The same is true for Waghimra and Central Tigray zones where the crop is used as hungry-season crop and obviously known and grown by all farmers. This reflects the importance of cowpea in the day-to-day life of farmers in northern Ethiopia, which might probably be due to the fact that cowpea has the ability to withstand the existing dry conditions in the study areas. In every growing season, almost all farmers grow cowpea by intercropping with sorghum and maize except in Sekota and Lasta Lalibela districts where the farmers mainly use sole cropping system at their main and boarder farm fields as minor cropping. Both climbing and erect types of cowpea were grown in northern Ethiopia to exploit the advantages provided by each type. As described by Carlos (2004), the fast growth and spreading habit of traditional cowpea farmers’ varieties suppress weeds, and soil nitrogen is increased which improves cereal growth. Farmers’ responses on the selection criteria were based on the crop’s multipurpose nature being used for human consumption, animal feed, income source and improving soil fertility. Cowpea also contributes to the sustainability of cropping systems and soil fertility improvement on marginal lands through nitrogen fixation, provision of ground cover and plant residues, which minimize erosion and subsequent land deterioration.
Crop uses and purpose of production
As indicated by Westphal (1974), Thulin (1989) and Gbaguidi et al. (2013), vernacular names traditionally attributed to crop varieties vary more often across administrative districts and villages even sometimes between farmers within a single village. Similar results were reported by Singh et al. (2003) and Timko and Singh (2008). As reported by Phillips et al. (2003) and Timko et al. (2008) cowpea is a multi-purpose crop and it is used for food, forage, income generation and improving soil fertility as asserted by all respondents of the present study. In addition, Megersa et al. (2013) reported that, cowpea is traditionally used by smashing and rubbing on affected part of body to treat the disease known as Tinea Corporis. The present study results did not indicate the use of cowpea as a medicine. Almost all parts of the crop such as seeds, pods, leaves/stems and straw are used for various purposes as reported by Singh et al. (2003); Pottorff et al. (2012) and the present study. As reported by Carlos (2004), in southern Africa, cowpea is grown primarily for fodder, although it is also used for grain production, green manure, and weed control in forestry plantations and as a ground cover to prevent soil erosion. In this study, cowpea uses varied considerably between regions and some uses reported from other countries were not recorded in northern Ethiopia. As reported by Timko et al. (2007), the tender green leaves are an important food source in Africa and are prepared as a pot herb, like spinach. Cowpea green leaves and immature pods are consumed as green vegetables in southern and eastern Ethiopia (Westphal, 1974). Immature green pods are used in the same way as snap beans, often being mixed with cooked dry cowpea or with other foods. The consumption of nearly mature cowpea grains shelled and boiled as a fresh vegetable reported in other parts of Africa is recorded in the present study in Ethiopia. The study results further showed that the seed is a highly valued part of the crop for home consumption in the form of Nifro, Kita and Wet. Sometimes, the green mature pods were eaten by children in Bati and Kalu districts. As stated by Singh and Tarawali (1997), in northern Ethiopia cowpea foliage is an important source of high-quality hay for livestock feed.
Cropping systems and management practices
As reported by Blade et al. (1997) and Timko et al. (2007), cowpea is usually grown as an intercrop with sorghum (Sorghum bicolor (L.) Moench) and less frequently as a sole crop or intercropped with maize (Zea mays L.), cassava (Manihot esculenta Crantz), or cotton (Gossypium sp.). In the present study, cowpea is mainly grown as a rain fed crop and sorghum is the major cereal crop with which cowpea is intercropped (95%) in all surveyed areas, except in Werie Leke District where maize is the major cereal in which cowpea is intercropped (5%) along irrigation channels. Carlos (2004) and Dugje et al. (2009) described a similar intercropping system in West and Central Africa under similar semi-arid conditions, where cowpea was also intercropped with cereal crops (maize and sorghum) with the recommended spacing of 75 cm x 50 cm. Dugje et al. (2009) and AFF (2011) reported that fertilizer application in cowpea production depends on anticipated yield and soil fertility. As a legume, cowpea does not require much nitrogen because of the symbiotic nitrogen fixation. Based on the results, the majority of farmers (60%) indicated that they never used fertilizer and/or chemicals in the surveyed areas especially in Tanqua Abergelle, Abergelle, Sekota and Lasta Lalibela districts. On the other hand, reasonable number of the farmers (40%) used compost to improve soil fertility and chemical pesticides for plant protection in Bati, Kalu, Kola Temben and Werie Leke districts.
Seed supply, selection and storage
The reliance of local farmers mainly on sources of home saved seed and exchanging with their neighbors is a good support in maintaining and conserving the distinct types, but at the same time there is little driving force to create new types and maintain a high level of diversity (Munisse et al., 2011). The present study result also showed that, the majority of farmers relied on their own home saved seeds, buying from local market, exchanging with neighbors or relatives, buying from agricultural office (only landraces) and sourced from both home saved and agricultural office. The most important farmers’ criteria for selection are tolerance to drought, good taste, high grain yield, early maturity, feed value and market value of grain. For example, some farmers in Bati and Kalu districts preferred cowpea landrace having the climbing habit (Jergadie) due to its leafy nature that improves soil fertility via nitrogen fixation and livestock feed value as compared to cowpea types with erect growth nature (Kimite and Chekele).
Cowpea is highly vulnerable to insect attacks and damage due to storage pests. There are published data (Carlos, 2004; Dugje et al., 2009) providing evidence that insect pests cause devastating losses in cowpea yields and weevils (post-harvest pest) can destroy a granary full of cowpea grains within two or three months. In northern Ethiopia, some farmers stored the seed with special treatment using chemicals (malatine), botanicals and ash for the next growing season to escape storage pest problem. As a result, all farmers reported that storage pests are the major causes of post-harvest losses. As reported by Dugje et al. (2009), insect pests are major constraints to cowpea production in West Africa and damage by insect pests on cowpea can be as high as 80–100% if not effectively controlled. The most important storage pest of cowpea is the weevil (Callosobruchus maculatus) and severe infestation can lead to total grain loss in storage (Carlos, 2004; Dugje et al., 2009; Sariah, 2010). The storage life of cowpea depends on its moisture content before storage; and the lower it is the better the quality of seeds for storage (AFF, 2011). In developed countries, one alternative is the use of cold storage and that exposure to minus 180C during 6 to 24 h
reduced pest numbers by more than 99% (Carlos, 2004).
Qualitative and quantitative traits
Earlier studies on cowpea showed that morphological traits were of great importance to distinguish genetic variability. As in previous studies (Hegde and Mishra, 2009; Sariah, 2010; Gbaguidi et al., 2013), this study also found that morphological traits (quantitative and qualitative) are valuable tools for cowpea genetic diversity studies. For example, some of the morphological traits such as growth habit, terminal leaflet length, terminal leaflet width, seed length, twining tendency, terminal leaflet shape, pod length, number of seeds per pod and seed shape had the uses for morphological identification and characterization. The results showed that landraces collected in Bati and Lasta Lalibela locally called Chekele and Kimite were similar. Similarities of some characters were also observed between Jergadie on the one hand and Kimite and Chekele on the other. As for the qualitative traits, the existence of genetic diversity among the collections for most of the morphological traits studied, Chekele and Kimite were more varied than Jergadie. A high level of similarity was also observed among the collection of Chekele and Kimite for most of the traits studied.
