Chapter 4.34
4.34 - Vetch as a cover crop for small scale farmers
Collyer Boyd, University of Guelph, Canada
Suggested citation for this chapter.
Boyd,C. (2022) Vetch as a cover crop for small scale farmers. In Farmpedia, The Encyclopedia for Small Scale Farmers. Editor, M.N. Raizada, University of Guelph, Canada. http://www.farmpedia.org
Introduction to Vetch
Subsistence and/or small-scale farmers frequently struggle to balance the trade-off of using higher amounts of nitrogen (N) fertilizer to sustain and enhance productivity and yields, at the expense of increased soil erosion. Fortunately, there is vetch (Yelverton, 2017) (see Figure 1), a cover crop that forms a symbiotic relationship with root bacteria that effectively converts atmospheric nitrogen gas into a usable form of nitrogen fertilizer for plants, resulting in improved soil fertility. This process is called biological nitrogen fixation. Vetch can be found on nearly every continent where weather permits, including areas with higher concentrations of small-scale farmers like Asia and some parts of Africa (Nyugen et al, 2020). Common vetch (Vicia sativa) and hairy vetch (Vicia villosa) among other vetch species are leguminous plants that have provide a plethora of benefits to crop production and sustainability, but also bring forth increased costs, challenges, and labor for small-scale farmers.
Benefits
The use of vetch as a cover crop by small-scale farmers can provide them numerous benefits that ultimately improve the yield and productivity of their crops. Firstly, as already noted, vetch can be used as a cover crop to add nitrogen (N) nutrients to the soil, reducing the need for fertilizer. Through nitrogen fixation, vetch is able to produce anywhere from 100 to 200 kg/ha of nitrogen (SARE, 2023). Another advantage of vetch is its adaptability to a variety of soil conditions such as clay and sand (SARE, 2023). This is especially beneficial to many African nation’s landscapes that comprise of sand and clay rich soils. Similar to other flowering plants, vetch flowers also contain nectar that attracts pollinators to the crop (SARE, 2023). In return, these pollinators (birds, bees, butterflies, etc.) act as predators towards pests that can otherwise be detrimental to crops and crop yields. Yet another advantage associated with vetch is its ability to withstand cold temperatures, which is extremely valuable considering it grows throughout the winter. Common vetch can withstand temperatures as low as -29 and hairy vetch as low as -34 degrees Celsius (-30 Fahrenheit) (Brillon, 2023). In addition to improving overall soil quality, vetch can be used to provide toxin-free pastures, hay, silage, and green manure for livestock. Vetch can provide livestock with high levels of protein relative to other forage crops, with protein levels in vetch ranging from 12-20% depending on the species (McKee and Schoth, n.d.). Similar to the soil, livestock also benefits from the nitrogen fixation, disease resistance, and diversity that vetch crops provide. Further benefits of vetch crops include protecting the soil from erosion and runoff while providing a barrier to deter weeds (Lea, 2023).
How to Grow and Recommendations
Timing of Sowing & Harvesting
In African nations, vetch commonly experiences its growth during fall, winter, and early-spring months, and matures in late spring and early summer (McKee and Schoth, n.d.). However, in cooler climate conditions that exist in some Asian countries, vetch grows in early spring and is ready to harvest by late summer or fall (McKee and Schoth, n.d.). Hairy vetch is recommended in cooler climate areas as it is more resistant to colder temperatures compared to other vetch species.
Soil Preparation
Generally, the seedbed should be prepared such that it is free of weeds, clumps of soil, and is well-drained (Cyganeria, 2022). Soil preparation for vetch is largely dependent on firmness or density of the soil. Clay rich soil, heavy weed growth, and firmly packed soil are factors that elevate the need for plowing (Mckee and Schoth, n.d.). However, in the absence of these factors, the seed bed only needs to be cultivated in order to plant vetch. This makes it ideal to plant vetch following a cultivated crop such as soybeans. In terms of seeding rate, vetch should be planted at a rate of 15-20 kg/ha if being drilled, or at a rate of 25-45 kg/ha (SARE, 2023). Exact seeding rates depend on the characteristics of the soil. For example, heavier soil with an elevated moisture level would require less seed and should therefore can be broadcasted at a rate closer to 25 kg/ha compared to 45 kg/ha which would be better suited for more dry seed beds. It is recommended to grow vetch in soils with a pH range of 6.0-7.0 but it can tolerate pH levels as low as 4.5 and as high as 8.2 (Crothers, 2022).
Step-By-Step
1. Prepare seedbed so it is free of weeds, clumps of soil, and is well-drained.
2. Begin broadcasting vetch seeds in recommended month(s) based on geographical climate as detailed above. Seeding at rate between 25-45 kg/ha (Can also plant with a nurse crop such as rye or oats)
3. Hand-pull (mower or crimper preferred if available) vetch leaves to kill the plant without the use of herbicides. This is done approximately 3 weeks prior to summer seeding.
4. Cut vetch plants are left in the soil to act as mulch.
Challenges/Constraints
The main challenges associated with vetch crops relate to weather and climate constraints. Vetch has a minimum annual rainfall requirement of about 300 mm to grow, as most species are not drought resistant. Therefore, vetch would not be productive in the Northern regions of Africa where they receive less than 250 mm of rainfall annually. Vetch grows best in areas of medium-high rainfall that regularly receive upwards of 750 mm of rainfall annually. With this being said, it should be noted that American vetch is drought tolerant but is significantly more expensive than common or hairy vetch. Additionally, vetch grows best in the sun compared to shady areas, especially hairy vetch. However, vetch can still be productive in partly shady environments that receive sunlight periodically throughout the day (Brillon, 2023). Although vetch does require sunlight, excessively hot environments are not favorable as it requires cool temperatures for the best development. Soil temperatures should be no higher than 24 degrees Celsius in order for vetch to grow (Lea, 2023). Assuming many small-scale and subsistence farmers do not have access to machinery in the form of drilling seeders, vetch seeds will need to be planted using the broadcasting method. Broadcasting seed is much more labor-intensive and often leads to challenges regarding the consistency of seed distribution, depth, and compaction. Furthermore, as previously mentioned, broadcasting seed requires as much as double the seeding rate (25-40 kg/ha) compared to drilling (15-20 kg/ha), leading to increased costs of seed and labor (SARE, 2023).
Price and Availability
Vetch seeds can be obtained in African nations from organizations such as East African Seed, Syngenta, and the Seed Co Group as examples. Vetch seeds are often sold at $2 to $3 per pound of seed but can be cheaper, especially if bought in bulk. One supplier is currently offering 5 kg (~11 lbs) of seed for 750 South African Rand (~$40 USD). This would equal approximately $3.60 per pound of seed or $8 per kg. Based on this calculation, a subsistence farmer with a field equal to 1 hectare would need to spend $200-$320 to sufficiently broadcast seed the whole field which is expensive – therefore alternative seed distribution methods are needed including local farm cooperatives involving farmers bulking and re-using vetch seed. In addition to the cost of seeds, farmers will also have to perform or pay for the labor of sowing and harvesting. Fortunately, no labor or maintenance is required during the months of growing.
Conclusion
Vetch can be a very effective cover crop for small-scale and subsistence farmers while providing them with various additional benefits. The benefits far outweigh the challenges associated with growing vetch, as long as you reside in a favorable climate. African nations that receive little rainfall and experience hot climates regularly would not be optimal locations for growing vetch. However, small-scale farmers who live in environments with sandy, clay, or moist soil, medium-high rainfall annually, and optimal pH levels can reap the benefits from vetch crops. Essentially, small-scale farmers who live in areas that compliment vetch growth should implement it into their crops as a cover crop to improve soil composition and fertility, livestock well-being, and crop yields – as long as seed costs can be lowered.
Practical Links & Resources to get Started
Wild Food: Common Vetch (youtube.com) https://www.youtube.com/watch?v=1QpcQWtUoLQ
Video Identifying vetch and its Common Features Common Vetch | Sustainable Agriculture Research & Education Program (ucdavis.edu)
https://sarep.ucdavis.edu/covercrop/commonvetch Website containing all relevant information & guide to common vetch icm12.pdf (fao.org)
https://www.fao.org/fileadmin/user_upload/agp/icm12.pdf Information on seed production and ways to use vetch (39-40) Recarbonizing global soils – A technical manual of recommended management practices (fao.org)
https://www.fao.org/3/cb6598en/cb6598en.pdf Manual for vetch as a cover crop Training manual for ORGANIC AGRICULTURE (fao.org)
https://www.fao.org/fileadmin/templates/nr/sustainability_pathways/docs/Compilation_techniques_organic_agriculture_rev.pdf Information on cover crops Cover Crop Fact Sheet Hairy Vetch
https://covercrop.org/wp-content/uploads/2016/05/hairyvetch.pdf Hairy vetch extension manual Housing Supply | Mirror (:15) (youtube.com)
https://www.youtube.com/watch?v=5sNPIAWb0ys Video on how to grow vetch Vetch - Vicia sativa Seeds | Seeds for Africa
https://www.seedsforafrica.co.za/products/vetch-vicia-sativa-biomass-green-manure-cover-crop?variant=29606244876348 African Seed supplier
Seeds | Syngenta https://www.syngenta.com/en/seeds Seed supplier
?Figure 1. Photo Example of a Vetch plant
By Didier Descouens - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=105057789
References
1. Brillon, K. (2023, July 24). Hairy vetch: A pollinator plant and great cover crop. Epic Gardening. Retrieved from https://www.epicgardening.com/hairy-vetch/
2. Clark, A. (2020, August 4). Impact of cover crops on natural enemies and pests. SARE. Retrieved from https://www.sare.org/publications/cover-crops/ecosystem-services/impact-of-cover-crops-on-natural-enemies-and-pests/
3. Crothers, L. (2021, March 22). Common vetch. Sustainable Agriculture Research & Education Program, University of California, Davis Retrieved from https://sarep.ucdavis.edu/covercrop/commonvetch
4. Cyganeria, M. (2022, October 18). Growing hairy vetch: How to plant and raise this marvelous cover crop. Morning Chores. Retrieved from https://morningchores.com/growing-hairy-vetch/#:~:text=Ideally%2C%20vetch%20prefers%20sandy%2C%20well-drained%20soil%20with%20a,you%E2%80%99re%20planting%20before%20winter%20as%20a%20cover%20crop.
5. Lea. (2023, November 3). Hairy vetch cover crop: Benefits, planting guide, and maintenance. LeafyBackyard. Retrieved from https://www.leafybackyard.com/hairy-vetch-cover-crop-benefits-planting-guide-and-maintenance/
6. Luan Pierre Pott, Telmo Jorge Carneiro Amado, Raí A. Schwalbert, Fábio H. Gebert, Geovane B. Reimche, Luciano Z. Pes, & Ignacio A. Ciampitti (2020, December 9) Effect of hairy vetch cover crop on maize nitrogen supply and productivity at varying yield environments in Southern Brazil. Science of The Total Environment, 759. Retrieved from https://www.sciencedirect.com/science/article/abs/pii/S004896972037844X?fr=RR-2&ref=pdf_download&rr=8715c2ee6e7239e1
7. Nguyen, V., Riley, S., Nagel, S., Fisk, I., & Searle, I. R. (2020, June 19). Common Vetch: A Drought Tolerant, High Protein Neglected Leguminous Crop With Potential as a Sustainable Food Source. Frontiers in Plant Science, 11, 818. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7316993/
8. McKee, R., & Schoth, H. A. (n.d.). Vetch Culture and Uses. Retrieved from https://upload.wikimedia.org/wikipedia/commons/0/00/Vetch_culture_and_uses_%28IA_CAT10306100%29.pdf
9. SARE Outreach (Ed.). (2023, July 10). Managing Cover Crops Profitably, 3rd Edition: Hairy vetch. SARE. Retrieved from https://www.sare.org/publications/managing-cover-crops-profitably/legume-cover-crops/hairy-vetch/
10. Yelverton, F. (2017, November 27). Common vetch: NC state extension publications. Common Vetch | NC State Extension Publications. Retrieved from https://content.ces.ncsu.edu/common-vetch#:~:text=Common%20vetch%20%28Vicia%20sativa%29%20is%20a%20trailing%20winter,arise%20from%20fibrous%20roots%2C%20and%20flowers%20are%20purple.
11. Zotarelli, L., Avila, L., Scholberg, J. M. S., & Alves, B. J. R. (2009, March). Benefits of Vetch and Rye Cover Crops to Sweet Corn under No-Tillage. Agronomy Journal, 101(2), 252-259. Retrieved from https://acsess-onlinelibrary-wiley-com.subzero.lib.uoguelph.ca/doi/epdf/10.2134/agronj2008.0033x