Chapters 2.14
2.14 - Cowpea-Maize Intercropping as a Biofertilizer Strategy
Mehtab Rai, University of Guelph,Canada
Suggested citation for this chapter.
Rai,M. (2022)Cowpea-Maize Intercropping as a Biofertilizer Strategy. In Farmpedia, The Encyclopedia for Small Scale Farmers. Editor, M.N. Raizada, University of Guelph, Canada. http://www.farmpedia.org
Benefits of Cowpea
Smallholder farmers in Sub-Saharan Africa increasingly face the challenge of low soil fertility, primarily due to nutrient depletion, a concerning situation further exacerbated by climate variability and irregularities (Vesterager, Nielsen, & Høgh-Jensen, 2008). Traditionally, the reliance on chemical fertilizers has been the go-to solution, yet this approach comes at a considerable cost, economically and environmentally. Ironically, a forward-thinking solution to these issues involves an innovative approach which reverts to ancient techniques. The intercropping of maize with cowpea (Vigna unguiculata) offers a sustainable alternative to chemical dependency, integrating traditional farming knowledge with contemporary agricultural strategies (Hani Saber Saudy, 2015).
Like many grain legumes, cowpeas possess the ability to convert atmospheric nitrogen into a form that is usable by plants, due to a symbiotic relationship with nitrogen-fixing bacteria in their root systems. This natural process enriches the soil with essential nutrients, allowing cowpeas to act as a biofertilizer, supplementing the surrounding soil and component crops with nitrogen through their roots. This process involves the decomposition of cowpea plant matter, which then releases nitrogen into the soil, benefiting nearby crops (Akter et al., 2022). As maize requires abundant nutrients, and nitrogen fertilizers are potentially unaffordable or inaccessible to smallholder farmers, cowpea intercropping acts as an effective, cheaper solution which simultaneously enhances productivity and financial return (Haruna et al., 2018). Cowpea is renowned as one of the most tolerant legume crops to drought, able to produce grain in regions with very low rainfall (Carvalho et al., 2019). In regions like the Upper West of Ghana, cowpea cultivation aligns well with a unimodal rainfall pattern ranging from 500-1200 mm between May and September. The sufficient precipitation during these months supports healthy cowpea production (Karikari et al., 2023).
Step-by-Step Guide for Cowpea-Maize Intercropping
1. Land Preparation – Proper soil preparation requires an environment for seeds to germinate and develop a root structure. Select a site with adequate annual rainfall (750-1100 mm preferred) for sufficient cowpea growth (Pastures Australia, 2008). Prepare soil by clearing unwanted weeds and incorporating organic matter with a depth of at least 75 cm of subsoil moisture (Pastures Australia, 2008). Select appropriate seed species of maize and cowpea, dependent on local climate conditions (Pastures Australia, 2008).
2. Planting Layout and Row Spacing – Implement a layout of one row of maize to one row of cowpea, spaced 80 cm apart, with cowpea rows either 40 cm or 20 cm apart, to minimize competition and enhance resource use (Biruk et al, 2021). This is critical to minimize competition for sunlight, water and nutrients between the crops, which can lead to a more efficient use of resources and higher yields (Biruk et al, 2021).
3. Planting and Crop Management – The initiation of cowpea growth is dependent on phosphorus in the soil, a crucial macronutrient needed for optimum growth and development. If soils are not believed to contain enough phosphorus, a recommendation of 125 – 250 kg/ha of superphosphate, or 50 – 100 kg/ha muriate of potash is suggested to kickstart the cowpea growth process. Sow cowpeas at a rate of 10-15 kg/ha under dryland conditions, 20-25 kg/ha in irrigated areas and higher rainfall areas. Plant seeds 3-6 cm deep to ensure good seed-soil contact (Pastures Australia, 2008).
4. Weed and Pest Management – Implement weed control measures in early growth stages, to minimize nutrient competition (Hani Saber Saudy, 2015). Monitor closely for common pests and diseases that can affect cowpeas, and manage accordingly (Pastures Australia, 2008).
5. Grazing and Harvesting – Timing the cutting of the cowpea crop optimally ensures that the plant has developed enough biomass for sufficient nitrogen fixation and regrowth potential. Essential cutting time for cowpea crop is at peak flowering, at about 70 – 90 days after sowing, then allow for potential regrowth of crop after grazing (Pastures Australia, 2008).
Benefits of Growing of Cowpeas as a Complementary Crop Alongside Maize
The integration of cowpea with maize in intercropping systems has demonstrably shown significant benefits in agronomic and economic terms. A study from Pakistan revealed a substantial increase in green fodder and crude protein yield, at 21% and 94%, respectively (Azim et al., 2000). In situ dry matter digestibility in this study was at a maximum in the test group of intercropped maize and cowpea at a 70:30 ratio (Azim et al., 2000). Meanwhile, research in the Savèlegu district of Ghana documented that the average intercropping with any of the 14 cowpea varieties tested over the 2-year period had better net return per hectare compared to sole cropping (Haruna et al, 2018). This intercropping method not only increases the yield of product, but also enhances fertility without the need for synthetic fertilizers, as cowpea is able to fix about 60% of its nitrogen from the atmosphere, amounting to 70 kg N ha-1 (Vesterager et al., 2008). Additionally, intercropped maize-cowpea has been observed to reduce weed biomass by 49.5% compared to sole maize, ultimately saving a fraction of the cultivated land (Hani Saber Saudy, 2015).
Socioeconomic Implications of Technology Adoption by Smallholder Farmers
The intercropping of cowpea and maize presents not only an agronomic advantage, but also provides a profound socioeconomic benefit for smallholder farmers. By adopting this method, farmers are met with a sustainable alternative to costly and ecologically damaging practices such as chemical weed and pest control (Hani Saber Saudy, 2015). This denial of chemical fertilizers in favour of crop diversification methods may be an economic risk in the short term, but enriches the local community with healthier land, to be utilized by future generations. From an economic perspective, the advent of cowpea-maize intercropping has been shown to increase the value of forage yield, providing larger quantity of higher quality crops, an appealing option for smallholder farmers, particularly in regions with agricultural limitations (Azim et al, 2000).
Critical Analysis
While cowpea-maize intercropping presents promising solutions to the contemporary challenges confronting farmers in Sub-Saharan Africa, its successful implementation is dependent on addressing several critical considerations. Primarily, farmers must receive adequate education and training to ensure optimal crop spacing for optimal growth and yield (Biruk et al, 2021). Insufficient knowledge about the technology or ineffective implementation strategies may lead to competition for resources such as nutrients, water and sunlight, that may occur if intercropping is not done to a higher degree of efficiency.
Additionally, the success of cowpea-maize intercropping is reliant on the availability of phosphorus in the soil (Pastures Australia, 2008). Cowpea, a leguminous crop, requires phosphorus for its growth, which might be troubling for farmers in arid regions, unable to obtain the required fertilizer to initiate the regrowth of their land due to high costs, lack of availabilities, or simply, lack of awareness on its need (Mohammed et al., 2020).
The cultural acceptability of cowpea consumption is an overlooked aspect of this practice. This plays a crucial role in the adoption and sustainability of cowpea-maize intercropping systems. If cowpea is not commonly consumed or preferred, farmers may be less inclined to grow the crop along with their maize, potentially limiting the technology’s impact.
In regions where cultural preferences may lean away from cowpea as a mainstay crop, farmers have the opportunity to enhance maize yields by instead adopting an alternate, yet effective practice such as rotating maize with cowpea, rather than intercropping, which would minimize cowpea yields according to the farmers preferences, while still enhancing subsequent growth. Specifically, rotating maize with cowpea naturally suppresses pest populations and disrupts disease cycles, a critical factor in sustainable crop management. Furthermore, this rotation strategy complements the benefits of intercropping by ensuring continuous enrichment of the soil, such that throughout its life cycle, cowpea releases fixed nitrogen upon decomposition, fostering fertile grounds for future maize growth (Horst & Härdter, 1994).
Conclusion
In conclusion, the integration of cowpea-maize intercropping presents a sustainable avenue for addressing the challenges of soil fertility and economic resilience in Sub-Saharan Africa. This analysis underscores the importance of local adaptation and education in implementing such agricultural practices. The success of this system is dependent on the role played by government bodies, agricultural agencies, and farming communities themselves, to overcome barriers related to knowledge, resource availability, and cultural preferences. To move forward and advance this sustainable agricultural practice, policies that facilitate widespread education, phosphorus-rich fertilizers, and robust markets for cowpea varieties. A collective action towards sustainable practices such as the intercropping of maize and cowpea will sow the seed of environmental stewardship for future generations to endlessly reap.
Practical Links to Get Started
https://www.accessagriculture.org/grow-row-row Educational resource that guides farmers on the effective intercropping of legumes and cereals, such as cowpeas and maize. Explains the benefits of row-by-row crop planting, showcasing practical steps and real-world applications. https://www.iita.org/cropsnew/cowpea/#1620977266711-6244d37e-7ec1
A comprehensive insight into the cowpea crop and its functional benefits. Discusses cowpea varieties, and up-to-date research. https://www.feedthefuture.gov/article/harnessing-gender-inclusive-research-to-improve-cowpea-crops-in-africa/
Emphasizes the importance of gender inclusivity in agricultural research and development. Features interesting information about newly developed cowpea varieties, with an aim to develop climate-resistant cowpeas. https://plants.usda.gov/DocumentLibrary/plantguide/pdf/pg_viun.pdf
USDA plant guide for cowpea, featuring the plant’s characteristics, ecological benefits, and practical uses in agriculture. https://youtu.be/J2wADi9Q2ik?si=sXbmYIuHr7CON9fH
Documentary video on YouTube offering an informative presentation of intercropping technologies, specifically focusing on maize and cowpea. This video highlights the numerous benefits provided by such agricultural practices, with a particular emphasis on the socioeconomic and productivity gains.
References
1. Akter Suhi A., Mia S., Khanam S., Hasan Mithu M., Uddin M.K., Muktadir M.A., Ahmed S., Jindo K. (2022). How does maize-cowpea intercropping maximize land use and economic return? a field trial in Bangladesh. Land. 11, 581. https://doi.org/10.3390/land11040581
2. Azim A., Khan A., Nadeem M., Muhammad D. (2000). Influence of maize and cowpea intercropping on fodder production and characteristics of silage. Anim Biosci. 13(6), 781-784. https://doi.org/10.5713/ajas.2000.781
3. Biruk, G., Awoke, T., & Anteneh, T. (2021). Effect of intercropping of maize and cowpea on the yield, land productivity and profitability of components crops in Bena-Tsemay Woreda, Southern Ethiopia. International Journal of Agricultural Research, Innovation and Technology, 11(2), 147–150. https://doi.org/10.3329/ijarit.v11i¬¬2.57268
4. Carvalho, M., Castro, I., Moutinho-Pereira, J., Correia, C., Egea-Cortines, M., Matos, M., Rosa, E., Carnide, V., & Lino-Neto, T. (2019). Evaluating stress responses in cowpea under drought stress. Journal of Plant Physiology, 241, 153001–153001. https://doi.org/10.1016/j.jplph.2019.153001
5. Hani Saber Saudy. (2015). Maize-cowpea intercropping as an ecological approach for nitrogen-use rationalization and weed suppression. Archives of Agronomy and Soil Science. 61(1), 1-14. https://doi.org/10.1080/03650340.2014.920499
6. Haruna, A., Kombiok, J.M., Mohamed, A.M., Sarkodie-Addo, J., Larbi, A., & Rahman, N.A. (2018). Profitability of cowpea intercropped with maize in West Africa Guinea Savanna. Journal of Agricultural Science, 10(11), 185. https://doi.org/10.5539/jas.v10n11p185
7. Horst, W. J., & Härdter, R. (1994). Rotation of maize with cowpea improves yield and nutrient use of maize compared to maize monocropping in an Alfisol in the Northern Guinea Savanna of Ghana. Plant and Soil, 160(2), 171–183. http://www.jstor.org/stable/42939464
8. Karikari, B., Maale, M. D., Anning, E., Akakpo, D. B., Abujaja, A. M., & Addai, I. K. (2023). Cowpea cropping systems, traits preference and production constraints in the upper west region of Ghana: farmers’ consultation and implications for breeding. CABI Agriculture and Bioscience, 4(1), 1–11. https://doi.org/10.1186/s43170-023-00159-1
9. Mohammed, S. B., Mohammad, I. F., Pangirayi, T. B., Vernon, G., Dzidzienyo, D. K., Umar, M. L., & Umar, S. (2020). Farmers' knowledge, perception, and use of phosphorus fertilization for cowpea production in Northern Guinea Savannah of Nigeria. Heliyon, 6(10), e05207. https://doi.org/10.1016/j.heliyon.2020.e05207
10. Pastures Australia. (2008). Cowpea – Vigna unguiculata [Factsheet]. Retrieved from https://keys.lucidcentral.org/keys/v3/pastures/Html/Factsheet%20-%20Cowpea.pdf
11. PlantVillage. (2024). Cowpea (Vigna unguiculata). Retrieved from https://plantvillage.psu.edu/topics/cowpea/infos
12. Vesterager, J.M., Nielsen, N.E. & Høgh-Jensen, H. (2008). Effects of cropping history and phosphorus source on yield and nitrogen fixation in sole and intercropped cowpea–maize systems. Nutr Cycl Agroecosyst. 80, 61–73. https://doi.org/10.1007/s10705-007-9121-7