Chapters 5.35

5.35 -A Sustainable Innovation to Preserve Cowpea Crops

Jacob Koole , University of Guelph, Canada

Suggested citation for this chapter.

Koole,J. (2022) A Sustainable Innovation to Preserve Cowpea Crops, In Farmpedia, The Encyclopedia for Small Scale Farmers. Editor, M.N. Raizada, University of Guelph, Canada. http://www.farmpedia.org

Origin of the Cowpea

Cowpea (Vigna unguiculata) is an antique legume that originated in western Africa roughly around 3000 B.C.E (Smith, 2005). Though widely produced in Ethiopia, cowpea is grown worldwide in countries such as Brazil, the United States, and the majority of Asia (Gómez, 2004). Cowpea demonstrates remarkable drought tolerance because of its tendency to form a deep taproot that can comfortably grow in dry soils (Gómez, 2004). The deep taproot creates potential to mitigate drought tolerance associated with various climates. The cowpea plant itself spreads, covering much of the ground (Gómez, 2004), resulting in weed suppression. The plant varies by variety but typically has climbing vines and sporadic leaves (Gómez, 2004). An interesting element about the cowpea is the self pollinating flowers that sprout in clusters during blooming season (Gómez, 2004). These flowers can be a variety of colours such as purple, white, dirty yellow, blue or pink. This plant is beneficial not only to people and animals that consume it but to pollinating insects as well (Gómez, 2004).

Cowpea Sub-Species and Seedbanks

As mentioned earlier, there are many landraces and varieties of cowpea. These seeds differ as a result of habitat, growth, disease resistance, colour, and the size of seed (Gómez, 2004). Cowpeas are adaptable to local environments and needs, resulting in many diverse seeds sold in the marketplace. Subspecies such as the black eyed peas, catjang, and yardlong beans are all high quality legumes that contribute nutritional benefits to different regions of the world (Gómez, 2004). These particular seeds can be accessed by local seed banks at affordable prices for large and small scale farmers where available. Three major international CGIAR institutes breed cowpea and possess seed banks. The World Vegetable Center (AVRDC), International Institute of Tropical Agriculture (IITA), and International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) all breed cowpea and posses seed banks. All organizations provide helpful information for farmers to either acquire cowpea and distribute. Methods of preparation, harvesting, and marketing are all contributions these organizations share with farmers. Seeds of cowpea can be requested online using the links at the bottom of this chapter.

Cowpea Cultivation

Grown worldwide, the cowpea is adaptable to different growing conditions including semi-arid regions and dry savannas (USDA, 2012) and can grow in as little as 300 mm of rainfall (Gómez, 2004). The growing season is typically between 100 to 120 days depending on irrigation/rainfall (Gómez, 2004). It is best to plant the seed 1 to 2 inches below the soil in early summer at 50 lbs per acre, or minimally 30 lbs per acre (USDA, 2012). Soils in the Western Africa regions are low in nitrogen and phosphorus, so it is critical that fertilizer/manure management is followed to obtain high yielding crops (Bationo, 2003). The most effective way to prepare the soil is to plow after the first rain; the deep taproot needs loose soil (Ishikawa, 2013). The best fertilizer to incorporate into the soil is either ripened organic manure or chemical fertilizer, both of which must be spread evenly through the soil (Ishikawa, 2013). Cowpea is heavily reliant on phosphate, and a healthy crop typically requires a pH range of 3.95-7.6 (Bationo, 2003). Symbiotic bacteria living inside cowpea root nodules produce fixed nitrogen, reducing its nitrogen fertilizer requirement though other nutrients are required (USDA, 2012). Though inoculation with nitrogen-fixing rhizobia bacteria has been shown to be effective, the cowpea can nodulate in an array of soils (USDA, 2012). In nutrient-deficient soils, cowpea requires starter nitrogen to develop the nodules before nitrogen fixation can begin (Ishikawa, 2013). Farmers must find a way to incorporate nitrogen into the dry soil in order for the cowpea to grow. A fairly inexpensive solution to this challenge is the use of compost if one owns livestock (Ishikawa, 2013). Covering the collected compost with black vinyl will preserve the nutrients stored inside (Ishikawa, 2013). Synthetic manure can also be purchased but can be more costly. Cowpea can be interseeded with sorghum and wheat, providing nitrogen benefits to those crops (USDA, 2012). After roughly 8 weeks the deep taproot is formed and flowering follows (USDA, 2012).

Harvesting and Storage

Harvesting generally takes place 16 to 17 days after bloom (Gómez, 2004). Farmers know when it is time to harvest when the seed pods have matured and flowers are blooming (USDA, 2012). The three main ways to harvest is by hand, mechanized, and direct harvesting (Gómez, 2004). The most efficient method when harvesting by hand is threshing (Gómez, 2004). Threshing is separating the seeds from the plant by beating it on the ground, many rural farmers use this method (Ishikawa, 2013). A mechanized threshing machine exists where this complex machine is designed to cut the plant out of the ground using horizontal blades to be threshed later (Gómez, 2004).

Direct harvesting, which is common in wealthy nations, and uses combines and other heavy agricultural machinery (Gómez, 2004), is not available for cowpea smallholder farmers as machines are very expensive. Cowpeas are fragile, so harvesting must be done cautiously as a broken seed can result in stunted growth and loss in market value (Gómez, 2004). In order to successfully maintain seed viability, the grain must be dried to around 12% moisture or less (Gómez, 2004). Producers will modify their storage methods to meet certain market specifications.

Cowpea Nutrition

The cowpea is of significant importance to the millions of people in West and Central Africa (Gómez, 2004). This crop is heavily relied on by people for food, feeding livestock, and income. This legume is high in protein. making it very sustainable for humans and animals (Gómez, 2004). Cowpea grain can be dried up and stored away giving consistent nutrition for families along with feeder for livestock (Gómez, 2004). The high protein content comes from the fact that cowpea is a nitrogen fixing legume. The crop’s decomposing roots/shoots, also rich in organic nitrogen, benefits soil fertility and helps future crops subsequently planted in rotation (Gómez, 2004). Raw cowpea seeds provide high nutritional value essential for a healthy diet. Many popular recipes use cowpea as a key ingredient to the dish. Collard and black eyed pea soup, Nigerian red beans, and balti lobia are all diverse meals that are enjoyed internationally (Baker Creek Heirloom Seeds, 2019). Exact in depth nutrition facts are provided at the end of the chapter as well as recipe tutorials.

Post Harvest Cowpea Pest Challenges and Solutions

and diseases can diminish an entire yield of cowpea even after harvest (Gómez, 2004). In Africa, cowpea crop yields are far below yield potential (yield which occurs at optimal research farms) despite millions of dollars invested in insecticide research (Gómez, 2004). However insecticides can be harmful to the environment and potential users (Gómez, 2004). Despite the side effects, insecticides still improve crop yields. Large scale farmers use insecticides to maximize production to their crops (Gómez, 2004). However, insecticides are costly for a poor farmer (Gómez, 2004). Africa suffers the worst cowpea field losses because of the lack of insecticide resources and lack of funds for farmers to purchase them (Gómez, 2004). In an attempt to reduce pests during grain storage of cowpea, farmers have been provided access to hermetic grain storage bags. These bags create a low oxygen environment in which fungal pathogens and insect pests die (Silva, 2018). The Purdue Improved Cowpea Storage (PICS) has proven to be a reliable source for eliminating pests over the duration of multiple seasons (Purdue University, 2019). At a low cost of $3 USD, this can be an effective investment for small and large scale farmers (Ndegwa, 2016). This innovation however was not a complete success. The bags did not completely isolate the crops from all pesticides and insects (Silva, 2018). The collection of moisture in the bag caused the growth of fungi which was damaging to the grain (Silva, 2018). Some bags would slowly deteriorate as well (Baribusta, 2014). Though there's some concerns, the bags offer significant pest and disease reduction at an affordable price for smallholder farmers.

Additional Cowpea Information

Three Major CGIAR Institutes that breed cowpea and have seedbanks to request seed: https://www.iita.org/wp-content/uploads/2016/06/Cowpea_field_guide_for_Burkina_Faso.pdf https://avrdc.org https://www.icrisat.org

Nutritional Facts per 100 g and Recipe Tutorials https://www.nutritionvalue.org/Cowpeas%2C_raw%2C_mature_seeds%2C_catjang_nutritional_value.html https://www.nutritionvalue.org/Cowpeas%2C_raw%2C_young_pods_with_seeds_nutritional_value.html https://turkishstylecooking.com/cowpea-dish-recipe.html https://www.youtube.com/watch?v=9gFf4vIH4tg https://www.youtube.com/watch?v=0z4G71c0HEc

IITA step by step field guide (from Burkina Faso): https://www.iita.org/wp-content/uploads/2016/06/Cowpea_field_guide_for_Burkina_Faso.pdf

Cultivation and Storage Methods https://www.youtube.com/watch?v=f8lHkEW0pQY https://www.youtube.com/watch?v=eQd9TE5EnhQ

Harvesting Methods https://www.youtube.com/watch?v=_PGQAkZDIXk https://www.youtube.com/watch?v=eIyMPe4Vsug

Purdue University Improved Crop Storage Bags https://www.purdue.edu/postharvest/purdue-improved-crop-storage-pics/

Food and Agriculture Organization of the United Nations http://www.fao.org/home/en/

References

1. Gómez, Carlos. “COWPEA - Food and Agriculture Organization.” Food and Agriculture Organization of the United Nations. Accessed November 11, 2019. http://www.fao.org/3/a-au994e.pdf.

2. ICRISAT. (2019, November 19). Retrieved November 20, 2019, from https://www.icrisat.org/.

3. Ishikawa, H. (2013). Cowpea field guide for Burkina Faso. Retrieved November 27, 2019, from https://www.iita.org/wp-content/uploads/2016/06/Cowpea_field_guide_for_Burkina_Faso.pdf.

4. Ndegwa, D., Michael, D., Groote, D., Gitonga, D., Zachary, D., Bruce, D., & Anani, D. (1970, January 1). Effectiveness and Economics of Hermetic Bags for Maize Storage: Results of a Randomized Controlled Trial in Kenya. Retrieved from https://ageconsearch.umn.edu/record/212524/.

5. Purdue University. (2019). Purdue Improved Crop Storage (PICS). Retrieved November 21, 2019, from https://www.purdue.edu/postharvest/purdue-improved-crop-storage-pics/.

6. Sheahan , C. M. Cowpea (Vigna unguiculata). U.S. Department of Agriculture: USAGov. Retrieved June 2012, from https://www.usa.gov/federal-agencies/u-s-department-of-agriculture.

7. Silva, M. G. C. (n.d.). Hermetic storage as an alternative for controlling Callosobruchus maculatus (Coleoptera: Chrysomelidae) and preserving the quality of cowpeas. Science Direct, 78, 27–31. Retrieved from https://www-sciencedirect-com.subzero.lib.uoguelph.ca/science/article/pii/S0022474X18300900

8. World Vegetable Center. (2019, November 13). Retrieved from https://avrdc.org/.