Chapters 2.12
2.12 - Intercropping Wheat and Green Peas for Smallholder Farmers
Zixian Lee , University of Guelph,Canada
Suggested citation for this chapter.
Lee,Z.(2022)Intercropping Wheat and Green Peas for Smallholder Farmers . In Farmpedia, The Encyclopedia for Small Scale Farmers. Editor, M.N. Raizada, University of Guelph, Canada. http://www.farmpedia.org
Introduction
To address the escalating costs and accessibility of synthetic fertilizers, smallholder farmers may face a big challenge in maintaining soil fertility to ensure crop yields (Matusso et al., 2012). This issue is especially relevant to developing regions where farmers have financial constraints. Intercropping is an agricultural method of growing two or more crops in proximity (Matusso et al., 2012), which provides farmers a sustainable and cost-effective alternative to conventional agricultural practices. This article will demonstrate the viability of intercropping wheat and green peas, which are a common cereal-legume intercropping combination, to enhance soil nitrogen level and overall farm productivity, hence profitability, particularly for smallholder famers.
The primary reason for intercropping wheat and green peas is because of their complementary nutrient use (Bedoussac & Justes, 2010). As a leguminous plant, green peas have the unique ability to capture nitrogen from the atmosphere and convert it into a form that plants can use for growth. This process can be made through a partnership with a type of bacteria called Rhizobia (Matusso et al., 2012). These bacteria live inside small growths on the pea plant's roots, known as nodules. Inside these nodules, the bacteria work like a natural fertilizer factory, transforming atmospheric nitrogen into nutrients that help the green peas thrive (Matusso et al., 2012). This process, which is called biological nitrogen fixation, can also benefit cereal plants, which require a large amount of nitrogen but cannot fix nitrogen from the atmosphere on their own. Notably, green peas can increase the contribution of nitrogen fixation to the total nitrogen accumulation of wheat-pea intercropping compared to a pea sole crop (Pelzer et al., 2012). As a result, the yield of wheat and soil nitrogen accumulation can be increased without adding chemically synthesized fertilizer (Ghaley et al., 2005).
Implementation (Tips to Get Started)
To effectively implement wheat and green pea intercropping, farmers should adopt specific cultivation techniques for optimal growth and yield. The approach involves organizing the crops in alternating rows, a strategy known as strip intercropping, to harness their complementary nutrient uses efficiently. For row spacing, it is advisable to reduce the wheat's seeding rate by 10-25% to prevent overcrowding, ensuring green peas receive enough sunlight for effective biological nitrogen fixation (Matusso et al., 2012). This adjustment is critical for the peas' ability to enrich the soil and support both crops. Additionally, a dense legume canopy can naturally suppress weed growth by limiting sunlight penetration to the soil, thus mitigating competition for essential resources like sunlight and water (Matusso et al., 2012). Moreover, the application of a mineral fertilizer containing phosphorus may be necessary if the soil's phosphorus levels are low, to aid in the initial growth stages of both plants (Matusso et al., 2012). By adhering to these cultivation recommendations, farmers can maximize the intercropping benefits, such as enhanced soil fertility, reduced dependency on chemical fertilizers, and effective weed management.
Benefits
The major benefit that intercropping can bring to smallholders is financial. This is because properly implemented intercropping significantly boosts the yield efficiency, which can be assessed by the land equivalent ratio (LER). This metric describes the land needed to achieve the same yield from monoculture versus intercropping. A study showed that the LER of intercropping wheat and green peas was greater than 1, indicating more efficient land use (Sheha et al., 2015). This study also showed that intercropping peas with wheat increased net returns to between US$ 1,764 and US$ 2,890 per hectare, compared to US$ 311 per hectare for sole wheat. The most profitable scenario was planting peas on October 1st with wheat receiving 133.8 kg of nitrogen per hectare (Sheha et al., 2015). These findings showed that the intercropping strategy was much more profitable compared with growing wheat alone. This profitability not only came from higher yields, but also from reduced input of chemically synthetic fertilizer, thanks to the nitrogen fixing ability of green peas (Ghaley et al., 2005).
Additionally, green peas are able to utilize the vertical space above the wheat due to their climbing vining growth habit, which allows them to capture sunlight that would otherwise be wasted. This spatial arrangement leads to a dynamic complementary, where the leaf area index of one crop compensates for the other at different growth rate (Bedoussac & Justes, 2010). Bedoussac and Justes (2010) also indicated that such arrangement can lead to a 10% increase in the light utilization rate for the intercropped system.
Moreover, intercropping exhibited growth complementarity and better nitrogen acquisition dynamics (Bedoussac & Justes, 2010). Before wheat flowering, green peas have a higher growth rate, providing an early canopy that can cover the soil to restrict weed germination. Meanwhile, the wheat benefits from the nitrogen fixed by green peas, resulting in an improved growth rate and a potential increase in the wheat's nitrogen status by an average of 14% (Bedoussac & Justes, 2010). This synergy between wheat and green peas ensures resources, such as nitrogen and sunlight, are efficiently utilized throughout the growth period.
Critical Analysis
Despite the fact that intercropping can bring lots of benefits to smallholder farmers, there are also many challenges pointed out by Mamine and Fares in 2020 that people need to consider before implementing intercropping. First of all, the transition from sole crop to intercropping can be overwhelming due to the need for specific knowledge and tools. For example, machinery designed for monocultures may not work well for the precise requirements of intercropping. Additionally, more education needs to be given to smallholders since intercropping requires more knowledge than sole cropping. Secondly, although smallholders can save money on fertilizers, other costs, which include the cost of seeds, weed/pest control, sowing, collection, storage (which poses a higher risk of developing mycotoxins), sorting (crop lost during separation), could potentially leverage the savings from fertilizers and result in a higher overall production cost (Mamine & Fares, 2020). Thirdly, some industrial buyers have a preference for buying monocultured wheat because the protein content of intercropped wheat is sometimes not stable. At last, Matusso et al. (2012) also mentioned that soil acidity and phosphorus scarcity could pose huge problems to smallholders because these conditions will weaken the nitrogen fixation ability of legumes, thereby reducing their ability to enrich soil nitrogen. Additionally, the minimal application of mineral fertilizer by smallholders exacerbates this issue (Matusso et al., 2012). This soil condition is prevalent in many areas of Sub-Saharan Africa and Southeast Asia, regions where many smallholders reside (Matusso et al., 2012).
Another approach, rotation cropping of peas-wheat, could also be beneficial to smallholders, as it offers distinct advantages in terms of pest, disease and weed management. The absence of a host crop for one season broke the life cycle of many pests and diseases, which suppressed their populations without chemical interventions (Stevenson & van Kessel, 1996). Moreover, this approach can also increase wheat seed yields and soil nitrogen (Stevenson & van Kessel, 1996), which are similar benefits provided by intercropping. However, intercropping can significantly increase net returns as mentioned before. Therefore, the choice between these two approaches is dependent on specific farm objectives, such as maximizing profit versus long-term weed/pest/disease management.
In conclusion, the practice of intercropping wheat and green peas presents smallholder farmers with a viable strategy to bolster farm productivity and soil nitrogen levels, which are key for agrarian communities in developing regions. This cultivation method harnesses the complementary nutrient needs and benefits of these crops, exploiting the peas' natural nitrogen-fixing ability to benefit wheat growth. As demonstrated by increased land use efficiency and economic returns, intercropping stands out as a financially advantageous approach. However, the transition to intercropping demands careful consideration of the challenges, such as soil acidity and phosphorus scarcity, particularly in regions like Sub-Saharan Africa and Southeast Asia. Furthermore, the choice between intercropping and rotational cropping of peas and wheat depends on balancing immediate financial gains against long-term benefits, including improved pest and disease management. Despite the challenges, with appropriate strategies like adjusted row spacing, effective weed control, and judicious fertilizer use, intercropping can offer smallholder farmers a pathway to enhanced productivity and sustainability.
Practical Links to Get Started
Click https://www.youtube.com/watch?v=0gCh89_4Jzo for general information about intercropping!
Click https://www.youtube.com/watch?v=ST_1WTWVpQ0 for an intercropping trial.
Click https://www.fao.org/3/i5310e/i5310e.pdf for “Save and Grow”!
References
1. Bedoussac, L., & Justes, E. (2010). Dynamic analysis of competition and complementarity for light and N use to understand the yield and the protein content of a durum wheat–winter pea intercrop. Plant and Soil, 330, 37-54. https://doi.org/10.1007/s11104-010-0303-8.
2. Ghaley, B., Hauggaard-Nielsen, H., Høgh-jensen, H., & Jensen, E. (2005). Intercropping of wheat and pea as influenced by nitrogen fertilization. Nutrient Cycling in Agroecosystems, 73, 201-212. https://doi.org/10.1007/s10705-005-2475-9.
3. Mamine, F., & Farès, M. (2020). Barriers and levers to developing wheat–pea intercropping in Europe: A Review. Sustainability, 12(17), 6962. https://doi.org/10.3390/su12176962
4. Matusso, J. M. M., Mugwe, J. N., & Mucheru-Muna, M. (2012). Potential role of cereal-legume intercropping systems in integrated soil fertility management in smallholder farming systems of sub-Saharan Africa. Kenyatta University, Agricultural Resources Management Department. http://repository.ruforum.org/system/tdf/Matusso%2C%20J.M.M%20et%20al.pdf?file=1&type=node&id=32039
5. Pelzer, E., Bazot, M., Makowski, D., Corre-Hellou, G., Naudin, C., Al Rifaï, M., Baranger, E., Bedoussac, L., Biarnès, V., Boucheny, P., Carrouée, B., Dorvillez, D., Foissy, D., Gaillard, B., Guichard, L., Mansard, M.-C., Omon, B., Prieur, L., Yvergniaux, M., … Jeuffroy, M.-H. (2012). Pea–wheat intercrops in low-input conditions combine high economic performances and low environmental impacts. European Journal of Agronomy, 40, 39–53. https://doi.org/10.1016/j.eja.2012.01.010
6. Sheha, A., Abdel-Wahab, T., & Abdel-Wahab, S. (2015). Maximizing nitrogen and land use efficiencies of intercropped wheat with pea under different pea sowing dates. Journal of Plant Sciences, 3, 358. https://doi.org/10.11648/J.JPS.20150306.20.
7. Stevenson, F., & Kessel, C. (1996). A landscape-scale assessment of the nitrogen and non-nitrogen rotation benefits of pea. Soil Science Society of America Journal, 60, 1797-1805. https://doi.org/10.2136/SSSAJ1996.03615995006000060027X.