Cowpea (Vigna unguiculata) is an annual leguminous crop, extensively cultivated for its ability to thrive in nutrient-poor sandy soils and in regions with limited rainfall, such as semi-arid areas. This plant is capable of biological nitrogen fixation in the soil through their root nodules, thus, making it immensely valuable for resource-poor farmers and ideal for intercropping with other crops. Due to its high adaptability, cowpea is a highly sought-after crop that serves various purposes. It can be used as a source of human food, providing nourishment to communities. Additionally, it serves as fodder for livestock, aiding in the sustenance of farm animals. Moreover, it can be planted as a cover crop, effectively shielding, and preserving the soil against erosion and degradation. Notably, very few crops have been discovered so far that offer such versatile applications.

Historical perspective

Cowpea cultivation can be traced back to ancient times, as far back as 300 B.C., originating in Africa. Over the centuries, cowpea became an essential component of African diets due to its adaptability to diverse growing conditions and its exceptional nutritional value. As a result of the African diaspora during the transatlantic slave trade, cowpea spread to different parts of the world, including Asia, the Americas, and Europe (Wight, 1907; Perrino et al., 1993).

Diversity of Cowpea Seeds

Cowpea seeds exhibit a weight range of 8 to 32 mg and come in two distinct shapes: round and kidney shaped. The pods are cylindrical and can be either curved or straight, containing a varying number of seeds, typically between 8 and 15 seeds per pod. The seed coat also displays a diverse array of colors, including white, cream, green, buff, red, brown, and black (Timko et al., 2007).

Importance as Food

Cowpea is not only a staple food crop but also a nutritional powerhouse. Data indicates that cowpea seeds contain protein (24%), dietary fiber (11%) and potassium (1112 mg/100 g) while low in lipids (less than 2%) and sodium (16 mg/100 g) (USDA, 2021). Studies have also shown that cowpea contains protein fractions of globulin, albumin, glutelins and prolamins (Teka et al., 2020). These indicate that consumption of cowpea can aid in combating malnutrition, particularly in regions where protein deficiency is a prevalent concern. However, in traditional cuisines, cowpea is used in a myriad of delicious ways, such as soups, stews, curries, salads, and even ground into flour for making cakes and bread. Moreover, cowpea leaves are edible and highly nutritious, contributing to the overall health and wellbeing of individuals.

Enhancing Livestock Nutrition

Apart from being a valuable food source for humans, cowpea also serves as an exceptional fodder crop for livestock. The leaves, stems, and pods of cowpea plants are highly palatable to animals and offer a balanced blend of essential nutrients, crude proteins, and digestible dry matters. When included in animal diets, cowpea improves the overall nutrition of livestock, leading to healthier and more productive animals. For example, in controlled sheep feeding experiments, researchers observed that when 200–400 g per day of cowpea haulms were added as a supplement to a basal diet of sorghum stover, the average live weight gain per animal was approximately 80 g per day. This finding highlights the positive impact of including cowpea haulms in the diet, as it led to an increase in the sheep's weight gain. The results indicate that cowpea haulms can be an effective and beneficial addition to the sheep's diet when aiming to enhance their live weight gain (Singh et al., 2003).

Shop Products That Include Cowpea Seeds

Use as a Green Manure Crop

Cowpeas are an excellent choice for green manuring due to their profuse ability to fix nitrogen in the soil through their root nodules. When properly inoculated in nitrogen-deficient soils, cowpeas can even surpass 300 lb. of nitrogen per acre. For optimal results, it's essential to consider the moisture levels and soil nitrogen content. In cases where there is higher moisture and more soil nitrogen, cowpeas tend to prioritize vegetative growth over seed production. However, unlike many other grain legumes, cowpeas can leave a net gain of nitrogen in the field even after the seeds are harvested. Cowpeas are thus an excellent choice for increasing soil fertility and supporting sustainable agriculture practices (SARE, 2007).

Importance as a Cover Crop

Cowpea as a cover crop can provide multiple soil benefits. Some of them are as follows:

• 1. Nitrogen Fixation: One of the significant advantages of cowpea as a cover crop is its ability to fix atmospheric nitrogen into the soil. Cowpea forms a symbiotic relationship with nitrogen-fixing bacteria called rhizobia, which reside in specialized root nodules. These bacteria convert atmospheric nitrogen into a form usable by plants, thereby enriching the soil with this essential nutrient. When cowpea residues decompose after termination, the stored nitrogen becomes available for subsequent crops, reducing the need for synthetic nitrogen fertilizers.
• 2. Soil Improvement and Erosion Control: Cowpea's extensive root system helps in improving soil structure and fertility. The roots penetrate deep into the soil, breaking up compacted layers, enhancing water infiltration, and promoting better aeration. As a result, the soil becomes more conducive to root growth and nutrient uptake by other crops in rotation. In addition, the dense cover provided by cowpea helps prevent soil erosion caused by wind and water. The plant's foliage and root system anchor the soil, reducing the risk of topsoil loss and maintaining its fertility.
• 3. Weed and Pest Suppression: Cowpea's rapid and dense growth inhibits the emergence, germination, and growth of weeds. Intercropping with cowpea in dryland farming systems has been shown effective in suppressing weeds (Lee & Thierfelder 2017). Additionally, cowpea can also reduce the abundance of plant pathogenic nematodes in soil (Wang & McSorley 2018).

In conclusion, cowpea is an exceptional legume that holds historical significance and continues to be of paramount importance in modern agriculture. Its versatile use makes it a crucial component in global food security efforts and sustainable farming practices.

Written By Siddhartha Shankar Bhattacharyya Texas A&M University Soil and Crop Sciences Student

If you are interested in winning a $5,000 scholarship towards higher education in an agriculture related field, check out our scholarship page for more information. Our scholarship program started back in 2016 in honor of our founder Demetrios Agathangelides. Demetrios immigrated to the United States from Greece and attended Utah State University, graduating with a degree in Plant Science. With a love of seeds and an appreciation for education he continued to teach in seminars and local talk shows. Today we honor him by awarding a scholarship to a deserving student in the agricultural sciences.

References

• Lee, N., & Thierfelder, C. (2017). Weed control under conservation agriculture in dryland smallholder farming systems of southern Africa. A review. Agronomy for Sustainable Development, 37(5), 48.
• Perrino, P., Laghetti, G., Spagnoletti Zeuli, P. L., & Monti, L. M. (1993). Diversification of cowpea in the Mediterranean and other centres of cultivation. Genetic resources and crop evolution, 40, 121-132.
• SARE. (2007). Managing Cover Crops Profitability. https://www.sare.org/publications/managing-cover-crops-profitably/legume-cover-crops/cowpeas/
• Singh, B. B., Ajeigbe, H. A., Tarawali, S. A., Fernandez-Rivera, S., & Abubakar, M. (2003). Improving the production and utilization of cowpea as food and fodder. Field crops research, 84(1-2), 169-177.
• Teka, T. A., Retta, N., Bultosa, G., Admassu, H., & Astatkie, T. (2020). Protein fractions, in vitro protein digestibility and amino acid composition of select cowpea varieties grown in Ethiopia. Food Bioscience, 36, 100634.
• Timko, M.P., Ehlers, J.D., Roberts, P.A. (2007). Cowpea. In: Kole, C. (eds) Pulses, Sugar and Tuber Crops. Genome Mapping and Molecular Breeding in Plants, vol 3. Springer, Berlin, Heidelberg.
• USDA. (2021). Food Data Central. https://fdc.nal.usda.gov/
• Wang, K. H., & McSorley, R. (2018). Management of Nematodes with Cowpea Cover Crops. ENY-712. Gainesville: University of Florida Institute of Food and Agricultural Sciences.
• Weng, Y., Ravelombola, W. S., Yang, W., Qin, J., Zhou, W., Wang, Y. J., ... & Shi, A. (2018). Screening of seed soluble sugar content in cowpea (Vigna unguiculata (L.) Walp). American Journal of Plant Sciences, 9(7), 1455-1466.
• Wight, W. F. (1907). The history of the cowpea and its introduction into America (Vol. 102, pp. 43-59). Washington, DC, USA: US Government Printing Office.